JC24: Dating volcanoes on the Mid-Atlantic Ridge


Cruise diary

Wednesday 28 May 2008

It was decided at yesterday’s science meeting that the more northerly traverses would be extended east for several kilometres, so that more of the area can be included in the TOBI survey. This is because the north-eastern area of the AVR has provided a lot of discussion in the past few days. Previous surveys have dredged some very magnetic rocks (“magnetic enough to pull the nails out of your boots” according to Maurice), which is an indication they may be fairly young, while our preliminary TOBI results seem to show bright (therefore fairly unsedimented and probably young) sheet flows ponding against faults. This combined with high light scatter and possible hydrothermals make it an interesting area for further investigation. In fact, the north-east is looking so promising that today the team have decided to add an extra west to east TOBI traverse to the north, so that we can collect magnetics and build up a digital mosaic of the area, like we are doing already for the rest of the AVR.

Today’s science meeting was mostly spent planning where we’d like to explore with our first few Isis Dives. Isis is a remotely operated vehicle (ROV - pictured to the left), which can be ‘flown’ around the seafloor. It has several video cameras, which the scientists will be using to identify and study different types of lava flows, two mechanical arms for collecting samples and an echosounder, which produces very detailed maps of the seafloor. We have time on this cruise for approximately 15 Isis dives, each lasting one and a half days. Around half of these will be spent using the echosounder to produce detailed topographic maps, leaving between 6 and 8 dives for sampling. With so few dives to cover the area and so many things required of them, it’s essential that they are very carefully planned to make sure we sample the whole area and maximise their usefulness.

Three dives have been planned so far, each targeting areas which, from the TOBI data, look like they may have recent sheet flows or boundaries between lava flows of different ages. These dives also take in a number of volcanoes and areas of higher elevation where cold water corals may be growing, which would be of interest to Kirsty, our on board biologist.

Of course, none of this would be possible without the support of the crew and technical support staff and it is only by working closely with them that we are able to complete our scientific objectives and stay afloat. Over the next few weeks we’d like to introduce you to everyone aboard the RRS James Cook….

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May 2008