According to the generally accepted theory of plate tectonics, the earth’s crust consists of a dozen or so plates of solid rock moving across the mantle—the slightly fluid layer of rock between crust and core. Most earthquakes can then be explained as a result of the grinding of these plates against one answer—how can often intense subduction take place at certain locations with little or no seismic effect?
One group of scientists now proposes that the relative quiet of these zones is tied to the nature of the collision between the plates. In many seismic hot zones, the plates exhibit motion in opposite directions—that is, they collide because they are moving toward each other. And because the two plates are two sheets of sandpaper pressed together, these plates offer each other a great deal of resistance.
This proposal also provides a warning. It suggests that regions that were previously thought to be seismically innocuous—regions with low levels of subduction—may in fact be at a significant risk nature of the subduction taking place.
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