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Gardens of volcanoes in the Pacific.

Like gardeners mowing a lawn half the size of California, a team of oceanographers cruised back and forth over a patch of the Pacific Ocean for two months late last year in an attempt to map the seafloor along a section of the East Pacific Rise. That sonar mapping project revealed an extraordinary number of volcanoes hidden under the waves, report Daniel S. Scheirer and Ken C. Macdonald of the University of California, Santa Barbara, and Donald W. Forsyth of Brown University in Providence, R.I. Along the patch of the rise they mapped, which ran from 15 [degrees] S to 19 [degrees] S, the scientists detected 1,113 seamounts, each of which rose at least 100 meters off the seafloor.

The East Pacific Rise marks a great rift in Earth's outer shell. As tectonic plates on the sides of the rift slowly inch apart, molten rock rises to fill the gap, creating new pieces of ocean floor. Scheirer says the volcanoes discovered along the southern part of the rise are three times more numerous than those along a well-studied part of the rise north of the equator. What's more, sonar images reveal that these volcanoes are sprouting over a broader area than those in the north. Because most of the southern East Pacific Rise remains unmapped, scientists do not know whether other patches have such widespread volcanic activity. If so, that would indicate a fundamental difference in the way the northern and southern sections of the rise evolve.
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Title Annotation:mapping of East Pacific Rise seafloor reveals evidence of many volcanoes
Author:Monastersky, Richard
Publication:Science News
Article Type:Brief Article
Date:Jun 5, 1993
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