Monterey Bay Aquarium Research Institute

West Coast Expedition
July 20 - August 30, 2002
West Coast of North America

July 24, 2002: Day #5

Log Entry: T450 and T451 (7-24-2002) N. Escanaba Cones

Dive T450, to sample a series of small volcanic cones at the northern end of Escanaba Trough, was terminated after the Kraft manipulator arm malfunctioned at 2000 m depth during the descent, despite extensive repairs yesterday. The day also began with fewer computer network problems and the navigation system was booted up quickly, although we began the dive without access to the servers to store frame-grabs or video annotations. These network problems were solved during descent and all computer systems are now back to normal operations. Much of the day was spent rebuilding the Kraft manipulator (again) and building a backup release mechanism to trigger water samplers using the Schilling manipulator. The Kraft manipulator repairs were completed before dinner and the vehicle was launched to test the manipulator at depth and to try to complete the highest priority portion of the dive on the volcanic cones planned for the day. The manipulator again malfunctioned during descent, but was usable with its extension range reduced somewhat.

On dive T451, we landed in the crater in the center of the volcanic cone and worked our way up the north crater wall, encountering large blocks of talus consisting of angular lava fragments from the coarse interiors of thick lava flows or a lava lake. No columnar basalt was observed during the transect. We collected 8 lava samples, particularly near the top of the cone where large glassy pillow basalts and lobate flows were encountered. This sampling was complicated by yet another malfunction, this time of the sample drawer on the vehicle, which would not close. This problem made sampling more difficult and obscured much of the field of view of the video cameras for the duration of the dive. It turned out that the obstruction was caused by a large rock that had jammed behind the drawer, and so became a sample!

One of the goals of the dive was to test a new 29-sample suction sampler designed to collect volcanic glass or small animals. The tests were completed and three glass samples were acquired, as well as a small sponge and brittle star. A valve installed to divert the suction to either the glass sampler or the standard biologic suction device did not seal properly, so suction was split between the two devices, making both less efficient.

In addition to the rock samples we also collected 3 push cores in hopes of recovering small glass bubble-wall fragments indicative of strombolian eruptions. One of the cores was also used to collect a small anemone and a small sea star. Two predatory tunicates were collected using the biologic suction sampler and placed in boxes in the drawer. The flat top rim of the volcanic cone was heavily mantled by sediment, although occasional small collapse structures were observed and more common pillow mounds projected above the nearly flat-lying sediment. The dive was ended after all primary goals of the dive were accomplished after about 3.7 hours on the bottom.

-- Dave Clague

The new glass suction sampler, in use for the first time. With the manipulator holding a T-handle attached to the sampler, we smashed the sampler's nozzle against the fragile, glassy surface of a lava flow that was otherwise too large to collect. The loosened glass fragments were vacuumed into a small canister mounted in a carousel on Tiburon's toolsled.
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This is a predatory tunicate found in mud rather than attached to rocks. It has only been seen a few times before. It was collected, and it contained the commensal polychaete always found living inside predatory tunicates. (The manipulator arm is in the foreground of the image.)



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