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Deep Sea Hot Springs
| Article
# : |
19343 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
6 / 1991 |
1,743 Words |
| Author
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Robin Johnson
Robin Johnson studied physics at the Massachusetts Institute
of Technology before becoming a free-lance science and
technology writer Atlanta. |
Deep below the ocean surface, along ridges extending for thousands of miles, the earth's crust is constantly being renewed as molten rock oozes out forming new seafloor. At irregular intervals along these ridges, spectacular black plumes of hot seawater emerge from tubes projecting from the seafloor. The plumes are visible evidence of hot springs discharging into the surrounding ocean contributing to global heat loss, adding chemicals to the ocean waters, redirecting ocean currents, and dropping dissolved metals that form ore deposits. Most surprisingly, the energy and minerals released by the turbulent plumes nourish unsuspected life-forms in the murky depths--a biological community, unlike any other on earth, in that it does not depend on the sun for its primary energy source.
These striking and mysterious high-temperature hydrothermal phenomena were discovered only 12 years ago. Dubbed "black smokers" because of their color, they are among the processes that transfer heat and chemicals from the earth's interior to the sea through mid-oceanic ridges--fractures in the earth's crust running along the bottom of the oceans.
Robert Lowell, associate professor in the School of Earth and Atmospheric Sciences at Georgia Institute of Technology, has studied underwater hydrothermal systems for more than 20 years. According to Lowell, the geophysical, chemical, and biological processes associated with black smokers have global significance, and any attempts to model the long-term dynamics of the earth's environment must include black smokers as an integral component.
Mid-oceanic ridges
The mid-oceanic ridges form a vast system more than 50,000 kilometers long that extends along the floors of all the planet's oceans. These ridges demarcate the places where the semirigid plates that form the earth's outer shell are rifted apart and new crustal material is being formed. As rifting occurs, magma wells up from the partially molten region of the earth's mantle below the plates to fill the gap. As it ascends, the magma spreads and cools, forming new seafloor. This zone of magma ascent and crustal formation is subject to volcanism, earthquakes, and hydrothermal activity. The process is ongoing, so that the seafloor is widening continually and its bordering continents are drifting apart. The process creates 20 cubic kilometers of new crust every year.
As magma erupts to form new seafloor, it is cooled rapidly and fractured by contact with
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