Seamounts Cruise
April 28, 2004, Day 2

The news today is better: we dove on Rodriguez Seamount. We had gone there last October when the weather was too bad to go to the Taney Seamounts as planned; this time we chose Rodriguez because it is closer to home. With our late start we would not have gotten a dive today if we had gone to the seamounts farther south.

We dove on the northwest flank of the volcano, from about 1200m up toward the summit at 660m. Rodriguez appears to have been an island for part of its history. Most of the flank was lava talus and volcaniclastic material (volcanic rock fragmented either by explosive eruptions or upon entry into the ocean). We collected 24 rocks (lava and volcaniclastic), sediment samples, and 14 animals for the biologists.

It was beautiful but windy with a good chop splashing up out of the moon pool in the center of the ship. The surface waters were very green and had a lot of large marine snow flocs.

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Basalt sample being collected from the face of a lava flow




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Pitted, eroded pavement, as we typically observed for volcaniclastic material




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Crab clinging to a glass sponge with small gorgonians nearby and a trumpet-shaped sponge in the background




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These ~1/4 meter high ridges in the volcaniclastic rock are slightly more resistant to erosion than the surrounding rock. Circulation of fluids through fractures altered the rock, possibly soon after it was deposited. The angular pattern of ridges has collected basalt talus that slid down-slope.



Nudibranch_03_06_00_18.jpg (117201 bytes)This lovely, ~10 centimeter-long nudibranch was one of a pair we saw. Nudibranch translates to "naked gills". The translucent frills along its back are the gills, which absorb oxygen and release carbon dioxide.


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