Archive of September 19th, 2007

Teacher at Sea log for Wednesday September 19, 2007

Happy Talk like a Pirate Day!! We have had a lot of fun with that today. ARGGGG.

We began the day with Jason 2 coming aboard the ship. The sea is rough compared to the first dive and it took more finesse to get Jason aboard the ship. The men worked as a team, and were able to get the both the Jason 2 and Medea aboard with no problems. I am happy to report that our first foam cup cast was successful. Now I will repack the boxes and nets for the next dive.

The scientists got right to work rinsing and identifying, drawing and examining the rocks. They sketch each rock; measure its length width and height. Then they look for glass and describe the thickness of any glass in millimeters. They describe the thickness of the manganese coating and whether the rock is sedimentary or lava. They look at the size and shape of the bubbles (vesicularity) and determine what percentage of the rock is bubble and what percentage is solid rock. Then they make a description of the degree of weathering.

We will put Jason 2 back into the ocean in the middle of the night tonight. We expect the length of the next dive to be at least 36 hours. We will make a decision on when to pull Jason out by both he work and the weather.

Last night I sat down with the Captain to learn about Navigational mathematics. He let me borrow this amazing book, The American Practical Navigator by Bowditch, that had so much great information about navigation and map reading. It gave all sorts of methods for plotting ones course while considering the curvature of the earth and the declination of true north, wind direction, current and many other factors, which effect how you set your course. Now I know why we learned trigonometry in school!

Science Update by Todd Bianco

The dive at Site 02 was very successful. The objective was to examine and sample the western side of the large bathymetric feature south of Kauai. We targeted an uphill transect looking for changes in morphology as the bathymetry got shallower. Then we aimed for some more of the conical and pancake structures that are very clear on the side scan maps. The samples were mostly taken from intact pillow lavas that were often covered by thick sediment, but sometimes stuck out well above the sediment. Intact pillows like these indicate that at least some of our samples are local to the sight, although we suspect that some were transported here, perhaps in a mass-wasting event. In all, we retrieved twenty-seven samples during the survey.
Although many samples appeared to be sediment or highly altered basalts on the Jason 2 cameras, at the surface we found the type of lava that is desirable for geochemical analysis. In particular, the samples had glass rims, and glass is the preferred phase for trace element geochemical analysis. This is partly because it forms directly from the liquid magma without undergoing crystal fractionation, so the glass will have an incompatible trace element composition most like the original magma source. Also, we can confidently say that the glass came from a local magma source, rather than the crystals, which may have a more complicated history.
Along with the lava samples, we recovered a variety of beach sediments, and we have observed a lot of coral deposits on the seafloor. Where all of this coral and sediment are coming from is a mystery, but we can use these sediment samples to investigate that question.
Tonight we are heading down the axis of the south Kauai feature, as far south as 21 N. This takes us to the distal end of feature, where Site 03 is located. During the trip we will be collecting gravity, magnetic, multibeam, and side-scan sonar data. The gravity and magnetic data will be part of a later analysis, but the improved mutibeam and side-scan data can immediately help us identify the most strategic spots to send Jason 2 to look for sample sites.

Presented by the School of Ocean and Earth Science and Technology at the University of Hawaii, with financial support from the National Science Foundation.