The difference in composition between the continents and the sea floor on earth is due to plate tectonics. Granite tends to “float” a little more than basalt, so as the crust gets recycled the granite stays on top and forms continents. On mars the whole planet is basaltic, which is more evidence that if there was plate tectonics, it didn’t last long, since it never managed to separate out granitic rocks from basaltic.
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2016年09月28日 (水) 22時24分22秒 ( 231 )