Cruise diary

Monday 21st July 2003

Dave writes...

"On the morning shift Tina and I watched the sun rise (ahhhhh) - we were astonished at how quickly it became light. Today is beautiful, the sun is out and the water temperature is 29.3ºC.

The boy Dave on deck

The view from the ship at 5am local time

We are not really doing much at the moment but the work load will increase dramatically once we reach the Carlsberg Ridge. We will confirm that we are over the Carlsberg Ridge using the multi-beam which sends a sound pulse down the water column then rebounds off the sea bottom. The refelcted signal is then read by a receptor on the bottom of the boat which can be translated into a topographical map.

Once over the Carlsberg Ridge and between the shoulders of the ridge edge we will start dredging for samples. We are taking samples to firstly prove that an active ridge occurs in the position where it is thought to exist. We are trying to determine the extent to which a possible mantle plume interacts with the mid ocean ridge and whether it has a greater influence toward the plume's axis. This can be done by looking at trace element geochemistry such as the rare earth elements, primordial helium and the amount of titanium oxide in relation to niobium and neodymium. To determine this graphically we compare the samples to Normal mid ocean ridge basalt (N-MORB).

Plumes cause hotter material from deeper in the mantle to rise to the surface. When this interacts with a ridge, the mantle melts far deeper, at higher pressure and at a higher temperature. The mantle at this depth is less depleted with more variable mineral assemblage. This clearly effects the elements that are released to the melt which produces enriched mid ocean ridge basalt (E-MORB) which is what we expect to find at the Carlsberg Ridge.

At 7pm the bond opened. The bond is basically a tuck shop but it only opens for half an hour twice a week. The science team's morale was visibly lifted with the fresh supply of chocolate, fags and shower gel (Andy)..."

Tina writes...

"We are still travelling towards the next waypoint (at about 8 knots). I spent most of my watch on deck, watching the sun come up and then watching a small weather system move from the east to the west. There was a bank of very dark clouds and rain, but we missed it (I was almost disappointed). Whilst everything is quiet, we are doing log entries every hour and bringing work (mainly reading) with us to stay busy (and awake).

Today the crew and technicians have been trying to fix the CTD load cell (pictured below left), so that it can be dropped further than 600m. They have been working aloft in the very hot, humid weather most of the day (not much success so far, the problem seems to be more electronic than mechanical).

We are keeping in touch with the outside world via the wonderful IT group, who are out here from the SOC. Twice a day emails are relayed to and from the ship to shore. Mail is very important on board, for morale while away from our homelife. Each day, the incoming mail list is posted on the door of the computer room, so we know to expect some news!"

Crew working on fixing the CTD load cell

Liz: an IT guru

Carla: MAPR guru

This evening we had a talk from Carla about how to configure the MAPR, which is tied to the dredge line 1m above the bottom of the line. MAPR stands for Miniature Autonomous Plume Recorder, and it is designed to detect the tell-tale particles that would indicate a mantle plume or a hydrothermal vent. In those cases, the number of particles (and their density in the water column) would increase due to minerals and dissolved compounds. A graph of these particles against depth, measured with a nepholometer, is downloaded when the MAPR gets back on board the ship. Then Carla can decide whether a CTD drop should be carried out.

This evening the 3.5kHz ‘fish’, which measures the ocean floor bathymetry, crashed, and Chris Hunter from the OED is at this moment rebuilding some of the bits! One thing to remember on a cruise like this is that the crew, scientists and technicians have to be self-sufficient. They need to be able to improvise and fix the equipment without access to the workshops and facilities they would be used to on land.

This evening the ‘bond’ was open, this is an on-board shop that sells contraband items like chocolate and cigarettes. I had about 7 requests for T-shirts from friends and family, so that’s what I bought. Later, we set up a projector in the main lab and played a DVD of The seems very normal on board!"

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