Dr. Joe Resing analyzing samples from the water column on the NeMO CTD Cruise.

R/V Wecoma - CTD Cruise
Science News

Science Report - Friday, July 30, 2001
Position - 44 20.398' N /129 59.387' W
Joe Resing

If you've read the previous reports, I think Ed has done a good job of touching on many of the aspects that go into what happens on an oceanographic research vessel and more particularly into what happens during our cruises to study underwater volcanoes. He's probably mentioned, for instance, that the ship is going 24 hours a day seven days a week. Well, as fate would have it, I am on the midnight to noon watch. About 10 days into the cruise, my body finally adjusted. As I write this report it is 1:00pm and I am getting ready for bed.

I am an ocean chemist and when I take water from the hydrocasts that Ed mentioned, I look for chemical clues that will tell me about the volcano. I measure Fe and Mn which are leached out of the solid lava. I also measure pH. Differences in pH tell me how much carbon dioxide gas is coming out of the volcanoes. When I combine these chemical clues with other physical measurements, I get a very good idea about the magmatic state of the volcano. For the most part, my measurements show a large decrease in the gas content of the fluids from Axial Volcano, consistent with the continued decay of volcanic emissions following the eruption of Axial in February of 1998. What seems surprising to me is that it is still pumping out a lot of hot water rich in chemicals. The majority of underwater eruptions studied so far showed a much more rapid decay in the out put of their eruption associated chemicals.

To make these measurements I use a shipboard chemical analyzer to measure Fe and Mn, and a pH meter to measure pH (in the picture I am analyzing another sample for pH). I also operate an instrument that will measure Fe, Mn, and pH under water. I place the instrument onto the CTD package and as it is pulled through the water as Ed described I obtain a picture of the distribution of these chemicals above the volcano. This instrument is an in situ chemical analyzer. Oceanographers have a funny leaning towards making acronyms for everything. For instance my predecessor, who had this instrument developed by the engineers at the Pacific Marine Environmental Lab referred to it as the SUAVE (Submersible Analyzer to Assess Vented Emissions). I found this too cumbersome, and I simply refer to it as the Vents In Situ Analyzer or VISA.

Well, I have one more midnight to noon watch to go and then it is back to being a daytime person again. We are almost done, and despite some equipment problems, this cruise has been extremely successful. We have collected over 250 samples for salinity, 350 samples of particulate matter, 400 Helium samples, 550 Fe and Mn samples, and almost 1000 pH samples. This information will be quite valuable in assessing the current state of the volcanos along the Juan de Fuca.