Most of us are familiar with "Old Faithful"
in Yellowstone National Park. This famous geyser erupts several times a day. It spouts a column of water heated
by volcanic rock deep within the Earth's crust.
A hydrothermal vent is a geyser on the seafloor. It continuously spews super-hot, mineral-rich water
that helps support a diverse community of organisms. Although most of the deep sea is sparsely populated, vent
sites teem with a fascinating array of life. Tubeworms and huge clams are the most distinctive inhabitants of Pacific
Ocean vent sites, while eyeless shrimp are found only at vents in the Atlantic Ocean.
The first hydrothermal vent was discovered in 1977. They are known to exist in the Pacific and Atlantic oceans.
Most are found at an average depth of about 2,100 meters (7,000 ft) in areas of seafloor spreading along the Mid-Ocean
Ridge system- the underwater mountain chain that snakes its way around the globe.
How do hydrothermal vents form? In some areas along the Mid-Ocean Ridge, the gigantic plates that form the Earth's
crust are moving apart, creating cracks and crevices in the ocean floor. Seawater seeps into these openings and
is heated by the molten rock, or magma, that lies beneath the Earth's crust. As the water is heated, it rises and
seeks a path back out into the ocean through an opening in the seafloor.
As the vent water bursts out into the ocean, its temperature may be as high as 400°C (750°F). Yet this
water does not boil because it is under so much pressure from the tremendous weight of the ocean above. When the
pressure on a liquid is increased, its boiling point goes up.
Chimneys top some hydrothermal vents. These smokestacks are formed from dissolved metals that precipitate out
(form into particles) when the super-hot vent water meets the surrounding deep ocean water, which is only a few
degrees above freezing.
So-called "black smokers" are the hottest of the vents. They spew mostly iron and sulfide, which combine to
form iron monosulfide. This compound gives the smoker its black color.
"White smokers" release water that is cooler than their cousins' and often contains compounds of barium, calcium,
and silicon, which are white.
Geologists are intrigued by how rapidly vent chimneys grow - up to 9 meters (30 ft) in 18 months. A scientist
at the University of Washington has been monitoring the growth of "Godzilla," a vent chimney in the Pacific Ocean
off the coast of Oregon. It reached the height of a 15-story building before it toppled. It is now actively rebuilding.
There are many other reasons why scientists want to learn more about hydrothermal vents. These underwater geysers
are believed to play an important role in the ocean's temperature, chemistry, and circulation patterns.
Scientists also are fascinated by the unusual life that inhabits vent sites. These creatures who live in darkness,
from bacteria to tubeworms, may light the way to the development of new drugs, industrial processes, and other
products useful to us all.