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 water_sample.jpg (104493 bytes), 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 smoker.jpg (117295 bytes).  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. 

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