Diary

R/V Pelagia Cruise CARBONATE

Friday-Monday, 19-22 October ‘07	In the early morning, with Galway in sight, Jan-Willem and Jack are busy packing equipment… [Photo: Henk de Haas]
the morning of the 19th the weather was fair enough to start with a hopper camera run. The plan was to find a suitable location to take a box and a piston core away from the mounds. We needed a spot without any cemented layers of corals and stones. So an area with sediments that accumulated on the northern Porcupine Bank without the influence of cold water corals and without nearby mounds affecting the local currents, and thus the sediments being deposited.
The idea is that from this core we could learn how the general current pattern has been during the period that the mounds have formed. Once we know that we will be able to determine the role of the general current pattern on the formation of the mounds. So by comparing the core taken from outside the mound area with the core we plan to drill through a mound next year we could for instance see that corals start to grow when the current velocity is above a certain level, or maybe the other way around. However when the camera run was performed and a suitable spot had been found the wind had increased that much that it was not longer possible to take a piston core. But since it was still possible to use the hopper camera we decided to do a little project Boris and I had in mind. One day Boris showed me a map on which some mounds are visible at the base of the slope of Porcupine Bank in a water depth of about 2 km. These mounds look exactly like the ones at about 700 metres depth on which we find the corals. So maybe these mounds are formed by cold water corals as well. We sailed to these mounds and lowered the camera and……. Nothing. There were no corals of the familiar species Lophelia pertusa and Madrepora oculata to be seen. We saw mainly sand and rocks and rocks and sand. So although the shape of these deep mounds is comparable to the shape of the more shallow mounds their origin appears to be completely different. What the origin of these deep mounds is, we still do not know. We sailed back to the mounds on the Porcupine Bank. Meanwhile the wind had increased again and we had to wait for better weather before we could start working. The next morning, so on 20 October, we tried to take the planned box and piston core in the area away from the mounds on Porcupine Bank. After three attempts we had to give up. The waves were that high that the box corer could not be placed at the sea bed in a controlled manner. The result was three heavily disturbed sea bed samples that could not be used for anything. The only thing we could do was to run seismic lines across the mounds first and try to take the cores afterwards. In the morning of the 21st all seismic lines we needed were recorded. They gave us a good impression of the height of these mounds and we think there are some suitable candidates for drilling. So although the weather was not really nice during the seismic recording, the results look good. It was clear from the early morning on that the weather was still too bad to even try to take a box and piston core. Instead we recovered BOBO. Because of the rough weather we did this with more people on deck than normally and it went well. BOBO was safely secured on deck and there was only one thing we could do: going to Galway. The weather forecast showed that the wind would not cease in the near future so it was useless to stay at this location and wait for better times. This morning (Monday, 22 October) we dropped anchor in Galway Bay. The entrance to Galway harbour is just a few miles away, but we can not get in yet. Galway harbour is locked by a gate which only opens 2 hours before high tide and closes at high tide. At this moment everybody is cleaning the labs, storing away equipment, preparing the loading of fuel and food once we are in port, etc., etc. In other words, for the scientists it is the end of the cruise, while the ships crew is preparing the next. All the scientists and technicians will go home sooner or later this week, as well as most of the ships crew. Only Anne and José will stay on board and make another trip. But that will be another cruise… This cruise is over…
Henk de Haas