JC007: Drilling the Mid-Atlantic Ridge


 JC007



Question time!


The Q&A service is no longer available as the cruise has finished.
Scroll down to see some of the questions and answers from the cruise.



Q

Do any of you dive?If you do then do any of you get scared down deep?

Thank you!

Jessie Boley, Ohio

A

None of us are skin divers, and you can’t free dive to this depth.  However, manned research submersibles routinely dive on mid-ocean ridges.  Some of the earlier work in this area was carried out by a French diving programme.  I have dived a number of times in a submersible  - in the American Alvin in the Eastern Pacific, in the French Nautille near Easter Island, and south of South Africa in a Japanese sub.  All of them are quite similar, and carry three people (one or two pilots and two or one scientists) in a sphere 2 m wide (about the size of a very small car). It can get a bit cramped, but usually it is too busy (and exciting!) to get scared.  The first time I dived I thought I might find it claustrophobic, but once we had started I didn’t really think about it any more.  Your first view of the seafloor is magical – it’s like being inside a giant aquarium, and often you have the added thrill that no-one has seen this particular place before.

ROGER


Q

How deep is the water you are working in?  I live in West Texas and heard about your voyage on PBS.  Checking on voyage daily.  Favorite saying " just think what your are going to know tomorrow."

Jay Jennings

A

The seafloor here is between about 2000 metres and 5000 metres (about 1 – 3 miles).

ROGER


Q

Greetings. I am very interested with the project. I have a question I would like you to answer. What technology does the TOBI implement?

Lewis E. Varela, Texas

A

TOBI stands for Towed Ocean Bottom Instrument, and is actually a towed vehicle that can carry a number of different sensors.  The prime one is side-scan sonar.  This is a bit like an echo-sounder turned on its side: the sound beam is emitted almost horizontally, and returns echoes progressively later from more distant points on the seafloor, out to its maximum range of 3 km. Rough or hard seafloor (solid rock) produces stronger echoes; smooth, soft seafloor (sediment) gives much weaker ones, so we can build up a sonar image which is a bit like an aerial photograph.  The sound is emitted and received by transducers – an underwater equivalent of loudspeakers and microphones, and it uses a frequency of 30 kHz – about twice the maximum audible range (say, twice the frequency of a high-pitched bird song).

Another important instrument for us is a magnetometer.  This records tiny variations in the strength of the Earth’s magnetic field that result from the very tiny natural magnetization of rocks.  These record the reversals of the Earth’s field direction through time (north and south magnetic poles switch direction every few hundred thousand years), and help us date the rocks and work out the speeds of plate motions. 

We also have a sub-bottom profiler (similar to an echo-sounder, but with a frequency of signal that can penetrate the sediments of the seafloor and is reflected from the hard rock underneath, measuring the sediment thickness.

Finally we have a set of instruments for measuring properties of the water: temperature, salinity (amount of dissolved salt) and light transmission.  These can show the presence of hydrothermal vents, such as the famous “black smokers”.

All in all, TOBI is a pretty sophisticated vehicle, and I often think that studying the ocean floor is similar in technological challenge to exploring space.

ROGER


Q

As far as I can assertain, you are cruising at the conjunction of the North American, African and European plates.  Is this perhaps the cause of there not being any crust at this point? There have been a few earthquakes on the Mid Atantic ridge the past few weeks. Does this do anything to your testing equipment?

Jeanette Liddle, Illinois

A

Good question, Jeanette, and well spotted!  We are indeed near this supposed “triple junction” (though actually it is North America/South America/Africa junction).  Because the relative plate motion between North and South America is so low (about 2 mm per year), the precise position is not well established, but it possibly lies about 70 km to the west of us where there is a zone of earthquake activity.  We have discussed whether this boundary could be affecting the missing crust, but at present we are unsure.  Unless there was a very large earthquake very near by it would not affect us.  Our sonar is sensitive to very high frequencies (30 kHz or about twice the top of the human audible range), much higher than most energy emitted by earthquakes.

ROGER


Q

What does TOBI stand for? Thanks for a brilliant insight to the project.

Stephen Donovan, Essex

A

TOBI stands for Towed Ocean Bottom Instrument, and is actually a towed vehicle that can carry a number of different sensors.

ROGER


Q

Well done on the trip so far, I'm following your trip with great interest .  But I wonder how your drill is secured on the ocean floor while you drill?  could you please explain.  Enjoy the rest of the trip.

Paul, Kent

A

Dear Paul - It just sits there under its own weight – just less than a ton.

ROGER


Q

Your expedition sounds very exciting and looks like everybody will be kept very busy. 
When you start drilling into the mantle, how fast and how much do expect the temperature to rise in the drill hole?  How do you measure the temperature? Thermocouple? How do you know if the bit breaks?


Tom Jennings, New York

A

In answer to your questions as we are only drilling one meter into the seabed the only real temperature rise at the drill bit is from the friction during cutting. This is cooled by means of a centrifugal pump that sucks in seawater and pumps it down the drill barrel. Temperatures at the drill are measured but not at the bit. If the bit breaks the drill will jam and we then need to recover the drill. The drill bit is a diamond set bit.

IAIN


Q

Do you have any other websites that may be useful for information on this topic? Are there any photographs of this chunk missing? My father mentioned something about this to me yesterday and I want to find out as much as possible to share with  him.  Will you have a real-time link to the data and/or images you will be discovering when you explore this region(s)?
Thanks for your scientific study of our planet. Your studies are important to each human on this planet. I wish you and your team the best in your discoveries of our Earth. Have a wonderful day.
thanks again,


Carl, Fresno

A

British Geological Survey   http://www.bgs.ac.uk/

Integrated Ocean Drilling Program  http://www.iodp.org/

European Science Operator  http://www.eso.ecord.org/


Q

When can we see the footage of the sea floor?  What about the drilling samples?  How deep within the mantle will the samples be taken?

Tracey Catt, USA

A

This drill can take sample up to 1 meter. Although we have other remote drill that can sample up to 15m. You can see images from the seafloor in the diary from 22 March.

Iain


Q

Hi there I am a 8th grade teacher here in Brighton (USA), we were wondering as a class how far you are going to actually be drilling into the earth below the sea?  Good luck from Brighton Co!

Eric Heinz, Colorado

A

Hello Eric

The drill we have onboard has a drill barrel 1 meter long and can recover an 800mm sample. This drill is rated to 5500m water depth. Other subsea drill can drill deeper but this one is the only one that can retrieve orientated core this is core that has a scribe mark along its length that can then be tied to onboard compass readings.

 Iain


Q

I am in my 3rd year of college and have been learning all about earth science and sea floor spreading is something I like the most, because of the recycling of the earth's material. Question: is the green layer described the mineral olivine that is exposed and if so, which type? Thank you for your work and research, by the way I am a Naval veteran and I know what sea life is like, on a carrier that is.

Richard Vann, west Vrigina

A

Hi Richard,

You’re right, the green rocks we’re getting are made mostly of the mineral olivine, or at least they were before they came into contact with seawater.  Because olivine is most stable and “happy” at high pressures and temperatures found within the earth’s mantle, it tends to alter to a different green mineral called serpentine when it comes into contact with cold seawater.  As you may know, the mineral olivine can have a range of compositions, which we write as (Mg,Fe)2SiO4.  The percentage of magnesium (Mg) vs. iron (Fe) depends on how much the mantle has melted, but mantle rocks always have a lot more Mg than Fe, so they are much closer to forsterite (the Mg-rich end-member composition of olivine) than to fayalite (the Fe-rich end-member).  Meanwhile, if you want a piece of mantle material, there are some pieces that got squished up into the Appalachian Mountains when they formed.  Ask your professor if he can recommend a road trip that will take you past some ultramafic roadcuts, and maybe you’ll get bonus points for being enthusiastic. :-)


Q

is it possible there may be new minerals due to the way the rocks have formed around this gaping hole and with the pressures of being deep under water?

Tomas, Lowestoft

A

Hi Tomas,

We probably won’t find any new minerals because, believe it or not, even the very high pressures deep at the bottom of the ocean are much much less than the pressures deep inside the earth!  This is because, in the earth way deep down beneath a mid-ocean ridge, all the rocks have water AND more rocks on top of them, whereas the ones on the seafloor just have water on top of them. 


Q

How many Sharks have you seen? Have you seen any bones? If you have how did they look? Thanks!!

Andrew Boley, aged 9, Ohio

A

Hi Andrew!

Well, we haven’t seen any sharks yet, but you can count on it that if we do, we’ll put up lots of pictures!  We haven’t found any real bones, either, but what we have found a lot of is little skeleton-like parts of underwater creatures like sea-fans.  When we dredge for rocks, sometimes we get these in our dredge basket as well.  They don’t look like much—most look like burnt sticks—but keep checking the “daily diaries” and maybe we can post some pictures for you.

Kay


Q

Hi, This mantle rock that you are dredging. Do you think it could have some metallurical uses or maybe used as a fuel or something.

Akshay, India

A

Hi Ashkay,

Sometimes mantle rocks get squeezed up on land (these exposures are called ophiolites), and sometimes people mine for chrome in these places.  It’s actually very difficult and expensive to get rocks from the seafloor, so for now it’s more economical to use exposures on land.


Q

Retired Organic Chemistry Prof. would like to know how you distinguish Mantle rock from Crust rock.

Prof. Otto Meth-Cohn, Northumbria

A

Hi Professor,

When the mantle partially melts, certain elements “prefer” to be in melt rather than in solid, and these elements become partitioned into the melt.  Since the melt is what eventually forms the crust, you end up with different compositions in the crust vs. the residual mantle.  These different compositions result in different minerals (or similar minerals but very different abundances).  For example, peridotites (mantle rocks) are generally made of (in decreasing order of abundance) olivine, orthopyroxene, clinopyroxene, and about 1% of some aluminous phase (plagioclase, spinel, or garnet depending on depth).  Basalts (crustal rocks), on the other hand, contain a lot more plagioclase (because aluminum is partitioned into melt, and plagioclase, as the lower-pressure aluminous phase, is what crystallizes at crustal pressures), and may or may not contain various amounts of pyroxenes and/or olivine.  Because the minerals are so different in these different kinds of rocks, we can tell which kind they are right away just by looking at the rocks.


Q

I find this particular piece of research facinating. What has been speculated as a likely reason crustal deposition is so much less here as other places and over such a large area?  How much of a differential in crust thickness is there between your location and other similar areas along the mid-atlantic ridge?  Are there spurious deep-water currents that would have interfered over time? Is the lack of crustal deposits only a carryover from times past or does the process continue today?

Steve, South Carolina

A

Hi Steve,

Usually, oceanic crust is thought to be 6-7 kilometers thick.  We don’t actually know the reason why the crust is missing here—that’s why we’re doing the research!  We do have a couple of hypotheses, though; the most likely is that the mantle didn’t melt enough to produce crust.  This could happen for because a) the mantle is colder here than is typical, or b) the mantle here might have melted billions of years ago and doesn’t have any melt ingredients left in it now.  Since material is still moving away from the ridge axis, we can tell which processes are still active today because they are still in evidence on the ridge axis—things that happened a long time ago have been carried off-axis.  Since we find mantle rock in the ridge axis here, we know that the processes that created the missing crust are still active today.  Currents don’t have much to do with the missing crust, because the currents on the seafloor are very gentle and don’t have the power to erode much, especially not 7 kilometers’ worth of material. 


Q

Hi Team, looking at the bathymetric image showing your location, I notice that there are fracture/stress? lines running at about 90 degrees across the ridge. What are these and why do the run across the ridge if the plates are moving away from the ridge? Reading your facsinating story on a daily basis. Kind regards.

Jo, South Africa

A

Hi Jo,

You are right that there are prominent features that trend at 90o to the ridge axis.  We call these features “fracture zones”, and they form because the ridge axis has offsets—that is, it takes periodic jogs to the east or west.  Because the ridge segments to the north and south of the offset are still spreading, the material immediately to the north and south of the offset is moving in opposite directions.  We call this a transform fault, and if you look at a world-wide map of earthquake occurrences, you’ll see that transform faults have lots of earthquakes where the plates are grinding past each other.  Once the plate material on both sides of the transform has moved sufficiently off-axis so that it’s all moving the same way, the earthquakes stop but the scars remain, so you can see the fracture zones far off-axis.


Q

There's rumors that you are looking for Atlantis.... or Lemuria... Are you? What percentage of the earths ocean floor has been explored?

