IN THEIR QUEST FOR KNOWLEDGE, SCIENTISTS WILL take advantage of anything that's helpful, even a nuclear blast. Studies of the shock waves given off by a Chinese .66-megaton nuclear test have revealed a "continent" 2,000 miles underground, at the boundary between the molten iron of the planet's core and the molten rock just above it. The word continent is used loosely; what two scientists at the U.S. Geological Survey found was a region 200 miles across and 80 miles deep that is denser than surrounding regions. The implication: the core-mantle boundary may be as complex as the earth's surface.
When the...
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