Alvin 3358 - Dive Summary
19 February 1998
Observers: (Cindy Van Dover), Karl Grönvold (transcript)
Pilot: Blee Williams
Dive Summary
The dive began about 200 m west of the Oasis low-T Vent Site in heavily sedimented sheet flow - sample 1. Heading 110 this gave way to a very uneven (AA-like) broken up sheet flow, most likely with similar heavy sediment cover. There was then a relatively clear contact between this and a younger lobate flow with much lighter sediment cover - sample 2. This is a lobate flow with occasional pillows and extends to Oasis.
We arrived at the southwest margin of OASIS which begins as a bed of orange anemones (several cm diameter and height), giving way to orange anemones and barnacle (Neolepas zevinae) bushes with an understory of small (~1 cm height, diameter) grey anemones, and then to patches of mussels or clams within the anemone/barnacle bed. We sampled a total of 6 mussel patches within OASIS, working S to N along the margin of a drop-off. At the first 3 OASIS Sites, we took both pot and scoop samples; scoop samples only at OASIS Sites 4-6. Temperatures among mussels ranged from 4-6C. The entire N-S extent of OASIS is ~100 m and the eastern boundary is at the drop-off (collapse?); there is a gap in mussel patches within the middle of the field. Anemones do occupy the lobate field E of the drop-off, and there are patches of long-dead mussel and clam shells, as well as an inactive sulfide chimney (13 m) covered with serpulid tubes. Debris (anchors, cables, markers) from an old Japanese/Shinkai experiment was observed throughout the OASIS field.The lobate lava with occasional pillows and pillow groups continued north of Oasis and all the way to Stanley. During the passage however a change was observed which was mainly manifested in more glassy loabates. With no clear difference in lava morphology - no firm contact was registered but we may both have traversed possible contact again and even travelled along it.We reached Stanley (Mkr #21; named during the Lilley/von Damm cruise) toward the end of the dive and explored the area, looking for mussel beds with no success. The local area supports some anemones and at one time supported a few mussels, clams, and serpulid worms. The site hosts an active sulfide chimney.
Sample Locations:
Navigation Plot (GMT)