Caleb Brown, aged 11, Minnesota

A

Hi Caleb,

We aren’t looking for any mysterious missing island, although it would be exciting if we were!  We just want to know why the normal ocean crust doesn’t seem to form in this part of the world.  As for how much of the Earth’s ocean floor has been explored, I can’t give you an exact figure, but I bet it’s less than 10%.  We have better maps of the surface of Venus than we have of the ocean floor because it is so difficult to “see” through water.  A couple of years ago there was actually an accident where a submarine crashed into an underwater mountain that wasn’t on any maps of the seafloor, so more underwater exploration is definitely needed!


Q

Are all of you looking forward to attaining your goals on this trip? How many of you are seasick this early into the trip? Have the seas been calm?

Rex Mullins, Missouri                          

A

Hi Rex, We are all really excited about the cruise, especially now that we have arrived at our main sampling location and can start getting some results back.  We have been very lucky and none of the scientific team have been seasick at all.  As for the seas they’ve been calm, the only time the ship rolls around a bit is when we are stationary and deploying instruments using the starboard side winch, this is because the ship becomes slightly unbalanced but it is not serious and life on board continues on as normal.

Michelle


Q

is it hard living on the ship?

Ty, Woodstock

         

A

Hi Ty, living on the ship is not hard, we are lucky in that this is the first scientific voyage that the James Cook has been on and so everything is new.  We are just coming up to 2weeks on board with another 4 to go, perhaps in a few weeks time the answer will be different!

Michelle  


Q

Will you also be looking at any possible living organisms inside this "hole".

Jay Knipper, San Antonio, USA

A

Hi Jay, We aren’t actually looking for any biological life, the main aim of our cruise is to try and understand how the ocean crust formed in these areas and so we are sampling the rocks and using towed instruments (TOBI) to map the area.

Michelle


Q

What time zone and date are used for the ship position in the diary?  Is that midnight at the beginning of the day described, or midnight at the end of the day?  And is the time zone the ship's time, or UTC/GMT, or something else?

Hal Mueller

A

Hi Hal, The positions that I give in my diaries are for midnight at the end of day listed, so the position I post is our last position of that day.  The times given are in GMT, although the ship is actually on GMT-3. 

Michelle

Q

Arent you worried that digging any further or disrupting the plate as is will trigger negative reactions from the plates?

Ray, Texas

A

Hi Ray, We are only drilling 1m into the seafloor and dredging samples from the slopes of the topography.  These are both very shallow and should not have any effect on the plates themselves. 

Michelle


Q

I notice you said you've gotten sea bottom rock samples by dredging.  How big is the dredge scoop and how much material does it bring up each time? And how far apart do you take each sample?

Tim, Texas                       

A

Hi Tim, The dredge scoop has a rectangular steel mouth with a chain net behind it with a pipe behind this at the end to trap any rock. In total the scoop is 60cmx30cm with 150cm of chain net, the pipe at the end is about 70cm long.  We choose our dredge sites by looking at bathymetric maps (maps of seafloor topography) and look for slopes, which we can pull the dredge up. How much rock you retrieve from a dredge is very variable, however it is often the quality of the samples we get back is more important rather than the number we retrieve.

Michelle


Q

I look at your site every day....Good job and very interesting. Could you possibly add some info on the ship and it's crew....Thanks,

Larry

A

Hi Larry, You’ve seen into our future plans……we’re putting together profiles of all the crew at the moment and will be posting a few each day in the daily diary over the next couple of weeks. Watch this space!

Michelle


Q

What kinds of marine life have you seen in the area? Any curious whales or whale sharks come close to the ship?

Don, Texas Gulf coast 

A

Hi Don, So far we have seen some dolphins, flying fush and dorado fish, we are hoping to see lots more over the coming weeks. A flying fish actually landed on the deck this evening!

Michelle


Q

Hi Guys. What is  your longitude and latitude? Have you seen any sea monsters, oar fishes? Is it really rough out there?  Did you have any big winds? Have you seen any submarines? Have you seen any monster waves?

THANKS!!

Pedro, age 12, USA

A

Hi Pedro, The main area where we are working is around 15ºN and 45ºW although day to day we are working in an area much larger around this-check out the map on the “about the cruise” page on the website.  Unfortunately we haven’t seen any sea monsters but we have seen dolphins and dorado fish (they are quite big!).  The sea has been calm so far and weather has been really good.  Hopefully there aren’t any submarines around because our instrument TOBI is being towed on a cable behind us and would be damaged or lost if it met a submarine!

Michelle


Q

Can you tell me what is meant by this: “Mid morning we crossed the Fifteeen-Twenty fracture zone” - What is a Fifteen -Twenty.........is that a size or # .........Can we see pictures of the ROCK.....Thank You for your time.

Mary, Arkansas

A

Hi Mary, The Fifteen-Twenty fracture zone is in the centre of our sampling area and is a trace on the seafloor of a previously active transform fault.  This is a fault where two tectonic plates slide past each other, once there is no more movement on the fault then the fault becomes a fracture zone and acts as a marker for previous plate motion.  Fifteen-Twenty refers to the latitude of this fracture zone. 

Michelle


Q

You often write about the "watch" in your diaries.  What do scientists watch for?

John, San Diego

A

Hi John, On our watches we are monitoring the ships position and all our instruments (water depth, gravity, magnetics) so that any changes can be observed as quickly as possible.  This allows us to have real time information about the sampling area.  When we are on station (stationary at a fixed position for e.g a drill site or the start of a dredge) then the watch keepers also monitor and record all the details of these events, having this information will make any future work on the samples much more useful as we will be able to say exactly where it came from and under what conditions it was retrieved.  At the moment the watches are also helping the TOBI pilots to track the ship position and TOBI’s position behind the ship so that TOBI remains above the seafloor and doesn’t crashes!

Michelle


Q

Does the wave motion of the ship vary the path of the sonar and if so, do you have software to correct for that effect. Thanks and good luck!

Scott Holmes, USA

A

YES IT DOES SCOTT. THE SONAR HAS A GYRO COMPASS AND FULL 3 AXIS ORIENTATION SENSO (HPR). IT IS ALOSO ABOUT 4 KM BEHIND OUR SHIP. WE USE THE HPR AND NAVIGATION DATA TO CORRECT THE PING RETURNS FROM THE SEAFLOOR. THE SONAR TRANSMITS A PING WITH A 0.25 DEGREE SPREADING ANGLE. THAT CAUSES THE BEAM TO SPREAD FROM A FEW METRES WIDE AT THE VEHICLKE TO A FEW TENS OF METRES AT 3 KM RANGE. WE CORRECT THE ECHO RETURNS FOR SPEED, PITCH, YAW, ROLL, HEAVE AND MOTION OF THE SONAR VEHICLE.

Bram


Q

Is the thickness of the upper mantle any different in this area than in other (with crust) areas? Enjoy this wonderful journey!

Alexandros Lioumbis, Greece

A

HI ALEXANDROS. I GUESS THE UPPER MANTLE MUST BE THICKER HERE AS IT IS EXPOSED ON THE SEAFLOOR RATHER THAN BEING 6-8 KM BELOW THE SEAFLOOR. THERE IS A DIFFERENCE BETWEEN CRUST (VOLCANIC IN THE OCEANS) AND MANTLE (PERIDOTITE) – BOTH THESE ARE GEOLOGICAL TERMS – AND LITHOSPHERE (BRITTLE MATERIAL FORMING THE OUTER SKIN OF THE SOLID EARTH) AND ASTHENOSPHERE (FORMING THE PLASTIC INNER PART OF THE SOLID EARTH) – WHICH ARE BOTH GEOPHYSICAL TERMS.

Bram


Q

Does this crust defect have any affect on gravitational data? Slight satellite deviations? And I am curious about magnetic deviations as well. This information is very exciting and we wish you all of the best weather.

Mark Fossati, Washington

A

YES MARK, THE HOLE IN THE CRUST MEANS THAT THE DENSER MATERIAL OF THE MANTLE IS BOUGHT TO A SHALLOWER POSITION THAN NORMAL. THIS CAUSES AN INCREASE IN THE EARTH’S GRAVITATIONAL FIELD AT THIS POINT. ONE RESULT OF THIS IS THAT THE SEA SURFACE GETS DEFLECTED UP AND OVER THE STRONGER GRAVITATIONAL FIELD. THIS CAN BE OBSERVED BY SATELLITES THAT USE LASERS TO MEASURE THEIR HEIGHT ABOVE THE SEA SURFACE, MAGNETICALLY, THE MANTLE MATERIAL ADOPTS QUITE A STRONG MAGNETIC INTENSITY AS THE MAIN MINERALS FORMING THE MANTLE (OLIVINE – AN IRON-MAGNESIU,M SILICATE)  REACTS WITH THE SEAWATER TO FORM SERPENTINITE (A LOW DENSITY MAGNESIU,M HYDROXY-SILICATE). A BY-PRODUCT OF THE REACTION IS AN IRON MINERALCALLED MAGNETITE. THE REACTION ALSO RELEASES HYDROGEN GAS THAT REACTS WITH THE SEAWATER CARBONATE TO FORM METHANE.

Bram


Q

Is there any evidence that magnetic reversals, as evidenced by seafloor spreading, have any bearing on climate changes. Have any studies been done to correlate changes in the earth's magnetic polarity, with changes to climate, ie ice ages?

Christine Beale, Oxfordshire

A

HI CHRISTINE, THE EVIDENCE FOR CLIMATIC EFFECTS CAUSED BY MAGNETIC REVERSALS IS RATHER SKETCHY – BUT IT IS GENERALLY THOUGHT THAT THE INCREASED INCEIDENCE OF SLOAR PARTICLES IMPACTING THE LOW-LATITUDE UPPER-ATOMOSPHERE HELPS NUCLEATE WATER DROPLETS CAUSING GREATER CLOUD COVER.

Bram


Q

Are the vacuum toilets working adequately?

Neil Mitchell, Manchester

A

HI NEIL, THE TOILETS DEVELOP A VERY HIGH VACUUM. IT IS RECCOMMENDED THAT YOU DON’T REMAIN SEATED WHEN ACTIVATING THE FLUSH. SHOULD ONE DO THIS, THEN THE NEAR PERFEFECT SEAL FORMED BETWEEN THE OCCUPANT’S POSTERIOR AND THE RIM OF THE BOWL WILL CAUSE THE OCCUPANT TO REMAIN ENTHRONED INDEFINITELY. DEFINITELY NOT TO BE ENCOURAGED.

Bram


Q

Even though you are drilling 1 meter deep in the mantle, is there a possibility of hitting a pocket of harmful gases while drilling?

Ashton & Gill, Woodstock, USA

A

HI ASHTON AND GILL, THIS IS A GOOD QUESTION.  I AM A MEMBER OF THE INTEGRATED OCEAN DRILLING PROGRAMME PANAL THAT TAKES CARE OF ENVIRONMENTAL AND SAFETY ASPECTS OF OUR DRILLING OPERATIONS. SHALLOW GAS IS A MAJOR HAZARD IN ANY DRILLING INTO THE EARTH AND MUST BE AVOIDED. HOWEVER, WITH OUR SHORT SAMPLING CORES, WE WILL NOT ENCLOUNTER ANY FREE GAS. ACTUALLY, THE MANTLE ROCK (PERIDOTITE) FORMS HYDROGEN WHEN IT REACTS WITH THE SEAWATER AND TNHIS IN TURN FORM METHANE WHEN IT REACTS WITH THE SEWATER CARBONATE. STRONG METHANE CONCENTRATIONS IN THE SEAWTER ARE AN INDICATION OF EXPOSED MANTLE ROCKS ALONG THE MID-ATLANTIC RIDGE.

Bram


Q

Lets say at one point, the mantle covered 100% of the earth's crust.  Aren't mountains made by the mantle pushing up into the air and another moving down.  Talking about plate tectonics.  So wouldn't your missing mantle be in the mountains?

Doc, Texas

After reading the previous questions and answers, I would like to commend you for your collective patience. My question is this: Are there any areas that are not under water that exhibit the same conditions, or is this type of event only found under the oceans? Also, what are the possible ramifications of your findings?

Mike Burns, Rhode Island

A

HELLO MIKE AND DOC. I’LLL TRY AND ANSWER YOUR QUESTIONS TOGETHER. MANTLE ROCKS LIKE THE ONES WE ARE EXPLORING AT THE MOMENT ARE EXPOSED ON LAND: IN CYPROS (THE TROODOS MOUNTAINS), AND THE OMAN. IT IS ALSOEXPOSED IN NEWFOUNDLAND. THESE EXPOSURES ARE IN THE FORM OF ANCIENT OCEAN CRUSTA AND MANTLE PUSHED UP INTO MOUNTASINS AND ERODED TO EXPOSE THE DEP-ROOTED ROCKS. HOWEVER, HERE IN THE MID-ATALANTIC RIDGE, THE MANTLE IS NOT PUSHED UP OR ERODED, AND IN FACT IS BEING ACTVELY EXPOSED, WITH THE FAULT TEAR GROWING CONTINUOUSLY.

