from GeologyAbout Website
That's what a 2003 research expedition
found in the Gulf of Mexico on a seafloor hill the scientists named
Chapopote, the Mexican Spanish name
for tar. It's the world's first known asphalt volcano. There are
more being found all the time.
As is common around the Gulf, oil and
gas leak upward with the salt.
Even with this short-range visual instrument they documented one square kilometer of tar flows, some of them 20 meters across. Besides asphalt, the expedition found places soaked with petroleum and others with cold, white layers of methane hydrate.
cold seeps elsewhere on the world's
seafloor, all of these localities supported colonies of
chemical-eating organisms. Bunches of tubeworms were found growing
in and around the tar flows. Apparently something makes the asphalt
attractive to life, but no one is sure yet how the biogeochemistry
In fact it forms asphalt "aa" and "pahoehoe" just like what you find in Hawaiian basalt. In another parallel with ordinary volcanoes, the warm asphalt turns delicate icy layers of methane hydrate into bursts of free gas, just as hot rock lava causes explosions by flashing groundwater into steam - phreatomagmatic eruptions.
(But I don't know what you'd call a
tar/hydrate eruption in scientific Latin.)
Examining samples from the tar flows,
the researchers found abundant small pores lined with various
minerals: sulfates, chlorides and carbonates. They theorized, in the
18 October 2005 Eos, that the energy source involves a special
substance: supercritical water.
As the water cools and the dissolved
load precipitates, a shell of tar would form protecting the hot
fluid inside, analogous to lava tubes, and the fluid would
eventually reach the sea floor. There the more volatile parts of the
"lava" would enter the seawater while the heavy asphalt remains.
Are There More
In fact MacDonald, in the 14 May 2004
Science, pointed out that tar flows had been photographed 200 km to
the north of Chapopote in 1971. He suggested that others might
locate more occurrences by doing what his team did: looking for oil
slicks in satellite images of the sea surface.