Elementary Geology

The mine finder needs to understand the physical and chemical process that make the Earth produce its mineral wealth. For example, understanding plate tectonics – the mechanism behind continental drifts – allows geologist to locate areas of plate collision where seismic and geologic activity can form mineral deposits.

Earth is very old indeed; the oldest known rocks date back nearly four billion years. And geological processes move slowly; a mountain range thousands of meters high is lifted at a rate of a few centimeters per year. Erosion wears away such a mountain range just as slowly.

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

The most recent opening started about 200 million years ago and is still going on. A more recent orogeny created the mountain ranges on the cost of North America.