Geology (cont. 9)


Jumping forward almost to the present, let’s look at the Batiquitos area one million years ago. This was the Pleistocene Epoch of the Cenozoic Era, and there were major climate changes. North America was in the grip of the Ice Ages. Ice sheets were sculpting the lands in the north, and valley glaciers were carving the mountains of the Sierras. (There were no glaciers in Southern California.) The Batiquitos area was now a flat, grassy plain. A stream was meandering across it on its way to the ocean. Its mouth was many hundreds of feet farther west than at present, because sea level was much lower all over the world. The ice sheets had trapped the precipitation formed from water evaporated from the oceans, thereby lowering sea level. At the coastline, the waves, much farther out than present shorelines, were cutting new terraces, which became covered by beach sands and shells, just like the beach today.


Page 9

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