Bram


Q

there have been 18 quakes on the mid-atlantic ridge since feb 1 2007 this is probably more than all last year.  all these quakes were about 10 km deep and all 5.0 give or take a couple of points.   these quakes go from off brazil to greenland sea and back.  what are you finding if anything relative to this movement
John Meller, USA

I am in 6th grade and go to Robert Millikan Junior High School in Sherman Oaks, California.  I wanted to wish good luck on your trip.  This is my question.   How have earthquakes shaped the area that you will be studying?  Are earthquakes responsible for the huge chunk that is missing from the ocean crust?
Aleq Quintanilla, California

A

HI ALEQ AND JOHN. UNUSALY FREQUENT EARTHQUAKE ACTIVITTY IN THIS AREA, WHERE THE MANTLE IS BEING EXPOSED AND THE CRUST TORN AWAY, IS ONE OF THE FEATURES THAT FIRST DREW THE SCIENTIFIC COMMUNITTY’S ATTENTION.

Bram


Q

I've read everything on the mission so far and I think that it's really cool with the sound velocity probe and everything!! Anyway, is it possible that these "crust absences" could start appearing in the other ocenas? If so, could this pose a major threat to humanity? Good Luck on you voyage!!

Kevin Kittinger, USA

A

YES KEVIN, THERE ARE OTHER AREAS IN OTHER OCEANS WHERE THE MANTLE IS BEING EXPOSED – THE SOUTHWEST INDIAN OCEAN AND THE GAKEL RIDGE IN THE ARCTIC ARE TWO THAT WE KNOW OF.

Bram


Q

In answers to several questions you point out that the warming effect of the thinner crust in the area concerned is very small but could it not vary considerably over time and in different locations and if the area is so large would not the overall effect of even a small difference be significant in maintaining ocean and atmospheric temperatures and over time contributing to changes? You accept the existence of continuous convective processes from the mantle through the oceans to the atmosphere but as far as I know it has never been properly quantified as part of the planetary heat budget in climate models.

Stephen, Cheshire, UK

A

HI STEPHEN, GEOTHERMAL HEAT INPUT FROM THE SEAFLOOR IS THOUGHT TO AFFECT OCEAN CIRCULATION. IA RECENT NUMERICAL MODEL  BY MAROVSKSA, INDICATED ABOUT A 40% INCREASE IN PACIFIC OCEAN CIRCULATION CAUSED BY GEOTHERMAL HEATING. BUT THESE ARE ONLY EARLY DAYS AND OUR UNDERSTANDING OF THE CONNECTION BETWEEN GEOTHERMAL HEATING (RELATED TO MANTLE CONVECTION AND OCEAN CIRCULATION) IS VERY SKETCHY.

Bram


Q

Do you think you will find some unknown micro-organisms inside the drilling samples ? Good luck everybody from Italy .
Marco Bazzolo, Padova, Italy

Wow! Thank You for sharing this experience on-line, it really means a lot to me...My question is: Do you think there will be any new form of species either plant or sea life due to this pheonomenon, it is a phenomenon right?
Susan Monkhouse, USA

A

HI MARCO AND SUSAN, THE HYHDROTHERMAL VENTS ARE KNOWN TO HOST EXOTIC MICRO-ORGANISMS. THE NOST UNUSUAL ARE THE ARCHIA, AN ANCIENT TYPE OF MICROBE THAT DATES BACK TO THE START OF LIFE ON EARTH. THESE ARCHIA ARE ALSO HYPERTHERMOPHIOLES AND CAN WITHSTAND UP TO 150 DEGREES CELCIUS AT 350 ATOMOSPHERES. WHERE HYDROTHERMAL VENTS OCCUR WITH MANTLE EXPOSURE, WE FIND A HUGE RANGE OF PRIMITIVE ORGANIC MOLECULES ARE FORMED BY INORGANIC REACTIONS – THESE REACTIONS FORM PEPTIDES AND AMINO ACIDS – THE BUILDING BLOCKS OF LIFE ITSELF!

Bram


Q

I've tried to google map your location as you travel with no success. Is there a way you can show us old folks  where you are on a google map and still make the students use the map coordinates to find you? I still maintain you will find the mother of a gouged out crust made by a planet collision during your trip. Be safe, be sucessul, be right.

Alex V., Canada

A

WE ARE CURRENTLY AT 15 DEGREES 04 MINUTES NORTH AND 13 DEGREES 25 MINUTES WEST. GOOGLE EARTH SHOWS THE SATELLITE ALTIMETRY DERIVED SHAPE OF THE SEA FLOOR (AFTER SANDWELL AND SMITH, 1997). IF YOU GO TO THIS LOCATION, YOU WILL SEE THE MID-ATLANTIC RIDGE (TRENDING NORTH TO SOUTH) AND EAST TO WEST TRENDING DEEP TROUGHS THAT ARE THE FRACTURE ZONES. ONE OF THESE IS THE 15-20 FZ – AT 15 DEGRESS 20 MINUTES NORTH.

Bram


Q

Would it be possible that all the environmental warm up can be traced back to this fact of the sea is exposed to the mantle? The warm up then carried to the poles and melting the ice caps?

Gene E. Sotory, USA

A

NO GENE. THE GLOBAL CLIMATE WARM-UP IS CAUSED BY THOSE OF US THAT BURN FOSSIL FUELS. AFTER ALL, THINK ABOUT THE FACT THAT COAL AND OIL IS MILLIONS OF YEAR’S WORETH OF STORED SUNLIGHT, AND WE ARE RELEASING ALL THAT ENERGY – AND ITS CO2 – BACK TO THE ATOMOSPHERE IN A FEW DECADES.

Bram


Q

i am a GCSE student from england and i just wondered if the hole could turn bigger and could you tell me what would happen if it did and why hasnt magma rised to fill up the hole when then plates separated?

Jason Wan, London

A

HI JASON, THE HOLE IS GETTING BIGGER, BUT RATHER SLOWLY BY BOUT 2-4CM PER YEAR). THE QUESTION WHY BASALT MAGMA HASN’T FILLED THE HOLE YET IS A GOOD ONE – AND ONE OF THE REASONS WE ARE HERE. WE’LL LET YOU KNOW WHEN WE FIND OUT.

Bram


Q

Do you think there is any chance that you will find any signs of life or even fossils in the mantle material?

Jim, Texas

A

NO JIM, THE MANTLE IS TOO HOT AND UNDER TOO MUCH PRESSURE.HOWEVER, WE MIGHT FIND NEW LIFE FORMS ON THE SEAFLOOR WHERE THE MANTLE IS NOW EXPOSED TO SEAWATER.

Bram


Q

What are the average ocean water temperatures that you will be encountering with this project from surface to where you will be working?

Pamela, North Carolina

A

HI PAMELA, THE SEA SURFACE TEMPERATURE HERE IN THE TROPICAL MID-ATLANTIC IS ABOUT 26 DEGREES CELCIUS. HOWEVER, AT THE BOTTOM, 400 METRES BELOW US, IT IS ONLY 2 DEGRESS CELCIUS. THERE ARE A COUPLE OF SITES NEARBY, ON THE SEAFLOR, WHERE THE SEAWATER IS HEATED GEOTHERMALLY BY THE HOT ROCKS NEAR THE SEAFLOOR. THIS WATER REACHES NEARLY 400 DEGRESS CELCIUS – ENOUGH TO MELT LEAD.

Bram


Q

How long has this 'hole' been in the ocean floor?  This press talks like it just popped up overnight and took everyone by surprise.

D. Taylor, Virginia

A

GOOD QUESTION D. GEOLOGICALLY THIS HOLE IS VERY YOUNG. A FEW THOUSANDS OF YEARS OLD. AND IT IS GETTING BIGGER EVERY YEAR – THE TEAR IN THE SEAFLOOR GROS BY ABOUT 3 CM. NOT MUCH, BUT OVER THOUSANDS OF YEARS IT ACCUMULATES. THE FACT THAT IT IS THE PRESS IS BECAUSE IT TOOK US ALL BY SURPRISE – WE DIDN’T THINK THIS COULD HAPPEN OUT HERE IN THE ATLANTIC.

Bram


Q

My understanding of the mid-Atlantic ridge is that it is an area where the American and European plates are separating.  This being the case I would assume fresh mantle material would constantly be welling up to the ocean floor to fill in the gap between the two plates.  Could you please explain the differences between normal oceanic crust, mantle material that is filling in the gap, and the material you are studying? Thank you, and I hope you have good luck and good health on your journey.  P.S. Enjoy your warm weather.  We did not get above freezing until yesterday.

Patrick Findling, Michigan

A

 OKAY PATRICK, THE MANTLE THAT WELS UP TO FILL THE GAP BETWEEN THE PLATES AS THEY DIVERGE DECOMPRESSES AND AS A RESULT IT MELT. THINK OF A BOTTLE OF SODA WATER. WHEN THE LID IS ON, IT IS JUST LIQUID WATER AND CO2 MIXED– ALBEIT UNDER PRESSURE. POP THE LID AND IT BOILS AS THE PRESSURE SUDDENLY DROPS. SAME HAPPENS TO THE SOLID MANTLE. IT GOES FROM SOLID TO PARTIALLY SOLID PLUS MELT. THE MELT FORMS THE VOLCANOES AND THE LAVAS THAT GENERATE THE CRUST. THE DIFFERENCE HERE IS THAT THE MANTLE ISN’T MELTING. WE DON’T KNOW WHY – WHICH IS WHY WE ARE HERE – BUT THINK IT MIGHT BE TO DO WITH WATER IN THE MANTLE…….. WATCH THIS SPACE.

Bram


Q

The area where the earth's crust seems to be missing....Could this be a remains of an underwater supervolcano?

Barbara Smith, Consett

 

A

NO - WE DON’T GET SUPER VOLCANOES ON MID-OCEAN RIDGE. THESE REQUIRE LARGE AMOUNTS OF WATER INJECTED IN TO THE MANTLE AND THIS TENDS TO ONLY HAPPEN ABOVE SUBDUCTION ZONES – WHICH ARE WHERE THE OCEAN CRUST IS CONSUMED BACK IN TO THE EARTH’S INTERIOR.

Bram


Q

Hi, basic question here:  Are the mantel and crust in the OCEAN very different from the mantel and crust of the (above-water) continents?  Have the underwater parts of the world always been underwater?  And the Above-water parts always above water (except for the continental shelf border)?   I don't understand why, as the new mantel is born (surfaces), why doesn't it send the above-water land underwater?  Is sea mantel/crust heavier or denser than continental mantel & crust?  Why do these above-water parts (pangea/continents) seem to just keep moving around but staying up?  Thanks!

Good luck with your project.

Vicki, Minnesota

A

THANKS VICKI FOR YOUR KIND WISHES, THEY ARE APPPRECIATED OUT HERE IN THE MIDDLE OF THE DEEP, DARK ATLANTIC OCEAN. YES, THE OCEANIC CRUST AND MANTLE ARE VERY DIFFERENT FROM CONTINENTAL CRUST AND MANTLE. THE OCEANIC CRUST IS YOUNG – LESS THAN 100 MILLION YEARS OLD. IT IS MADE OF BASALTIC MATERIAL, LAVAS AND GABBROS. THESE ARE MUCH DENSER THAN THE CONTINENTAL CRUST WHICH IS MADE UP OF LARGELY ALUMINOSILICATES AND QUARTZ. THE CONTINENTAL CRUST IS MUCH OLDER – UP TO 4 BILLION YEARS IN PLACES (4,000,000,000 YEARS). BOTH TYPES OF CRUST FLOAT ON THE MUCH DENSER MANTLE. THE HEAVY OCEANIC CRUST SITS MUCH LOWER THAN THE LIGHTER CONTINTAL CRUST. THE MANTLE BENEATH THE OCEANIC CRUST IS WARMER THAN  BENEATH THE CONTINENTAL CRUST, AND PROBABLY SLIGHTLY MORE MAGNESIUM RICH.

Bram


Q

First of all good luck to all of you. Do you think that this kind of fracture in the bottom of the ocean can jeopardize the sea life? and do you think that the magma can come out and this would be catastrophic to the planet?.

Geraldo Santos, Brazil

A

Hi Geraldo – The fracture won’t jeopardise sea life because the life down on the ocean ridges is specially adapted to its environment. As well as large sea life like crabs, there are bacteria that live in ocean vents that are adapted to live in environments where the water is very hot and loaded with chemicals like sulphur.

The exposed mantle at the ocean floor is not molten, but solid. There are, of course, many eruptions at the mid-ocean ridges happening all the time– these are what form the normal crust. This region of exposed mantle is simply part of the plate tectonic cycle that we have yet to fully understand, rather than an abnormality that could be dangerous.

