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Name: Brenda
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Age: 18
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If the ages of Earth and Moon are nearly identical...why are most rocks found on the Moon so much older than Earth rocks?

The reason is that the moon stopped being geologically active soon after it formed, but the earth is still active. By "active," I mean that the earth is constantly recycling its minerals: rocks that have been formed erode, wash out to sea, and are carried into the earth's mantle with subducting tectonic plates, to melt and perhaps come to the surface again as lava. The age of a rock is the time since the rock solidified.

Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois

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