Monterey Bay Aquarium Research Institute

Gorda Ridge Cruise
August 5 - 21, 2002
Logbook

August 7, 2000: Day #3

Dave Clague writes: Dive 187 explored a section of the northern Gorda Ridge hypothesized to have had an eruption in 1996. After a thorough search, we did not locate any new flow and conclude that the 1996 eruption occurred only in the more northerly of the two sites inferred to have been active.

During the dive we also examined and sampled the largest flat-topped volcano along the Gorda Ridge and found that the steep sides are entire rock talus and that the flat top has many collapsed areas characteristic of lava ponds, as we have proposed in a recent paper on similar features around Hawaii. We also collected samples from about a dozen eruptive vents, most of which appeared relatively old due to their thick sediment cover. However, the recovered samples are almost all remarkably fresh, indicating their youth and suggesting that age inferences based on photographic data alone are misleading in this region of rapid sedimentation. We also discovered several areas in the neovolcanic zone that are sliced up by abundant faults and fissures, indicating that parts of the neovolcanic zone have not been volcanically active for longtime periods.

All day Monday, the winds built up and Tuesday began with choppy seas and strong winds, so we are postponing today's dive for a while at least, so our night coring operations will be continued this morning.


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