SAM


Q

I would just like to say that what you're doing sounds fascinating. I happened to see a headline on Yahoo!'s homepage, and it was about your team. I think it's really fascinating that a tectonic plate is missing from the bottom of the sea. This is an awesome discovery, and you're exactly right. It does kind of present an argument as to how we all think Earth evolves. I wish you the best of luck, and I am also going to tell some of the geology teachers at my school about your team, and this website.

Best Wishes,

Logan.

P.s. I’m 16, and I’m a sophomore in high school. (10th Grade) also, I’m thankful that you update your latest news on the calendar page. The information is fun to read.

 

A

Hi Logan- Please do let other people know about our website – we’d love your classmates to be able to follow us too! Glad you’re enjoying watching our cruise!

SAM


Q

If we ever have a strong enough material to survive magma, would this break in the crust be an ideal place to "journey" into the Earth?

Derek McDowell, Aged 13, Indiana

A

Hello Derek- what a great question! I suppose in theory yes, in that we could get straight to the mantle without going through the crust- I guess you could try to do this through the magma chambers of volcanoes too! Unfortunately if you tried to travel to the centre of the earth it wouldn’t just be tremendous temperatures you had to deal with, but massive pressures too that would crush a probe or vehicle. And don’t forget, the core is made of molten metal, we haven’t invented/ discovered anything that could survive these conditions yet!

SAM


Q

What evidence do you have that the area you intend to study is actually mantle?  Is it likely that other such regions exist elsewhere, or is this probably a one-of-a-kind geologic feature?  Thanks in advance for your response.

Jeff Wolinski, Grove City, USA

A

 Hello Jeff- Yes, there are other regions like this elsewhere on some of the mid-ocean ridges. We use sonar to image the seafloor, and some of the features we see here in our study area look very much like those in other areas that have been sampled and have been found to have exposed mantle rocks on them. As to whether there actually ARE mantle rocks exposed here in the way we suspect, we will have to await the results of our sampling to find out for sure!

SAM


Q

Extremely curious about exposure of mantle in Atlantic.  Is the sea-water exposed mantle stronger than crust?  Can you gauge the thickness of the hardened mantle?  Is there a risk of rupturing?  My uneducated guess would be that the weakest points would be around the rim where crust meets mantle.  Have a million more questions, so I'll be checking this site regularly to see if others have questions similar to mine.

Good luck on your science and I look forward to your publications.

Brent Halling, Houston

A

Hi Brent- Thanks for your questions. When mantle rocks are exposed to seawater, they become altered, with much of the original olivine that makes them up changing to a very soft, soapy-feeling mineral called serpentine. When this happens the rocks become a lot softer, and less strong, but this alteration only extends to where water can reach to assist in the alteration reactions.

Gauging the thickness of layers under the earth’s surface is difficult – we use geophysics to image density changes as sound waves pass through from one compositional layer to another.

The area of exposed mantle we are investigating cannot ‘rupture’ in a catastrophic way, causing lots of magma to be released. There are volcanic eruptions taking place on the seafloor all the time – these are what create the normal oceanic crust – but the amount of magma that can erupt in any one go is controlled, because there aren’t large quantities of molten rock sitting beneath the ridge, only very small amounts of melt are extracted at any one time, as plate separation causes the mantle beneath to melt due to decompression.

SAM


Q

How exactly did this "Hole" get discovered??? Satellite? And is there cause for concern? I don't suspect you'd answer yes. Do you have hopes of probing deeper into the earth??? Thanks for your time!!!

Cole Neuman, British Columbia

A

Hi Cole – At other ocean ridge sites where mantle rocks have been found, there are particular shapes that show up on bathymetry (seafloor topography) maps. Scientists noticed that the same shapes are seen in this region of the Mid-Atlantic ridge, and so we decided to investigate to see whether mantle rocks were exposed here also.

We don’t understand the ‘missing crust’ very well yet, but it is just a part of plate tectonic theory we have yet to pin down. This anomalous area of spreading ridge is a natural phenomenon, which poses no risk to the environment or to man- but it does provide us with an interesting glimpse inside the Earth!

About probing deeper into the Earth – there are drilling ships that can drill cores much deeper than we can – we only drill for one metre just to test what sort of rocks we can see on the surface – however, it is technologically very difficult to drill very far, and even if we could drill deeper, soon very high temperatures and pressures would prevent us going any further.

SAM


Q

Dear Staff,

What if any are the risks in drilling so close to the mantle?  Do we have any understanding on the mantle composition beyond our present knowledge?  As a follow up, how long will it take your crew to get to the bottom to begin the collection process?  Thank you and good luck!  God bless and stay safe!

Rick Sprinkle, Ohio

A

Hello Rick – The kind of drilling we are doing is in no way dangerous – we’re only drilling the top metre of rock to test its composition. There’s no molten material below where we are drilling, in fact, there’s very little molten material in the mantle at all – most of it is solid until it becomes decompressed at the ridge. We’re hoping that if we find the samples we need we’ll be able to understand a bit more about why the crust is very sparse here. It took us just about a week to get to our sampling station. Now that we’re here, it takes about 2-3 hours to deploy an instrument to the seafloor because it’s such a long way down (nearly 5km in places!).

SAM


Q

Since I can't conceive of an area this size all-bubbling up with lava, there must be sections that are quiet. What is the difference between crust and mantle? Or in other words, how do you tell that this area is mantle and that is crust?

Glenn Jorgenson, Sacramento

A

Hi Glenn – Yes, you’re right, the exposed mantle that we are investigating is all solid, not molten. In fact, very little of the mantle is molten – it only melts beneath the ridge axis, and even then only a tiny amount of it melts at any one time. It melts because as the ridge plates move apart, it decompresses. The mantle rocks we are looking at are made up of the material that is left over once melt has been extracted, whereas the crust is made of the basalt that cools from the melt. The rocks are related, but due to the fact that the melt comes out of the mantle, taking some elements with it but leaving others behind, they have different chemistry.

SAM

Q

First off, I wish all of you the best of luck on your scientific journey into the Mid-Atlantic.  Hopefully you encounter nothing but smooth sailing, and clear skies. As for my question....  Are there any leading theories as to why the earth's crust is missing?   

Joe Ferrell, USA

A

Hi Joe! At the moment scientists think that the crust is missing because the crust near the ridge is cut up by large faults that stretch and snap the crust away and exposing the mantle underneath.

SAM


Q

Dear scientists,

First off: Good luck on your mission. I was very surprised to hear about this gap in the middle of the ocean. I hope you can fix it soon. I have a question or 2:

1. Does the water not cool down the magma that is exposed and so create a crust?
2. Have you found any large underground caverns or entrances to an underworld or 'hollow earth'-alike paradise?
3. How did this happen? Is it a natural cause or could this be the result of some past event? (meteor impact, earthquake, polar shift?)
I hope you have the time to answer my questions. About question nr. 2: I know it's a ridiculus notion in the scientific world, but you can never know for sure.

Kind regards,

Richard Vrielink, Netherlands

A

Hello Richard – The exposed mantle that we are investigating is in fact solid – it wouldn’t be possible for molten rock to sit long at the surface without cooling in the seawater – in fact, lavas often cool so fast on the outside that they quench to volcanic glass because crystals don’t have time to grow.

There are sometimes lava tubes /bubbles on the ocean floor that are hollow, but these often cave in and don’t lead anywhere in particular. The conditions down at the seafloor mean it isn’t possible for humans to explore there – the pressures are exceptionally high and only animals adapted to live in such harsh environments can survive.

As for why the ‘hole’ in the crust is there – it wasn’t caused by a catastrophic event such as an impact because it’s not a crater, rather it’s a place where the crust is so thin and sparse that the mantle beneath it is showing through. We suspect that the mantle is exposed by a particular type of fault action, but we are still investigating this.

SAM


Q

Since most things have a mirror image going for them could there be another area opposite this on the other side of the planet? Could this be an indicator to the extent of the current polar shifts state? You will be checking the extent of magnetic and electrical fields? If this is a key stone area then is it a good idea to drill considering the pressure that could be released should a crack developed from the drill point? Will the drilled area be put under constant monitoring to see what happens after drilling if drilling goes ahead?

Only have to look at Io to get an idea of what we don't want to happen here.

Please be careful.

Bill, Chicago

A

Hi Bill – Not sure about the mirror image theory – I think that the development of these mid-ocean ridge areas with sparse crust is likely to be a result of local tectonics and mantle heterogeneity. The polarity of the Earth’s magnetic field is recorded in mid-ocean ridge basalts by alignment of iron-bearing crystals (magnetite), but ridges see many magnetic reversals as they develop, and they still have the same tectonic features. We are recording magnetic fields so that the geophysicists onboard can reconstruct the original orientation of the rocks when they formed. We’re also recording gravity fields because these change for areas with different density and allow us to interpret the environment beneath us.

Regarding drilling, the drill we are using only penetrates the seafloor to a depth of one metre to collect samples of the rocks at the drill site. There is no molten mantle material where we are drilling, and even if we were drilling deeper there would be no risk of triggering volcanic activity etc.

SAM


Q

Hello All!

I would first like to say that you all are doing a terrific scientific job and kudos to all! Being that the crust is not present, does the weight of the ocean directly on the mantel cause unforeseen shifts or rather events not normally seen where the Earth is intact?

Roy Fernandez, Texas

A

Hello Roy! The rocks that we are investigating experience HUGE forces due to the action of plate tectonics upon them, and it is this action that governs earthquake activity, controlling the way that the rocks shift relative to each other. Faulting has a major part to play in the way that mid-ocean ridges develop, and these forces are substantially greater than any compressive force exerted by the water column. 

SAM


Q

Could the entire mantle eventually be exposed, and if so, what would that mean?

Ashley Paige, Woodstock, USA

A

Hi Ashley. The mid-ocean ridges are constantly producing more crust as the mantle melts and wells up between the plates to ‘fill in the gap’. This process is taking place all over the world, has been for a long time and will for a very long time into the future. These ‘missing crust’ sections must have been around on the ocean floor for a very long time too, it’s just that we have only noticed them recently – after all, we have only ever explored a tiny percentage of the seafloor because it is so vast. This isn’t a new tectonic phenomena, it’s just one that we don’t understand yet.

The production of the Earth’s crust could only ever stop if plate tectonics stopped working, and this can only theoretically happen if the Earth’s core goes cold and stops moving. I don’t think we need to worry about this for a few billion years!

SAM


Q

How are the core samples going to help you find out where the crust is? When you find out what caused this piece of crust to not be there, could this affect the future now or in the future?

Brittany, Woodstock, USA

A

Hi Brittany! When we examine the core samples in our labs we will be able to look at their chemistry and the minerals and structures they contain, and this will hopefully tell us about why the mantle is exposed on the ocean floor. We are trying to form models to describe why in some places the mantle produces less melt and so we get thin crust or no crust at all. Chemical studies should tell us about the mantle beneath the seafloor here and show us if it is unusual in any way, and studies of structures will tell us about how faulting and tectonics reveals the mantle on the seafloor. The ‘missing crust’ is just a normal part of the planet’s plate tectonic system, and so it poses no danger to the environment.

SAM


Q

Why is the mantle that is exposed rock and not magma?

Summer, age 15, Florida

A

Hi Summer – great question! One thing that most people don’t realise about the mantle below our crust is that it is actually mostly solid. There are small pockets of magma that melt from the mantle in specific places, like beneath volcanoes and at the middle of the mid-ocean ridges. This mantle melts because as the tectonic plates separate, it goes from being at very high pressure to much lower pressure, and this causes it to change from solid to liquid. This only ever happens to a small bit of the mantle at a time, so the rest of the mantle is solid rock, like the bit that we are studying at the moment.

SAM


Q

Good Luck! I have a few questions: 1) How hard is it to break down the core samples? 2) How will this help you to determine exactly where the crust went?

Brittany Crowe, Virginia

A

 

When we examine rocks, we can do it in several ways. One is by eye, so we look at the samples and describe the minerals and structures we can see. We can also cut the rocks down to very thin slices (so thin you can see light through them!) and mount them on slides to look at under normal microscopes and more powerful electron microscopes called SEMs. With these we can see a lot more of the minerals and the way they are distributed than we can by eye. When we want to test the chemistry of the rocks we can dissolve them in powerful acid in the chemistry labs and send the dissolved rocks into spectrometers. The chemistry of the rocks and the minerals they contain tell us about the original mantle that they formed from, and structural studies can tell us about faulting that the rocks have experienced since they formed. We can put all of this evidence together to build up a picture of the rock history that will hopefully allow us to build a model of why the crust isn’t formed normally in these areas. 

