Elementary Geology

A person looking for mines needs to comprehend the chemical and physical processes that cause the earth to produce its mineral riches. For instance, comprehending plate tectonics – the mechanism behind continental drift - permits the geologist to find areas of plate collision where seismic and geologic activity can form deposits of minerals.

The fact of the matter is that the world is very old indeed; the oldest rocks known to man can be dated back to at least four billion years, and the processes of geology move very slowly; a mountain range which is thousands of meters high is lifted at a rate of a few centimeters every year. Erosion wears away such a mountain range at basically the same slow speed.

In most parts of the world, there have been not only one but many such cycles of uplift and erosion. Time periods of mountain-building are referred to as orogenies. The east coast of North America, for instance, has undergone at least three distinct periods of mountain-building, each one corresponding with the closing and opening of the Atlantic Ocean.

What started 200 million years ago is the most recent opening and is still occurring nowadays. A more recent orogeny was what created the mountain ranges on the west coast of North