Dive Summary by Debra Stakes
We returned to the Flyer Hydrothermal Site at the beginning of Dive 179 with the CTD mounted on a T-handle in an attempt to measure the fluid temperatures. After a brief survey we found the mound and deployed an MTR (miniature temperature recorder) that records temperature every 11 minutes. This was left within an excavated site with robust flow for 75 minutes. The CTD worked very well for this low-temperature site. The ambient temperature was 1.9 C. The first vent, near the MTR, recorded temperatures up to 4.9 C. Another venting site recorded temperatures up to 6.8 C. We attempted to sample the flocculent material using a sediment push core. Three push cores were collected at the Flyer Vent Site. An acoustic beacon was left to mark the site. For the next segment of the dive, we traversed along the eastern side of the massive pillow flows to determine the extent of the low temperature venting. The obvious vents with yellow bacterial mat extended as a ridge for several hundred meters, but then disappeared.
We continued on keeping the contact with the large pillowed front about 100-200 meters to our west, traveling in mostly older sedimented pillowed terrain. We followed the next conspicuous flow front from east to west and determined that it was comprised entirely of pillows, flow tubes and hornitos. Our dive plan included a detailed inspection of the age relationships between the western edge of this constructional feature and the pair of faults that bound the inner valley. The terrain between the two faults was structurally complex with numerous steps and wide fissures. Wherever possible we examined intact exposed walls in detail to determine the lava stratigraphy. The dive was completed by traversing down into the axial valley and across to the cleft at its center.
During the dive we collected 14 grab samples and seven wax core samples. This was in addition to the sediment push cores collected at the vent site and 8 biological samples collected at the vents and elsewhere.