Giant escarpment in the Indian Ocean
Surveys in the area of the Atlantic-Indian Ridge led to the discovery of the steepest submarine slope of the mid-ocean ridges. In addition, one hopes to gain new insights into the origin of simple life forms. John Madsen, a geologist from the University of Delaware, presented the results of a multi-week research cruise in the southeastern Indian Ocean at the fall 1997 meeting of the American Geophysical Union (AGU) in San Francisco. A close examination of the Southwest Indian Ridge revealed the submarine escarpment.
The Atlantic-Indian Ridge is part of the mid-ocean ridges and is located about 1600 km south-southwest of the African continent. It stretches along the boundary between the African and Antarctic plates, which are drifting apart relatively slowly - in the area of the Atlantic-Indian Ridge at about 1.7 centimeters per year. The process by which plates separate and new oceanic crust forms is called seafloor spreading. The resulting mid-ocean ridges typically exhibit active bas altic volcanism, shallow focus earthquakes, and normal faults caused by extensional forces as the plates drift apart.
Madsen is part of InterRidge, a multinational geophysical-oceanographic research team. In February and March 1996, InterRidge scientists spent 48 days aboard the research vessel Knorr, operated by the Woods Hole Oceanographic Institution. The Knorr sailed more than 10,000 nautical miles in the Indian Ocean as part of this project.
The scientists examined an area approx.1600 km south of the Cape of Good Hope. They discovered that the sea floor drops from about -150 m above sea level to about -6000 m above sea level within only 16 km. Madsen said: It is the greatest height difference that has ever been recorded at any place on earth along the mid-ocean ridges.
The generated topographic maps will help scientists to understand the physical characteristics of the sea and seabed. According to Madsen, the work done will benefit the entire oceanographic community. In addition to the geophysical and seismic findings, biological findings can also be gained through follow-up projects. "Some biologists believe that life originally arose in hydrothermal vents about 10,000 feet below the surface," Madsen said. At this depth, the ocean water is close to freezing. When a warm hydrothermal stream exits through vents into the sea and meets cold ocean water, sulfidic deposits result. From these some scientists assume that they are the key to the beginning of life on our planet. We will make maps of the seabed that will make it possible to find hydrothermal vents.
Initial findings from the surveys suggest that unusual geological activity and volcanic processes are occurring along the Atlantic-Indian Ridge. Based on the newly gained knowledge, the already existing views on the global system of mid-ocean ridges must now be examined.
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