We started later than usual today
following the marathon day and night yesterday. The ROV hit the water at
8:45 am and then had a slow descent as the engineering department made
adjustments to the level-wind on the drum that handles the tether for the
ROV. The dive was located on a series of submarine vents starting at about
2050 meters depth. The cones are related to the rejuvenated stage Koloa
Volcanics on the south flank of Kauai, and are located close to the site
of the dive on May 10.
The main objectives of the dive were to sample
glassy basalt for volatile analyses and to observe the eruptive deposits
on the cones to understand more about submarine eruptions. The first cone
was an immediate surprise in that its surface was almost entirely covered
by agglutinated spatter instead of the expected pillow basalt and
hyaloclastite. The next two cones consisted almost entirely of
hyaloclastite, some containing dense basalt clasts, and some spatter. We
finally found pillow lava on a ridge at the base of the fourth cone we
observed. However, the main cone appears to be of hyaloclastite yet again,
although we only saw the base of the cone before ending the dive.
In processing the rock samples in the lab this
evening we found that one sample has a breadcrust texture and another
appears to be a volcanic bomb. We are finding that submarine eruptive
products are more similar to those of subaerial eruptions than is
generally believed and that spatter, previously undescribed from the
submarine environment, may be a common submarine eruptive product. We
collected yet another new sea star (nine-legged), a large sponge and a
blue-purple sea cucumber. The cucumber was quite a troublesome critter,
floating from the biology box and having to be recaptured. We have enough
video of this particlar sea cucumber and his capture (twice) to make a
short comedic movie! Tomorrow we will return to a flat-topped cone in the
channel between Oahu and Kauai, where we attempted to dive on our first
day but were stymied by strong winds and currents and high seas.
-Dave Clague