SAM


Q

Do you believe it is possible that other "intelligent" life forms exist below the ocean, but not in outer space?

Bryan Ingham, Woodstock

A

Hi Bryan – I guess this is one of those questions that science just can’t really answer yet. We still don’t know a great deal about everything that lives in the oceans because they are so vast we have most of it yet to explore. There are many creatures that can live under the kind of conditions we find at great depths in the ocean, even bacteria that can live on volcanic vents, so I’m sure there are many new species yet to discover. As to there being ‘intelligent’ life forms – it seems unlikely. In outer space, who can say? Many scientists believe that it would be possible for life to exist beneath the frozen oceans of Europa, as similar environments here on Earth (sealed lakes in Antarctica) do host whole communities of life. We’ll just have to wait and see!

SAM


Q

How can you take pictures in trenches that are really deep in the ocean, when I thought the light on the camera doesn’t show objects that are far away? How do you know what your looking for, you’re in the dark. How far does the camera work until you can't take pictures?

Amanda and Neoma, Woodstock

A

Hi Amanda and Neoma! This is a brilliant question! When we take ‘pictures’ of the seafloor, we don’t necessarily mean that we’re using cameras. We can use cameras linked to the ship on long fibre-optic cables to take pictures of the site where an instrument such as our rock drill lands, but you’re right, beyond the limit of the drill’s light, we can’t see anything.

This is where sonar comes in. TOBI (see pictures in our diary) is like a giant loudspeaker that broadcasts sound to the seafloor. Lots of the sound is reflected away, or absorbed by the seafloor, but some is backscattered back to TOBI. TOBI records these returns and uses them to build a picture of the seafloor, which we can see as an image that looks like a photograph. TOBI works well at about 400m above the seafloor, but can only operate to 1000m above the seafloor before it can’t receive the signals and so we lose our picture.

SAM


Q

This mere fact that the mantle is exposed is intriguing enough, but the sheer width is quiet startling.  My question is wouldn't the pressure and temperature of the water force the exposed area to reform into a new section of crust?  I am not a geology major so forgive my confusion.

Dylan

A

Hello Dylan – The area of exposed mantle is solid rock – you’re right – an area of molten rock at the sea surface would very quickly cool and become solid. It’s actually the TYPE of rock that defines this area as mantle material rather than crust. The crust is made up of basalts that melt out of the mantle, so although the crust forms from the mantle and is related to it, it has different chemistry.

SAM


Q

Have you run across any minerals of importance during your search and drilling?  Since the tectonic plates are always in motion, is it possible that you may detect oil or other valuable commodity?

Roland, Florida

A

Hi Roland – The type of rocks we are looking at don’t contain oil. Oil is formed from organisms, so the source rocks for oil have to be sediments with a non-porous cap rock over the top of them to keep the oil in. The rocks we are examining are all igneous. There are no minerals that can be mined from the ridge due to its great depth and inaccessibility – however, ‘black smoker’ vents at mid ocean ridges DO concentrate minerals like copper, and long after these ridges have stopped working some of them get lifted up on land by tectonic processes. This gives us access to the ancient mineral deposits they formed, and we do mine these around the world.

SAM


Q

Would it be possible that all the environmental warm up can be traced back to this fact of the sea is exposed to the mantle? The warm up then carried to the poles and melt the ice caps?

Gene E. Sotory, USA

A

Hello Gene – The mantle rocks that we are examining are actually solid and cold. When normal volcanic activity takes place at the ridge it does generate heat, which does warm the water. However, in comparison to the temperature control by the global sea currents, the ridges have a negligible effect.

SAM


Q

I am fascinated by your project of figuring out how and why the earth's mantle is exposed...My father was a geophysicist and did research back the late fifties at Boston College. Before the idea of plate tectonics was proved.  I was in an honours geology course with Tracy Atwater at UCSB in 98...love this stuff. My question: when you all say "dark green rock", can you be more specific?  It is obsidian-like silica based or what exactly?  Maybe this is what you are finding out...thanks for this incredible opportunity to monitor your fascinating expedition!

Allya Peerzada, Pasedena

A

Hi Allya – I guess you’re referring to an earlier description of the mantle rocks we’re looking for. The rocks generally have a green colour to them because they have been altered by interaction with seawater, which replaces a lot of the original olivine crystals with a soapy, soft mineral called serpentine. The mantle rocks are mostly olivine-rich, though some also contain pyroxene and iron oxides amongst other things.

Obsidian glass forms when lava erupts into cold seawater and cools so rapidly that crystals don’t have a chance to develop. These glasses are found as rims on basalts, so are part of the crust, not the mantle.

SAM


Q

Do you bring your own supply of fresh water on your trip or do you desalinate the ocean water? Do you have a chef or cook or do you all take turns cooking, and what is a typical meal for the staff? What is the weather expected to be like in the drilling area for the time you are there?

The Mitchell Family, Wisconsin

A

Hello to the Mitchell Family! We desalinate our own water on board, as well as carrying a supply of fresh water in the stores. We have wonderful galley staff that prepare three meals a day. There aren’t really typical meals; we have everything from roast dinners to curry or Chinese – and we get dessert too! We have plenty of fresh fruit and salads to keep us healthy when we’re working as well.

The weather is expected to be pretty good. At the moment the seas are very calm, the sun is shining and it’s 27 Celsius. Some of the scientists are even taking time out to sunbathe when they’re off duty!

SAM


Q

I am greatly interested in science, (Particularly Marine Biology), and I was wondering, if the edge of the indention in the crust is like a cliff (steep), or does it slope?

Lauren Cook, USA

A

Hi Lauren – I guess you mean the shape of the area where the crust is missing. Actually the areas that we suspect contain mantle rocks are domed upwards so they are topographically higher than the surrounding areas where the crust survives. This doming is part of a complicated series of tectonic processes that we don’t quite understand yet- this is part of what we are studying right now!

SAM


Q

Question for Sam; How do you want your frozen fish fingers cooked?

Galley Staff, RRS James Cook

A

Gently grilled with a slice of fresh lemon and a side salad please. Oh, and a bit of Choccie ice-cream for afters…

SAM


Q

On the eastern seaboard of the U.S. we are fearful of tsunamis caused by undersea earthquakes. Because this side of the of the Atlantic Rift is old and brittle, as the ocean rises and creates more pressure on the rift could this make quakes along the rift and its fault lines have a reduced or an increased impact on intensities of quakes?

Lloyd Hart, Canada

A

Hi Lloyd – All places where tectonic plates meet have high instances of earthquakes, and there have been a lot of small earthquakes recorded around the ‘missing crust’ regions that are associated with faults developing near the ridge axis. To create a Tsunami though, you need a very large vertical offset on a quite laterally extensive fault, or possibly for a large amount of land to fall into the sea, for instance if there is a major slope failure on an island. High instances of low-magnitude earthquake activity in areas such as this are normal, and don’t represent an increased Tsunami risk.

SAM


Q

How would you advance in science by taking samples of the mantle??

Cassidy Hamilton, Woodstock, USA

A

Hi Cassidy. By taking samples of the mantle rocks we can examine their chemistry and structural features. This tells us about the chemical fingerprint of the mantle in this area, and about the tectonic forces and alteration that the rocks have experienced in their lifetime. This allows us to build up a bigger picture of the kind of environment that the rocks are forming in, and with these observations we can inform and improve our models of how tectonics operates on the seafloor.

SAM


Q

Does the wound in the crust affect any of the plants or animals on the ocean floor? If not why?

Adam Shillingburg, Virginia

A

Hi Adam. The creatures and bacteria that live at these depths on the ocean floor are highly adapted to the environment in which they live. They live without light, and some have adapted to survive in the very hot water that is ejected from volcanic vents, and feed on the chemicals that are erupted there. The exposed mantle areas here don’t really change this environment for them, and so they can survive well.

SAM


Q

How does the micro study obtained from drilling shallow samples help you to understand the macro elements of plate tectonics?

Kurt Kruse, Iowa

A

Hi Kurt – we look at two distinct things here. Firstly we can examine the mineralogy and chemistry of the rock samples we collect, and this allows us to ‘fingerprint’ the mantle, working out whether it has chemical influences from heterogeneous spots. We also carry out structural studies of fabric in the rocks, and this allows us to reconstruct the tectonic forces that the rocks have experienced throughout their lifetime. When we put all this information together it allows us to refine our models of how plate tectonics works on a macro scale.

SAM


Q

Hello! We are discussing your cruise in my GCSE geography class and I was wondering: Why hasn't a new oceanic crust been formed? Is the mantle completely exposed? Wouldn't the ocean temperature rise? Thank you.

Marwa, London

A

Hi Marwa! Great that your Geography class is following our work – say hi to them all from the science crew!

The mantle is only partially exposed. In some areas it is covered by thin areas of normal crust. What normally happens at the mid-ocean ridges is that some of the mantle melts along the ridge as the tectonic plates move apart, and the melt moves in to fill the gap. At our study area, the plates are stretching apart, but sometimes instead of melt filling the gap, we think that the plates are stretching and faulting, so that the existing crust gets split apart and we see the mantle below it. The mantle rocks that we are looking at are solid and cold so they don’t heat the seawater. The molten lava erupted along the centre of the ridge does heat the water, but this heating effect is insignificant when compared to the temperature effects of the ocean currents.

SAM


Q

I think there is enough evidence to conclude that the Earth has experienced a few cataclysms in its history. Could this area be the result of a meteor? Either the peridotites are from the meteor itself or a result of the meteor impact bringing forth mantle rock? I don't know how much volcanic activity that area contains but maybe the scar never healed. I wish all of you the best and am looking forward to further updates. Thank you.

David Barstis, Connecticut

A

Hello David – We think it’s quite clear that this ‘missing crust’ area formed as a result of plate tectonic action. There is a lot of evidence to support a model where the mantle beneath the crust is exposed by a particular style of faulting.

Meteor impacts generally leave quite round craters with evidence of melting of both terrestrial rock and meteor material. There are also some giveaway signs such as fracturing inside quartz crystals from the impact, and unusual element concentrations and isotope ratios, which we don’t normally find on Earth. If we were looking at a crater here I think we would be seeing a much rounder feature with evidence of sediment melting on impact. In fact, were this an impact crater, I don’t think we’d see it all because it is likely that by now it would have filled in with marine sediment. These areas are elevated and don’t have the correct topography, morphology or geochemistry to support a meteor impact theory.

SAM


Q

Hi guys. Your venture sounds fascinating. Will you be studying the wildlife down there also, or just the geology? If this has been in existence for some time there could be some interesting "beasties" adapted to the area. Best of luck and a safe return for all.

Lissa Fisher, Brisbane, Australia

A

Hi Lissa – on our cruise we’re focusing on the geology – there aren’t any biologists onboard or any plans to sample biology. These areas of exposed mantle are close to the axis of the Mid-Atlantic Ridge and aren’t a significantly different environment that the biology should differ from normal. There are some quite fascinating beasties down there though, like extremophile bacteria that live on ocean vents, and crabs and shrimp that have evolved to live in complete darkness.

SAM


Q

How did each of you on the team luck into being picked to do this exciting project?  Did Roger choose who would make the trip with him, or is there a higher power at work?  I would think such a mission would require a quite sizeable amount of funding...who is behind the scene on that?  Are there any plans already in the works for future ventures?  Michelle, I look forward to your diary entries every day, and Chris, I like your picture the best.  All of you stay safe out there, and keep the info coming. 

Bo Harris, Houston

A

Hello Bo.  I initially had the idea of using the TOBI deep-tow to map out the areas of peridotite – mantle rock – that  people had been finding by dredging (that is, dragging a bucket over the sea floor!)  I knew Chris MacLeod had done some previous work in this area, so I contacted him, and I also contacted Bram for his expertise in chemically analysing rocks (I had known all three of them for many years, and worked with them before).  We three then wrote a proposal to the British Natural Environment Research Council – similar to your National Science Foundation) to request funding for it. They send it out to other scientific experts  - a process we call “Peer Review” to comment on the innovation, quality and feasibility of the proposed work.  That was in 2002.  We did not succeed at first (there is strong competition and success rates are about 20%), but revised and resubmitted the proposal, and finally funding was agreed in 2004.  We then entered a queue waiting for ship time, which was finally announced in 2006!  So it is quite a process.   Yes, we do have plans for future ventures.  Bram and I will be studying another part of the Mid-Atlantic Ridge probably next year, and we all have proposals at varying stages in the system. 

Roger

Hi Bo, I’m glad you are enjoying the diaries! I hope you enjoy our little interviews of the crew! Michelle


Q

Roger noted in a previous answer: “What is unusual about the area we are going to is that it appears to be a large area of missing crust, and it looks as though the crust was never formed there in the first place.”

