Tuesday, March 13, 2007

Tectonic Plates and an Underwater Volcano

Because of my affection for rocks, I have closely followed the discoveries associated with Tectonic Plate Theory.  But when I moved to the Pacific Northwest, I quickly became much more aware of the jumble of plates and tectonic processes that exist here.  I am not a scientist, but try to understand what is going on under our feet.  Like geology, I enjoy history too and geology is another form of history.  In both cases I am really bad on dates.

The offshore area of the Pacific Northwest is a complex area of tectonic plates.  In this relatively small area there are many laboratories for scientists to study and understand the tectonic wonders of our planet.  We non-scientists have come to know about these wonders because of their impact on our lives.

Located approximately 300 miles west of Cannon Beach, Oregon is the Axial seamount.  It is a broad volcano about 12 by 18 miles with a summit caldera and two rift zones. Much like the Hawaiian volcanoes it is the product of a hot spot.  Over 2/3 of a mile in height, it is still nearly a mile below the surface of the ocean.

Axial, sits on the volcanic Gorda Ridge, an undersea formation that is a cousin to the Mid Atlantic Ridge.  Gorda Ridge runs somewhat parallel to the coast in a north-south direction off Southern Oregon and Northern California. Similar to the Juan de Fuca Ridge farther north off the Northern Oregon and Washington coasts, the Gorda Ridge is a spreading center where molten lava oozes onto the sea floor to form new oceanic crust.

The Juan de Fuca Plate plunges deep beneath the North American Plate and is the source of the Cascade Range of volcanoes above the subduction zone.  To the west along the boundary between the Pacific and Juan de Fuca Plates is a broad submarine mountain chain about 500 kilometers long.  This is the Juan de Fuca Ridge.  Here are a series of young volcanoes, lava flows, and hot springs in a broad valley less than 8 kilometers wide along the crest of the ridge.  At the north end of the ridge is the small platelet named the Explorer Plate and at the southern end is the Gorda Plate.

The Juan de Fuca Ridge, only about 200 miles (300 km) west of the state of Washington, is perhaps the most studied ridge with a medium spreading rate. The Juan de Fuca Ridge creates part of the Pacific plate and all of the Juan de Fuca plate.  

 The hot springs found in the valley are home to amazing creatures that scientists are fascinated with.  And for good reasons too.  One of them is a heat-loving creature capable of fixing nitrogen at a amazingly hot 198 degrees Fahrenheit.   It may be related to our Earth’s earliest organisms capable of nitrogen fixation.  These hot springs result in beautiful tall chimneys as Axial Volcano vents dense mineral hot hydrothermal fluids.  Regardless of the total darkness here, colonies of bacteria thrive as they feeding on the chemicals.  Magically, tube worms arrive as if from nowhere.


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