JC010: Mud volcanoes and submarine canyons


 JC10



Cruise diary


Day 11: Tuesday 12 June 2007
Position: 39° 29 821N, 09° 55 980 W
Weather: Calm seas, cloudy but bright skies


Helen writes:

"Today started early, 3.30am again! The ROV was carrying out swath bathymetry, creating a 3D map of the Nazaré Canyon, and as it was being kept at constant height I was allowed to pilot her for a while. I was just using a touch-screen computer, rather than the joysticks and had to choose the path taken by the ROV. It was quite simple, just choosing steps of 50m for the long stretches, and then changing the heading (way she’s facing), and adjusting her direction slightly left (port) and right (starboard). I had to look at the monitors to check the distance from the next or previous way point, check her depth and keep an eye on sonar (showing any upcoming obstacles) and the swath, showing the pattern of the sea floor below. I really enjoyed it and hope I have the opportunity to fly her again!

I spent some time this afternoon editing video footage of the megacores that we have worked on, which we will send for you to watch soon.

We saw some amazing sights on the ROV screens this afternoon - what looked to be sharks trying to feed on bait that had been attached to one of our landers. We still have to have the species confirmed, but its quite exciting, as we weren’t expecting to see anything like them!

Having spent a while trying to confirm whether these fish were part of the shark family or not, a competition then ensued in the main lab to see who had the worst song on their Ipod! It was quite a battle, and lasted some time, but I think we all had a terrible song or two. It turned into a game of name that tune!

I get to see some more experiments tonight and tomorrow, and a range of sampling techniques that I haven’t yet met. Piston cores and CTD measurements among them. I’m not sure whether I’ll be needed to sift mud in the early hours of the morning or not yet, but I’ll let you know what I’ve been up to tomorrow!"


Virginia writes:

"Last night I slept very well. I didn’t hear the James Cook’s heart (the sound of her machinery) working. Usually I wake when something changes on James Cook.

ISIS Dive Plan 48 has been running since yesterday evening. This plan includes 24 push cores (some reference push cores for Jeroen), starting Jeroen’s experiment, finishing Teresa’s experiment, some swath bathymetry and doing a video survey of south canyon wall. I am waiting for an opportunity to talk with Jeroen about his experiment - look out for this in the forthcoming days.

Yesterday Andy told me that I think about forams as a geologist, rather than a biologist. In fact my work has an high affinity with the aims of Raquel or Doug’s work. Raquel for instance is studying the history of the Portuguese Canyons during the Quaternary period – the last 1.8 million years (see Raquel’s interview here). To study such a long period of time she will need a long sedimentary record (layers of sediment that have built up on the seafloor over time) which will be collected using a piston corer.

Diferent sediments on the Nazaré Canyon floor related to different current activity. These environments each provide different conditions for the animals that live there. Benthic foraminifera assemblages, for instance, should be diferent in number and species diversity in each of these areas.

I also like to study sedimentary sequences recovered from the sea bottom. These sequences can potentially record many climatic changes which have influenced oceanographic conditions. It is important to understand what the sediments can tell you about the past, and this includes the fossils contained in it, such as foraminifera. They can give us an idea of the oceanic conditions at the time they died. So people who study microfossils need the results obtained by biologists like Andy to have a better understanding of seafloor ecosystems and their reactions to environmental changes.

Looking at a fossil record is much like reading a story, and I like to hear interesting stories. When I was a child, my grandmother told me lovely stories of princes and princesses. But if I become a grandmother I want to tell my grandchildren other kinds of stories. My stories would be about climate change during the most recent geological period of the Earth’s history, the Quaternary. During this time, thick glaciers advanced and retreated over much of North America and Europe, parts of South America and Asia, and all of Antarctica.

Ice caps over the Europe and northern areas during
a very cold period - the Last Glacial Maximum
(20000-17000 years ago).

Ice caps over the Europe and northern areas
during a warmer period (4000 years ago).
(Images adapted from Anderson & Borns Jr., 1994)

These climates influenced the shape of continents and oceans, and the organisms that live there. Several species disappeared (extinction of large mammals in northern areas), whereas others were evolving. Modern humans, for instance, have evolved in the last 100,000 years. These climate changes are recorded in sedimentary sequences in rocks.

See how the Portuguese coast changed during the last 18.000 years (according to Dias et al., 2000).

 

But if we look at the sedimentary record over a much more longer period, we find a great number of sea level fluctuations.

Sea level changing in the last 140000 years (adapted from Shackleton, 1987).

Climate is changing now. How will the changes in climate will affect life on Earth? Perhaps undertanding the past history will help us predict the future evolution of Earth, and Raquel and Doug's work will make an importnat contribution to this. However, their work also requires detailed knowledge of the present-day conditions: oceanic and continental conditions, biodiversity, web-foods, etc...."

References

Anderson, G. B. & Borns Jr., H. W. (1994) – The Ice Age Wolrd. An introduction to Quaternary history and research with emphasis on North America and Northern Europe during the last 2.5 million years. Scandinavian University Press, Oslo Norway, 208 pp.
Dias, J. M. A., Boski, T., Rodrigues, A. & Magalhães, F. (2000) – Coast line evolution in Portugal since the Last Glacial Maximum until present – a synthesis. Marine Geology, vol. 170, pp. 177-186.
Shackleton, N. J. (1987) - Oxygen isotopes, ice volume and sea level. Quaternary Science Reviews, vol. 6, pp. 183-190.



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