Could you provide more detail as to why this may have been the case. If one goes back to about 250 million yeas ago, wasn’t this area all part of the Gondwanda landmass prior to the North/South America and Europe/Africa split?

Hope the weather has been kind to you and the equipment free of gremlins!!

Todd, Ohio

A

Dear Todd,

It’s important to understand the difference between oceanic and continental crust and the “lithosphere”.  Basically, the lithosphere is the rigid, outer shell of the Earth, and varies in thickness from just a few kilometres under mid-ocean ridge axes to perhaps 300 km under very old continents.  The crust is the upper part of the lithosphere.  Under the oceans, it is mostly about 6 km thick just made up of volcanic material.  It is continuously created at mid-ocean ridges as the lithospheric plates separate, and gets subducted back into the mantle at subduction zones (oceanic trenches), in a cycle lasting 200 million years or so.  On the continents, the crust is more complicated, and consists of ancient recycled sediments as well as volcanic and other material, and is considerably thicker – about 30 km on average. This means that continental crust and lithosphere are more buoyant, and can’t be easily subducted, so once formed they stay on the surface of the Earth.  So when Gondwana split, the continental crust did indeed remain on the surface, but new ocean crust has been forming in the gaps ever since.  Sorry if that’s a little complicated, but I hope it answers your question.  And yes, the weather has been fine, and we have not had too many gremlins!

Roger


Q

Dear Sir(s),

I am a student of Prof. Dr. Victor Jetten and Dr. C.J. van Westen of ITC and is a friend of Prof. Peter Atkins and Dr. Daniel Donegue, Department of Geography, University of Durham. I am basically from Kerala, India. I wish you a happy journey and do expect your voyage to make significant contributions to the understanding of the earth. I was curious to know the implications of this find (of missing crust) on the continental drift theory?

Sekhar Lukose Kuriakose, Netherlands

A

Dear Sekhar,

Thank you for your interest in our work!  I think the implications for plate tectoinic theory are that we are looking at a new way of forming the oceanic lithosphere.  Classical plate tectonics views the ocean crust and lithosphere as being formed mainly by injection of magma at mid-ocean ridge axes, with about 10% - 20% additional stretching on brittle faults.  Here, our preliminary results suggest that there is less magmatic input, and that in some places the mantle comes directly up to the seafloor along large, long-lived faults that may remain active for millions of years.

Roger


Q

Hi what is the spreading rate at this part of the mid-atlantic ridge? Correlates this hole with an 'ultraslow-spreading ridge'?

Brigitte, Switzerland

A

Hi Brigitte,

The full spreading rate here (i.e. the separation rate between the two plates) is 25 km per million years, which is slow, though not “ultra-slow”.  Although spreading rate is certainly a major control on the style of seafloor spreading, we think there are other factors such as mantle temperature and composition (ease of melting) that probably play a part.

Roger


Q

Looking at the size of yur ship I was wondering how many ships crew does it take manage the RRS James Cook ?

Chris Greer, Maryland

A

Hi Chris,

James Cook has a total complement of 40:  Captain, 3 bridge officers, 3 engineering officers, 1 electrician, 1 deck officer, 4 petty officers, 4 seamen, 1 purser, 2 cooks, 1 steward, 1 catering assistant, 4 scientific support staff, 2 TOBI engineers, 4 drilling engineers, and 8 scientists!

Roger


Q

Congratulations on getting down 2000m ! There doesn't appear to be as much silt as what I expected to see. Is this the picture, turbulence from the rock drill? Any current at those depths, sea life?  I was also wondering about the relief in the area, pretty much flat, rolling mounds or? Lastly will ya'll be checking out the edges of the FTFZ,is it abrupt or gradual?  Ya'll are great thanks for taking us on your expedition, through your eyes we are there too!

Tony, Texas

A

Hi Tony,

We actually have to try quite hard to find places where there is not too much silt, since the drill will only penetrate about a metre.  We did a preliminary depth survey, and chose a point just on the lip of a cliff, where we hoped there would not be too much silt but also it would not be too steep to drill.  We then spent a couple of hours moving the drill very slowly over the bottom while watching its video camera for rock outcrops (first view was just sediment).  The first one we tried was too steep and the drill fell over, but the second time we succeeded!

Roger


Q

From what I understand, this area in the Atlantic is not as deep as the Marianas Trench in the Pacific. How then is it possible that the mantle is exposed in your area and not in the deepest part of the oceans? Or is it?

By the way, I think it is great you are allowing us layfolk to field questions. The media coverage of this is often confusing and inconsistent, but your site answered allot of my questions and is greatly informative. Thank you.

Greg Kemper, Italy

A

Dear Greg,

Glad you are finding the web site useful!  To answer your question: the tectonic plates comprise the outer, rigid shell of the Earth, and (usually) consist of both the crust and the very uppermost mantle.  The absolute depth of the plates depends on the forces acting on them: at mid-ocean ridges there is hot mantle underneath and the plates themselves are hot, so they expand thermally and are buoyed up.  At trenches, the plates are old and cold, having shed their heat to the seawater, and they are being dragged down by the weight of the subducted part (already going down into the mantle).  But because the plates themselves contain part of the mantle, it can potentially be found anywhere below the seafloor just below the base of the crust.  Because some of the crust (made of volcanic rocks) is missing here, we see the mantle directly.

Roger


Q

It is very interesting what you are doing. I wish you all kind of success for which it will be positive for the deeper knowledge of our seas and earth. Question: Apart of you, as scientifics, are there other crew members like Captain, engeeniers, mates, sailors, etc or, do you manage the entire operations needed onboard and navigation?

Pedro, Bilbao

A

Dear Pedro, Thanks for your good wishes. James Cook has a total complement of 40:  Captain, 3 bridge officers, 3 engineering officers, 1 electrician, 1 deck officer, 4 petty officers, 4 seamen, 1 purser, 2 cooks, 1 steward, 1 catering assistant, 4 scientific support staff, 2 TOBI engineers, 4 drilling engineers, and 8 scientists!  As scientists, we are very dependent on the skills and dedication of all the ship’s crew to support us, and we are very grateful to them.

Roger


Q

This is for Davie and Iain.  I worked as a driller exploring for minerals such as gold and asbestos (dry drilling) in western North and South America, and I also ran an oil rig in the western US.  I have core drilled, and used compressed air and mud.  I am now a history professor working in the field of environmental history. I wanted to give you my background as a preface to my questions so that you could talk technically while answering my question(S) which is (are): what type of equipment do you use to approach the exposed core?  Are temperatures and the composition of the landing surface (if you have to set down upon the exposed core) a factor in your work, and if so, how do you address those factors?  If you take a core, how is is handled afterwards (collected, stored)? How do pressures at such depth force you to modify you equipment and your proceedures?  Finally, what is your power plant?  Diesel? Nuclear? and how long can you run? One of my students wanted to know if you could calculate the environmental impact of your expedition upon the ocean floor?  She meant, I presume, the cost/benefit ratio of your expedition.  Thank you so much for your time and patience with our questions.

Richard Adkins

A

Hi Richard

I will try and answer what you have written but I am unsure on some of the points you have mentioned. The British Geological Survey Operate a number of remote seabed rockdrills, all of witch have been developed in house by our team of engineers in the Marine Operations Dept Loanhead in Scotland. We currently run three different rockdrills that can recover different lengths of core in different conditions.

The drill we have onboard is our smallest drill that weights just under one tonne and is constructed from stainless steel. This drill is powered solely by electricity that is sent down an umbilical cable to the drill. This power is then fed through a transformer to give us the correct voltages subsea. The drill is controlled by means of a computer at the surface that also transmits its information down the umbilical to a subsea computer that then controls the drilling operations.

Our other larger drills that can recover up to 15meters of core in water depths of 3000m are again fed with electrical power from the surface. The difference with these is that the power then feeds an electrical motor that in turn runs a hydraulic pump. This give us much more power subsea to deal with higher torques that are required to cut deeper core samples.

As for pressure you are correct in stating that this is a problem. The main subsea computer and the camera system we have onboard are both contained within pressure vessels. These have a depth rating of 5000m. The other items on the drill such as the transformer, gearboxes and motors are all pressure compensated. This is done by having an oil filled reservoir with a rubber bag inside. When the drill is then lowered to depth, the bag is then squashed by the external pressure thus increasing the internal oil pressure to the same as the ambient pressure.

Temperature is an issue if you are near black smokers as they can reach very high temps but normally the biggest issue with temperature is the cold especially if you are working in a hot climate. As the subsea temperature can be greatly different from that on the deck temp on the vessel. This can induce stresses with in the drill structure and can cause fractures if the drill is lowered to the seabed to fast. One other point on temperature is the temperature of the drill bit. We use a small pump on the drill to circulate seawater through the drill barrel to cool the bit. You mentioned mud in you email. This is often used on larger drill ships but we do not use it on the small seabed drills, as the pressures to lift cutting are not as great. This also has less environmental impact.

On core handling. When the drill is recovered to the surface the drill barrel is removed. The drill bit is then taken off and the inner barrel removed; that core can then be extracted and is normally placed in a plastic guttering to support it. It is then passed to the geologists to allow them to carry out their analysis on it. Care must be taken when removing core samples, as some time there can be chemical reactions with the air. However one of the main problems can be trapped air as this can be under pressure. Core samples are often stored in fridges to preserve the core samples for later analysis. On some occasions small samples are frozen but I believe that this is more for microbiology.

On the question of how long can we run. This depends on the seabed conditions. The drill we have onboard will normally take around 3 to 4 hours to take a one-meter core. Our larger drill can take much longer to cut core and due to other operational requirements. One other point on how long things take, it also takes quite a long time to get the drill to the seabed and also to recover it. On this current cruise we will be working in around 4500 to 5000 meter of water. The deployment of the drill will take around two hours from surface to seabed. When the drill is on operation the ship will hold station-using DP (Dynamic Positioning). We will also have a transponder on the top of the drill to give us an accurate position of the drill on the seabed.

As for the costs and environmental impact I think one of the geologists would be better placed to answer that question.

I hope in some way this has answered your questions if you have any thing else you would like to know then please get in touch and I will be more than happy to explain what I can.

Kind Regards,
Iain Pheasant


Q

Will we ever be able to go to the bottom of the ocean and take pictures and beable to survive?
Veronica, Woodstock

A

Hi Veronica, We can actually do this now!  There are a number of manned submersibles (submarines) that can withstand the great pressure at the bottom of the ocean so that people can actually travel down to such depths, and there are also a number of remotely-operated vehicles that scientists can control from aboard a ship.  In fact, the BRIDGE rock drill we are using on this cruise can take pictures of the seafloor as well, so that we can pick exactly where to drill.

KAY


Q

Why do scientist study seafloor spreading? Why did the earth develop seafloor spreading? How would it be different if there was no plate tectonics?
Miranda & Brittany, Woodstock

A

Hi Miranda and Brittany,
We study seafloor spreading because we want to understand how our planet works!  Plate tectonics is basically the Earth’s way of getting rid of extra heat that’s generated in the core as radioactive elements decay.  Even though we think other planets have heat to get rid of, too, the Earth is the only planet that we know of that has plate tectonics!  Venus and Mars—the other two planets in our solar system that are most like our own—seem to get rid of heat via isolated volcanoes, and not by huge mid-ocean ridge systems and sliding tectonic plates.  Scientists don’t know yet what exactly caused the Earth to develop this process.  Right now the leading theory to explain this mystery is that Venus, for example, might not contain enough water in its mantle to allow the mantle rocks to flow and deform like silly putty. 
If there were no plate tectonics, life on Earth would be a very different place.  There might not be as much relief on the surface of the Earth, and what relief there was might be in the form of volcanoes rather than continents (plate tectonics is responsible for making continents and building mountains), so most of the planet might be underwater; there wouldn’t be any earthquakes; we wouldn’t have any coal or oil (because without mountain-building events, it would be hard to bury organic matter to the depths required to form these things)…  This is a very interesting question, and it’s very hard to answer, because plate tectonics has really dictated a lot of the evolution of life on Earth!  For example, amphibians probably evolved to become reptiles when the supercontinent Pangaea formed; since the interiors of continents are very dry, when plate tectonics caused Pangaea to form, a lot of frog-like animals suddenly found that their jelly-like eggs kept drying out, so they evolved to lay eggs in hard shells that kept the eggs alive in dry climates.  Without plate tectonics, it’s pretty likely that we human beings wouldn’t exist, so the more we learn about how and why plate tectonics works, the better we can understand how we got here.

KAY


Q

Was the missing piece of the crust caused by human activity or by natural causes?
Cody & Greg, Woodstock

A

Hi Cody & Greg, 
The crust in this part of the world is thin or absent because of natural causes. People don’t have the technology (or the desire) to remove huge amounts of rock around on the seafloor.  Of course, the big question here is, WHAT natural causes resulted in thin or missing crust, and that’s what we’re here to try to figure out.

