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Erosion A mountain has only just begun its existence when plate tectonics first thrusts it up from the earth’s interior. There is much left to be done before it looks like any mountain we might recognize. Erosion is the collection of processes by which materials are broken loose and carried away by agents like water and wind, dissecting the original upthrust rock into a myriad of peaks, ridges, valleys, and canyons. Michelangelo would hardly have been content to leave a raw block of marble parked in his living room. Instead, he had to carve the stone, releasing David from within. Erosion is the grand sculptor responsible for the sweep and curve of exalted mountain landscapes. We have seen how plate tectonics creates mountains, but other processes like erosion are simultaneously wearing them down. One of geology’s most difficult (and important) concepts is that multiple processes often operate upon a landscape at the same time. Rocks can be going up even as they are being torn down. |