Keck Expedition 2004
August 18, 2004 Day 4
Courtesy of Deb Glickson, University of Washington graduate student
August 18 and 19th, 2004
The first two days of our cruise have been very successful. We arrived at
our field site, the Endeavour Segment of the Juan de Fuca Ridge, Tuesday morning
after a smooth 24-hour transit. It's about 200 miles off the coast of
Washington and Vancouver Island and is part of a linear volcanic chain, which at
the Endeavour is ~2200 m below sea level.
The first three dives were located at the Mothra hydrothermal field, the
southernmost of the five known fields at Endeavour. Our priorities
included the recovery of a microbial incubator that was in the walls of a black
smoker chimney, the collection of hydrothermal fluid and rock for microbial
studies 
,
samples for vent chemistry and biology, and geological mapping.
About half of our dive time so far has been devoted to characterizing the
geology of the southern clusters of hydrothermal chimneys at Mothra, which have
only been visited a few times. Much of the work will help to answer basic
questions about chimney abundance and types of venting at these lesser-known
sulfide clusters 
.
However, I am particularly interested in the spatial relationship between
sulfide chimneys and fissures. Mothra is a great place to study this
because there has been a lot of tectonic activity in comparison with some of the
other Endeavour vent fields, such as the Main Endeavour Field.
This summer, two earlier cruises collected high-quality seafloor images at
Mothra. We found a lot of surprising features on these maps, and used
yesterday's and today's dives to visit some of the more intriguing locations.
We followed fissures large and small, thoroughly explored the southern sulfide
clusters Cuchalainn and Stonehenge, checked out clumps of tubeworms and
bacterial mats, mapped lobate flows and collapse basins, and we came away with a
greater understanding of the processes that formed Mothra and other vent
fields.