KAY


Q

Information on your site noted that only about 25% of the mantle is molten. If mantle is exposed at some points along divergent plates, rather than being filled in by basalts, does that mean that melting is not uniformly spread throughout the mantle? Will this tell you something about the circulation within the mantle?
Kary Christoperson, USA

A

Hi Kary,
That’s a fantastic question.  Even though up to 25% of the mantle might melt by the time it is finished upwelling beneath a mid-ocean ridge, at any given time there is never 25% melt and 75% solid material in the mantle.  This is because as soon as melt forms in the mantle, the density contrast between the melt and the remaining solid is so great that the melt shoots upwards pretty quickly (the same way a less-dense bubble rises in a denser liquid).  One of the major questions in the field today is the question you just asked: is melt delivery uniform beneath the ridge axis, or is it focused towards the center of ridge segments and away from transform faults?  And if melt is focused in this way, is it because of temperature differences along the ridge axis or is it because the mantle is focused in this way too, and thus upwells faster in the center of ridge segments?  If we knew the answers to these questions, we’d understand a lot more about how mid-ocean ridges work, and that’s why we’re doing this research!

KAY


Q

Your work is great. I would like to ask if this crust hapen more frequently in areas close to the equator or it may hapen in the same way in polar ocean? Good job for all of you.
Luizinho Caron, Brazil

A

Hi Luizinho,
This type of phenomenon is related to the spreading rate of the mid-ocean ridge—the slower the ridge spreads, the more likely you are to see this sort of thing.  In fact, two of the slowest-spreading mid-ocean ridges on the planet are the Gakkel Ridge, which goes across the Arctic Ocean, and the Southwest Indian Ridge, which is between Africa and Antarctica.

KAY


Q

I was reading about your expedition and find it very interesting.  I plan to check back every few days and read the diaries posted.  Recently, I saw online a video about the idea that the earth is actually growing in size.  This was the first time I had ever heard of this theory.  Have you heard of this, and if so, what are your thoughts on it?  Could this "wound" that you are investigating be an indication of this "earth growing" theory?
Marcus Trisdale, Oregon

A

Hi Marcus,
Thanks for your interest in the project!  Actually, this missing crust is much more consistent with the theory of plate tectonics.  The Earth only gains mass from meteorites that land on our planet from outer space, and this is an extremely small amount of matter relative to the size of the Earth.  So, since the Earth isn’t gaining matter in any appreciable quantity, any expansion of volume would result in a reduction of density (since density is equal to mass divided by volume), and there is no evidence for this.  Furtheremore, if you want the Earth to expand at mid-ocean ridges, you wouldn’t be allowed to put any material back into the Earth at subduction zones, and we most assuredly do see subduction zones across the planet.  (We see direct evidence for this in the numerous volcanoes surrounding the Pacific Ocean, as well as in most of the planet’s major earthquakes, including the one responsible for the disastrous Indian Ocean tsunami of a few years ago.)

KAY


Q

Do You get seasick at all?
Kayla, Georgia, USA

A

Hi Kayla,
Nope, not yet!  But the weather’s been pretty good—hopefully we won’t encounter any storms, because that might be a different story.

KAY


Q

How is it that fish can live at the great depths and pressure you will be visiting.
Caitlin Peck, age 8, Idaho

A

Hi Caitlin,
The fish are specially adapted to live down there, and if you tried to bring them to the surface and keep them in a fish tank, they would die.  It’s just as hard for them to live up here as it would be for us to live down there!  Some of them have evolved special lights on their body (since it is totally dark down there), and near mid-ocean ridges there are whole communities of organisms that survive on a food chain that is based on the metals and hot water that comes out of hydrothermal vents (so if the sun were ever to go dark, they could still survive down there).
P.S. When we start drilling again, we’ll send some Styrofoam cups down to the bottom of the seafloor, and the great pressures there will cause them to shrink!  Keep your eyes peeled for some pictures on the website.

KAY


Q

In geology class, we learned that as the plates seperated, magma from the mantle rose up to fill in the "gap".  Why do we get magma instead of the actual mantle material?  Even silly putty will squeeze up into a crack.  Are there any theories as to why we don't have the normal basalt material in these areas?  Thanks and have a great trip!!
Christy, Arkansas 

A

Hi Christy,
Good question, and thanks for the good wishes.  The mantle beneath mid-ocean ridges experiences decompression melting (sometimes called adiabatic melting).  This works in the following way: Way deep down in the Earth, the mantle is extremely hot, but it’s under such great pressure that it stays solid.  As the mantle begins to upwell, it gets closer to the surface of the Earth and has less rock above it, so the pressure gradually becomes less.  At a certain point, the pressure is low enough that the hot material can start to melt, and this point is a function of both the precise composition of the mantle and the precise temperature of the mantle.  In most places on the Earth, this point is at about 60 kilometers below the surface, and the mantle melts as it upwells until it gets to the base of the crust (which is created by the magma that is extracted from the upwelling mantle) at about 7 kilometers below the surface.  So, usually, the model you describe is correct, especially at fast-spreading ridges.  However, if for some reason melting is not as extensive as it is normally, there might not be enough magma to fill in the “gap”, so you end up not generating much of a crust, and instead having a lot of faults that can expose mantle material. There are a couple of possible explanations for why a region such as this one might experience less extensive melting.  Two of the leading hypotheses are that 1) the presence of a transform fault might cause the mantle to be a little bit cooler at the ends of the ridge segments, or 2) the mantle might have a slightly different composition here.

KAY


Q

If you found the basalt layer missing from the seafloor where is it now? Would'nt that much rock make a huge pile that you could see?
Markus, age 8, New York

A

Hi Markus,
Good question.  When we say that the basalt crust is missing, what we mean is that all our scientific models predict that it should be here, but it turns out it never was here in the first place.  It just never got made.  This is probably because as the mantle upwelled beneath the Mid-Atlantic Ridge, it didn’t melt enough to make a lot of crust.  So all the crust-making ingredients might still be mixed up in the mantle because they never got extracted as melt, or it could be that the mantle here never had any crust-making ingredients to start with.

KAY


Q

As far as I understand the spot you are investigating is a piece of earth where no crust has been formed. What do you expect to find instead? I mean it can't be magma i guess because that would be cooled immediatly by the ocean water...I guess cooled magma is solid rock too, or am I mistaking...So what is the difference between crust and cooled magma?
Menno, Netherlands

A

Hi Menno,
You are correct that cooled magma is solid rock.  Oceanic crust is all made of cooled magma (or lava, if it has erupted to the surface and hasn’t cooled underground), and the rock that is the result of this is called basalt if it cooled quickly and gabbro if it cooled slowly.  Without basalt and gabbro crust, we expect to find mantle rocks.  In their pristine state, they are called peridotites, but mantle minerals are happiest at high pressures and temperatures, so when they come into contact with cold seawater, peridotites gradually alter to rocks called serpentinites.

KAY


Q

I was wondering if you know or are maybe expecting to find hydrothermal vents in this ridge since no cracks or fissures have not created new crust?  Also, compared to other ocean ridges what is the spreading rate of this area (fast or slow)?  Thanks and good luck!
Steve Durango, Colorado.

A

Hi Steve,
Great question, and thanks for the good wishes.  There are actually two kinds of hydrothermal vents: black smokers and white smokers.  Black smokers form at fast-spreading ridges (that is, ridges that separate at a rate of 5 cm/year or faster), and they are powered by the very hot magma that heats the area up to very high temperatures.  The water that comes out of black smokers can be as hot as 400oC. Meanwhile, slower-spreading ridges like the Mid-Atlantic Ridge (which spreads at 2.5 cm/year) have white smokers.  These hydrothermal vents may be powered by the exothermic reaction of mantle minerals altering upon contact with seawater or by magmatic intrusion, and the typical water temperature from these vents is about 250oC or less.  We’ll be keeping our eyes peeled for any hydrothermal vents we might run across (or rather, TOBI will keep its eyes peeled for us!). 

KAY


Q

Hello, could you please decribe in detail what peridotite is, (such as color, mass, hardness, general makeup, ect,) as compaired to basalt and other minerals found within the area you will be drilling in. Thank You and safe trip.
Janalee, Rhode island

A

Hi Janalee,
Thanks for the good wishes, and thanks for asking about my favorite kind of rock!!  A residual peridotite (we call it residual because it’s what’s left after the mantle partially melted) is essentially made out of four minerals: olivine (green in color, and about 70-80% of the rock), orthopyroxene (brown in color, and about 15-20% of the rock), clinopyroxene (bright green in color, and 5-10% of the rock), and an aluminous phase that depends on pressure (about 1% of the rock, and usually spinel, which is black, but at lower pressures plagioclase, which is white).  Peridotites in their pristine state are very dense, very hard rocks (if you’re familiar with the Mohs Hardness Scale from a geology class, olivine has a hardness of about 6), and they’re usually greenish in color (because of all the olivine), with a very coarse grain size (up to 1 cm).  Because these minerals are happiest at high pressures and temperatures, they will chemically react with cold seawater, usually forming the mineral serpentine, which turns the rock to a duller greenish or blackish (although you can still see where the orthopyroxene grains used to be when this happens). When peridotites melt, some of all the minerals turns into liquid, but clinopyroxene preferentially melts, followed by orthopyroxene.  So the more a peridotite has melted, the less clinOpyroxene and orthopyoxene we see in it.
Crustal rocks, on the other hand, are called basalts if they cooled quickly (and have a very fine grain size of less than 1 mm), or gabbros if they cooled slowly (and have a coarse grain size comparable to that of peridotites).  Basalt is sort of boring-looking and black, and gabbros are usually black or black-and-white mottled.  Because they’re made out of the melt that was extracted from the peridotites, crustal rocks have mostly clinopyroxene and orthopyroxene, along with plagioclase. They are also hard and dense when they’re fresh, but if they react too much with seawater, they turn into amphibole minerals (usually brown or green).

KAY


Q

Hurrah Kay A!  It's great that WY has a rep on this adventure! I'm especially curious about the temperatures being collected to calibrate the bathymetry measurements.  What's the range in these temps?
Cathy Russell, Wyoming

A

Hi Cathy,
Glad to hear that news of our cruise has made it all the way back home!  The sea temperatures range from about 25oC (77oF ) at the surface to only 2 or 3oC (37oF) at the bottom.

KAY


Q

Isn't the mantle made of really hot magma? How can it be exposed on the seafloor without turning into cold crust?

A

Most people know that the earth is divided into different layers (in the simplest model called the crust, the mantle, and the outer and inner core). What most people don't know is that the most important difference between these layers isn't their temperatures--it's their different compositions! So, when we say that the mantle is exposed at the seafloor, we mean that rocks made of mantle material are touching ocean water--we don't mean that there is a gaping hole filled with glowing orange molten rock! As it happens, there isn't really very much molten material in the Earth (with the exception of the outer core, which is very much deeper than anyone has ever drilled!)--in fact, the mantle beneath mid-ocean ridges only melts by about 25% at most, leaving solid residue behind! The lava that comes out of volcanoes at mid-ocean ridges isn't tapping a huge planet-wide reservoir of molten rock--it's the 25% or so of melt that is getting squeezed out of the mostly-solid mantle. The lava (or magma, if it stays underground and never erupts) is what the oceanic crust is made of, and it is compositionally different than the solid mantle "residue" left behind by melting. Now that we've established that the mantle is not a massive subterranean ocean of magma, it is worth mentioning that deep underground the solid mantle is still extremely hot. The process of plate tectonics works because, despite being solid, the mantle is hot enough to be able to flow like Silly Putty. The mantle rocks exposed on the seafloor at places like this one on the Mid-Atlantic Ridge were once this hot, but by the time they make it all the way up to the seafloor they've lost a lot of heat to the cold ocean water, so they're no longer hot--they're the same temperature as the seawater. (We call this process "conductive cooling", and you've experienced it yourself--this is why your coffee will eventually become cold in your coffee cup after it loses a lot of heat to the cool surrounding air.)

KAY


Q

How was it determined that the crust was missing in this area? Doug Sjostrom, Massachusetts, USA

A

Hi Doug. The main evidence we have is from rock samples taken dy dredging (dragging a steel bucket over the seafloor) and by robot manipulator from manned submersibles. In this area many of the samples are of mantle rocks, and the normal basaltic rocks of the ocean crust are missing.

