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April 11th, 2003; Leg 4, Day #8

Water, water everywhere, but not a clam in sight...

Today, we have continued our search for new vent and seep sites by diving at the Tamayo fracture zone.  What is a fracture zone?  Put simply, it's a fault that connects two regions of a spreading center. For example, imagine the letter "Z."  Now imagine that the top and bottom lines are geologic spreading centers, where lava comes up and new earth is formed.  If that's the case, the middle line of the "Z" would be stretched and crushed and deformed as the upper and lower lines expand.  That's the sort of zone we are looking for on this dive.  These regions often have venting or seepage of chemically-altered fluids that have formed within the crust, and many unique organisms and communities flourish where venting and seeping fluids mix with ocean water. In the case of the Tamayo fracture zone, or TFZ, beds of clams were discovered here when scientists first visited this site years ago, and these clams are good indicators of seepage. This is what we came to find.

The scientists who first visited this site published information on where they found the TFZ and the clam beds, and we used this data to chart a course on the ocean floor that would allow us to survey as wide an area as possible.  The ship's crew and ROV pilots did a great job of "flying" over the site and allowing us to look for clam beds or other signs of venting or seepage.  We spent many hours scanning the bottom of the ocean, and did not find any obvious signs of recent seepage. Usually, we will see some clams, bacterial mat, crabs, or even tubeworms.  This time, it was water and mud but no vents or seeps.


cucumber_1.jpg (45426 bytes)Fortune, however, often favors the fool-hearty, and we came across some very interesting biology and geology that we had not anticipated.  For starters, we found some interesting rocks that may shed some light on the eruptions that have taken place here.  We collected some specimens from two different sites.  When we return to shore, geologists can use a technique called "microprobing" to examine the chemical composition of these rocks, and that will help identify their source.  We also collected some very intriguing animals.  We collected a holothuroid, or sea cucumber, that looks a bit like a small pig...at least that's what they start to look like after staring at a computer monitor for many hours (see above).  We also collected another spiny sea cucumber that's pure white and very beautiful. 

anemones_bottle.jpg (37080 bytes) We found some trash on the bottom of the sea, such as a trash bag and some kind of bottle or scoop.  Deep sea critters sometimes colonize trash, turning people's trashbag.jpg (27716 bytes) waste into little deep sea oases. Although at first glance it seems like such trash is a good thing for the bottom of the sea, providing a surface for these animals to settle on, we can be sure that if oceanic trash dumping went unregulated the oceans would be fouled in no time.  Also, we should not forget that chemicals in our waste products can be environmentally devastating in ways we have yet to understand.

wood.jpg (50313 bytes)

Sometimes nature dumps her own trash at the bottom of the sea.  We found several piece of wood wrack that were heavily colonized by all sorts of critters.  Crabs, similar to those found at vents and seep sites, were found all over one piece of wood, as were some little shrimp-like creatures that we found only under the wood.  We even collected a pink, frilly sea cucumber, one that we had never seen before, to have it identified.

pink_cucumber.jpg (55225 bytes)


When you get right down to it, ocean exploration is one part planning, two parts luck, and three parts seasickness medicine (just kidding). One thing is for sure, you never know what you're going to find.

Peter Girguis

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