Seamounts 2003
October 11- October 17, 2003


October 12, 2003
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This clam lives like a brachiopod, attached to rocks with a clump of threads called a byssus. We have seen these on Davidson Seamount and the President Jackson Seamounts off Gorda Ridge, and we expect to see them on Rodriguez Seamount if we get deep enough.

David Clague writes:
Taney Cruise Report for dive 627.
We are clearly going to have to rename this cruise as we now have no chance of getting to the Taney Seamounts because of gale force winds and large storm-generated swell from off British Columbia. We began this leg under a cloud of ominous weather forecasts and decided that our chances were greater to be able to dive if we postponed heading west to the Taney Seamounts. We finally departed at 2:30 Sunday heading northwest to Pioneer Seamount, where we dove at dawn Sunday morning. The seas and wind were marginal for a dive, and as they both increased during the morning, the dive was aborted at noon after about 4 hours on the bottom. Despite the short duration of the dive we collected 8 lava samples from outcrops and numerous animals including crinoids, brisingids and other asteroids, ophiuroids, gorgonians, hydroids, clams, a stalked tunicate, and a pycnogonid that forgot to let go of the rock he was hiding on. Other animals observed during the dive included glass sponges, cucumbers, soft corals, anemones, rattail fish, skates, snail darter fish, and featherduster worms. The assemblages are quite different from those on other nearby seamounts with different gorgonians and asteroids, but the same old sponges, cucumbers, anemones, soft corals, clams, and millions of ophiuroids. The lava flows were thick blocky types that we usually see nearer the tops of nearby seamounts. No pillow lavas were observed, reflecting the low-temperature, viscous characteristics of the lava. The common yellow sponge seen on Davidson Seamount in such abundance was not observed, and only a few specimens of the large bubblegum coral were seen, although this may simply reflect that the dive did not reach the summit of the seamount.
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Basaltic lava rock, sampled with the manipulator. This rock has a thin layer of volcanic glass on the top surface (not easily seen in the photo, but obvious upon a closer look on deck). The lava quenched upon contact with the cold seawater, trapping the gas and mineral composition of the melt in the glassy surface. So analyzing the glass, if it hasn't been altered too badly over the ~10 million years since it erupted, will give insight into the eruption conditions, such as depth, temperature, and whether the magma was stored for long in a magma chamber before it erupted. 

After examining an even less promising weather report, which indicated we were unlikely to be able to dive at either Pioneer or the Taney Seamounts before Wednesday or Thursday, we made the decision to head south and away from the storm that is producing the large swell. By dinner Monday, we should be at Rodriguez Seamount offshore from Pt. Conception, hopefully having eluded the wind and swells that caused us to shorten the dive today. More news after we get to Rodriguez and do the first dive on this previously unexplored seamount.

--David Clague

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Glass sponge, festooned with crinoids, and home to a small shrimp (seen peeping from within the sponge in the lower center). These crinoids, also known as "feather stars," can swim. Other crinoids we saw today have tall stalks and can crawl if knocked over. They are being studied by a biologist in our science party, Chuck Messing.

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