ROGER


Q

Hi there I am a 8th grade teacher here in Brighton (USA), we were wondering as a class how far you are going to actually be drilling into the earth below the sea? Good luck from Brighton CO!
Eric Heinz, Colorado

A

Hi Eric, I particularly wanted to answer your question myself since (relatively speaking, anyway) you are so close to my home in Laramie! That’s a good question you’ve asked. We’ll be drilling many holes that are each about one meter deep. While it is possible to drill quite a bit deeper than this, drilling into solid rock is a slow process, and we’re most interested in getting a good geographic distribution of samples so that we can understand how this large area works! Tell your students to get out and enjoy the snow for me since I’m missing the last bit of ski season while I’m on this ship!

KAY


Q

If the flow of lava on the sea floor is expanding, would that make the oceans warmer? And since the currents run north wouldn't that make the polar ice caps melt?
Louie Mausser - Fort Myers High School, USA

A

Good question, Louis, and in principle you're right. The hot lava DOES heat the water, but the actual temperature rise is quite small. Ultimately this heat gets radiated up from the sea surface or transferred to the atmosphere, which then radiates it out into space. So the heat carried out of the mantle by the lava is just one step in the transfer of heat from the Earth's interior to space.

ROGER


Q

I recently read about a large fault generated at the time of the Asian tsunami- it is about 1000 kilometers in length as reported in BBC news. Is there any possibility at all - that there is some connection between the hole you are exploring and this giant fault line associated with the tsunami?
Jonathon Kosoy

A

Hi Jonothan, The crust on the ocean floor is covered with faults that develop for many different reasons. Faulting is associated with the exposure in our study area, but these faults are developed by the spreading action of the mid-ocean ridge as the plates pull apart, and so they are tectonically different to the fault that caused the Tsunami.

SAM


Q

How do you know the crust is missing in this part of the world?

A

Excellent question! Marine geology is a particularly exciting challenge because it’s really hard to learn about rocks that are buried beneath thousands of meters of water! Unlike geologists who work on land, those of us who work on ocean rocks can’t actually go and look at what we’re studying—we have to work from afar. Generally speaking, the easiest and cheapest way to find out what’s at the bottom of the ocean is to drag a bucket (called a dredge) across the seafloor and see what you haul up. In most parts of the ocean, the seafloor is made of a crustal rock called basalt, which forms from lava erupted at undersea volcanoes. Near the Fifteen-Twenty Fracture Zone, however, dredge hauls don’t contain much basalt—instead they contain quite a lot of mantle rocks (called peridotites). Since the original discovery of mantle rocks in this location, there have been a number of expeditions to the region that have provided two separate lines of evidence—geological and geophysical—that the crust is thin or missing. Rock samples that have been obtained by dredging, drilling, and submersible (including submarines and remotely-operated vehicles) provide direct geological evidence of thin or missing crust from specific locations. Meanwhile, from aboard ships scientists have measured very small changes in the strength of the Earth’s gravity and variations in the speed at which seismic (sound) waves are transmitted through the Earth, which provide geophysical evidence that mantle rocks may be present on the seafloor over very large areas in this region.

KAY


Q

Could this area be Atlantis???!!!
Michelle Henninger

A

Hi Michelle. This seems unlikely, but you never know, the lost city is still to be found! :-)

SAM


Q

Hello , I am most interested in this work that you are doing. Best to you all - Safe voyage. My question is: If the crust is not hardening, is the water going down?
Dorothy Draughn

A

Hi Dorothy, good question! In our research area the volcanic rocks that normally make up the crust are sometimes missing, exposing the mantle sequence below. The mantle rocks are solid, not molten, but they do take up some seawater as they react with it to form a new sequence of minerals, notably a soft green mineral called Serpentinite.

SAM


Q

Do you ever do any fishing to pass the time when you aren't working on the ship?
Joe Paz, New Jersey

A

Hi Joe. Unfortunately, when we have instruments deployed into the sea on cables, it's not a good idea to put other lines out there in case they get tangled up. Frozen fish fingers for us all the way I'm afraid!

SAM


Q

At the risk of sounding silly I’m wondering if the exposed mantle is near the area popularly called the Bermuda Triangle. Thanks- good luck with your work!
Chris Browne, Florida

A

Hello Chris. I think the 'Bermuda Triangle' area stretches between Puerto Rico, Bermuda and Miami (according to Google!) so it's closer to the Caribbean than where we will be sampling.

SAM


Q

Concerning the "missing crust" recently discovered in the mid-Atlantic, is there any indication of exactly how large an area of the mantle is exposed? News reports say "thousands of square kilometers", but that seems rather vague and uninformative. Can you give GPS co-ordinates so that I may mark the area on my map(s)? I must admit that this is fascinating to me. I wish you luck on your voyage, and a safe return.
Robert Cronner, Oklahoma

A

Hello Robert. The 'missing crust' isn't really just one distinct area where we see no crust at all. Rather, it's an area where the volcanic rocks which make up the crust are either thin or sometimes absent. As such It's rather difficult to quantify exact dimensions for any 'hole'. This situation isn't unique to our sampling area - across the globe there are many places at Mid-Ocean Ridges that we suspect or know are similar.

SAM


Q

Why is this happening in deep of Atlantic ocean, is it something really dangerous to humanity or is it something natural?? We’re very curious about it!! Good travel!!
Camillo Almeida, Brazil

A

Hi Camillo. The area of 'missing crust' is definitely a natural feature and has nothing to do with the actions of mankind. It poses no harm to humanity. It is a less well understood part of the global plate tectonic system that controls the destruction and formation of new crust on the planet's surface, and this is why it is so interesting for us to be able to study it and improve our models of how it works.

SAM


Q

Some questions for the team: 1) if the mantle is exposed, I believe it has very high temperatures, is it right? 2) is the magma exposed? 3) if yes, why it doesn’t cool down in contact with ocean water ? 4) what happens to the gas coming in contact with water and high temperature? 5) can it elevate the ocean temperature to any measurable degree?
Bruno Selimer, Brazil

A

The hot lava DOES heat the water, but the actual temperature rise is quite small. Ultimately this heat gets radiated up from the sea surface or transferred to the atmosphere, which then radiates it out into space. So the heat carried out of the mantle by the lava is just one step in the transfer of heat from the Earth's interior to space.

ROGER


Q

Since the Atlantic conveyor flows over this area and ultimately ends up in the Pacific Basin, could this become a suspect for increased El Nino activity?
Jim Woody, Texas

A

Hello Jim. Although the heat from the earth's mantle does heat the oceans when lavas are erupted at the surface, and affect the water chemistry, this effect is very small in comparison to other processes taking place in the oceans, and will have negligible effect on the flow of ocean water. Therefore there will be no knock-on effect to weather systems that we can detect.

SAM


Q

Is the North Atlantic Ridge the same area where you are going and the earths crust is missing, where several earthquakes have happened? This is VERY interesting...good luck!!! Stay safe !!! I have put this on "my Favorites" to keep track of your progress.
Patricia Goodwill, Canada

A

Hi Patricia. Yes, you're correct. At all plate-tectonic boundaries earthquakes occur as the plates are pushed together, pulled apart or grind past each other. There are tremendous forces associated with plate tectonics, and these cause the rocks to break in a brittle way (fault).

SAM


Q

Will you sample gases emanating from that "wound" and will you carbon-date them? methane is a large component of our core and a certain theory contends that most methane coming out of gas and oil holes is not fossil methane (non-renewable) but "original" call it "crystal" methane. the only crux is to encounter it from earths surface, ie get through the first 20 or so kilometers of crust. someone in sweden drilled along a meteorite impact "carrot" and found it at 10km seeping up along the crack in the granite crust. with this open crust wound in the atlantic, you might be 10 kilometers ahead and meet crystal methane seeping up???! The implication would be significant: if we could get at the original methane all our energy woes would begone, no?
Fred, US.

A

Hello Fred. I think that you are talking about gas hydrates here. Some of the sedimentary deposits on the ocean floor contain lots of CO2 and methane trapped in solid form. It has been known for this gas to be released by drilling or disturbing the sedimentary rocks in the past, but we are going to be targeting our smapling at igneous rocks such as basalt and peridotite, which do not store gas hydrates.

SAM


Q

If indeed the mantle is exposed over such a large area, what is the overall sea temp in that area as compared to the sea temp outside the "mantle zone"?
Ron Taylor, California

A

Good question! In fact, although the hot mantle does warm the sea above, there is so much water in the ocean, and it is so well mixed, that there is very little rise in temperature. Of course, where there IS crust, that has been built from lava flows, so they also warm the water by a tiny amount, and there is little difference in temperature between the two areas.

ROGER


Q

If the Earths crust is open and the sea water is very cold, why hasn't the crust closed?
Joe Overmars, Florida

A

Good question, Joe. The 'hole' actually refers to the fact that a particular sequence of rocks, the volcanics which form the crust, are thin or absent. Inside the 'hole' there is still solid rock, but it is peridotite, which are mantle rocks, not crust rocks. Any molten rock at the surface would cool quickly. This is what forms the glassy 'pillow lavas' that are found on mid-ocean ridges.

SAM


Q

What exactly can you learn or conclude from your drilling samples?
Alan Lee, UK

A

Hi Alan. We are hoping to examine the exposed mantle rocks through drilling and dredging. Once we have the samples we will be able to use their distribution and chemistry to build up a picture of the mechanisms operating in this area with very thin or absent crust. As to exactly what we will find, we'll have to wait and see!

SAM


Q

Bon Voyage! I will enjoy watching your endeavor. Best of Luck. Question: Is your chef worth his pots and pans? Thanks.
Jonathon Coates, Halifax, Nova Scotia

A

Definitely. The food is excellent!

ROGER


Q

I've read articles where we have gotten close to the mantle via drilling. Is this truly the mantle or is a thin "skin" covering the mantle? If it is truly the mantle will this be our first real look at the mantle?
John Bonglovanni, East Texas, USA

A

In reality the crust everywhere is a thin skin covering the though in some places it is thinner than others. There are other areas where it is thin or missing for various reasons, and drilling has reached mantle rocks in some of these places. What is unusual about the area we are going to is that it appears to be a large area of missing crust, and it looks as though the crust was never formed there in the first place.

ROGER


Q

I just read the news about your expedition and you mission, and found the whole situation very curious. The note was a bit confusing, and I'd like to clear what is happening. There is an area near de Caribbean in which there is a sort of a 'hole', exposing earth's core magma? In that case, shouldn't the water cool it off, like when it happens with volcanoes? Or is this matter exactly what you guys are going to investigate? Thank you for your time, and for the will to share the details of the whole expedition online. Keep it up. Cheers from Brazil!
Marcus Mendes, Sao Paulo, Brazil

A

The hot lava DOES heat the water, but the actual temperature rise is quite small. Ultimately this heat gets radiated up from the sea surface or transferred to the atmosphere, which then radiates it out into space. So the heat carried out of the mantle by the lava is just one step in the transfer of heat from the Earth's interior to space.

ROGER


Q

What chemical, geological or structural data exists to lead to the conclusion that the crust is missing at the mid-Atlantic redge?
Bob Melcher, Arizona

A

The main evidence we have is from rock samples taken dy dredging (dragging a steel bucket over the seafloor) and by robot manipulator from manned submersibles. In this area many of the samples are of mantle rocks, and thye normal basaltic rocks of the ocean crust are missing.

ROGER


Q

The big chunk of exposed earth's mantle underneath the Atlantic...how old is it? Is it relatively (geologically) newly formed? Are there other locations on the planet where there isn't a crust, just the mantle?
Scott Jay Regner, Baltimore, USA.

A

Hi Scott. The question of the mantle's age is an interesting one! In a sense, much of the mantle is as old as the Earth, and may have been moving around deep in the Earth for hundreds of millions of years. However, the mantle we see has only just appeared at the surface, geologically speaking (perhaps in the last million years or so), so in that sense it's very young. Yes, there are other places where there is no crust, such as parts of the Arctic mid-ocean ridge, which is spreading very slowly and apparently producing little or no lava.

ROGER


Q

What sort of temperatures can you expect to find at the points you're drilling at?
Anton Bear, Nottingham, UK

A

Hello, Anton. We will only be drilling down about 1 metre, so these rocks are about the same temperature as the water at the bottom of the sea: about 4 degrees Celsius.

ROGER


Q

Isn't the mantle usually many times hotter than deep sea water? Why haven't it turned to crust once it found water?
Vinicus Kamakura, Brazil

A

Hello Vinicus. Yes, the mantle is much hotter than seawater, and does cool molten lava at the surface. Where the crust is missing, the mantle beneath IS solid, not molten. Even though the 'hole' is filled with solid rock, it doesn't count as crust because crust is formed from volcanic rock called basalt, whereas mantle rocks (peridotites) are chemically very different.

SAM


More answers to your questions comig soon!


Home -

About

-

Latest news

-
Cruises
-
Learn
-
Facts
-
For teachers
-
Contact us

© NOCS
February 2007