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Underwater Asphalt Volcanoes Discovered by UC Santa Barbara Scientists
SANTA BARBARA, Calif., Apr 26, 2010 (ASCRIBE NEWS via COMTEX) --
About
10 miles off the Santa Barbara coast, at the bottom of the
Santa Barbara Channel, a series of impressive landmarks rise
from the sea floor. They've been there for about 40,000
years, but they've remained hidden in the murky depths of
the Pacific Ocean - until now.
UC Santa Barbara scientists, working with colleagues from
Woods Hole Oceanographic Institution (WHOI), UC Davis,
University of Sydney, and University of Rhode Island, say
that they have identified a series of asphalt volcanoes on
the floor of the Santa Barbara Channel. The largest of these
undersea Ice Age domes is at a depth of 700 feet (220
meters) - much too deep for scuba diving - which explains
why the volcanoes have never been spotted by humans.
"It's larger than a football field long and as tall as a
six-story building," said David Valentine, professor of
earth science at UCSB and the lead author of a National
Science Foundation-funded study published online this week
in the journal Nature Geoscience. "It's a massive feature,
completely made out of asphalt."
Chris Reddy, director of the Coastal Ocean Institute at
WHOI and a co-author of the study, has studied oil spills
his whole career. "These volcanoes are an astonishing
display of nature," Reddy said. "And they underscore one
little-known fact: Half of the oil that enters the coastal
environment is from natural oil seeps like the ones off the
coast of California."
Valentine, Reddy, and their colleagues first viewed the
volcanoes during a 2007 dive on the research submarine
Alvin, though Valentine credits Ed Keller, professor of
earth science at UCSB, with guiding them to the site. "Ed
had looked at some bathymetry (sea floor topography) studies
conducted in the 1990's and noted some very unusual
features," Valentine said.
Based on Keller's research, Valentine and other
scientists took Alvin into the area in 2007 and located the
mystery features. Using the sub's robotic arm, the
researchers broke off samples and brought them to labs at
UCSB and WHOI for testing. In 2009, Valentine and colleagues
made two more dives to the area in Alvin and also did a
detailed survey of the area using an autonomous underwater
vehicle, Sentry, which takes photos as it glides about nine
feet above the ocean floor.
"When you fly Sentry over the sea floor, you can see all
of the cracking of the asphalt and flow features," Valentine
said. "You can see all of the textures of a flowing liquid
that solidified in place. That's one of the reasons we're
calling them volcanoes, because they have so many features
that are indicative of a lava flow."
But tests showed that these aren't your typical lava
volcanoes found in Hawaii and elsewhere around the Pacific
Rim. Using a mass spectrometer, carbon dating, microscopic
fossils, and comprehensive, two-dimensional gas
chromatography, the scientists determined that these are
asphalt and were formed when petroleum was flowing from the
floor of the channel about 30,000-40,000 years ago.
The researchers also determined that the volcanoes were
at one time a prolific source of methane, a greenhouse
gas. The two largest volcanoes are about a kilometer apart
and have pits or depressions surrounding them. These pits,
according to Valentine, are signs of "methane gas bubbling
from the subsurface." That's not surprising, Valentine said,
considering how much petroleum was flowing. "They were
spewing out a lot of petroleum, but also lots of natural
gas," he said, "which you tend to get when you have
petroleum seepage in this area."
The discovery that vast amounts of methane once emanated
from the volcanoes caused the scientists to wonder if there
might have been an environmental impact on the area during
the Ice Age. Valentine found two high-profile studies, one
in the journal Science and the other in the Proceedings of
the National Academy of Sciences, which examined events from
that time, including a period in which water in the channel
became anoxic. "It became a dead zone," Valentine
said. "We're hypothesizing that these features may have been
a major contributor to those events."
While the volcanoes have been dormant for thousands of
years, the 2009 Alvin dive revealed a few spots where gas
was still bubbling. "We think it's residual gas," said
Valentine, who added that the amount of gas is so small that
it is harmless because it never reaches the surface.
Other co-authors of this study are Christopher Farwell,
Sarah C. Bagby, Brian A. Clark, and Morgan Soloway, all from
UCSB; Robert K. Nelson, Dana Yoerger, and Richard Camilli,
from WHOI; Tessa M. Hill, UC Davis; Oscar Pizarro,
University of Sydney; and Christopher N. Roman, University
of Rhode Island.
- - - -
CONTACTS: George Foulsham, UCSB Media Relations,
805-893-3071 george.foulsham@ia.ucsb.edu
David Valentine, 805-893-2973, valentine@geol.ucsb.edu
Chris Reddy, creddy@whoi.edu
NOTE TO EDITORS: For downloadable photos, go to
http://www.ia.ucsb.edu/pa/display.aspx?pkey=2228 . For a
video, go to the UCSB News & Research Facebook page at:
http://www.facebook.com/pages/Goleta-CA/UC-Santa-Barbara-News-Research/2
38559203390
.
((AScribe - The Public Interest Newswire / http://www.ascribe.org))
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