Fred Magon, age 8, of Peoria, Illinois, for his question:

How are mountains made?

Mountain making is just about the biggest job in the world. Naturally it takes a long time, perhaps 100 million years or so. It also takes a lot of mighty strong energy to heave up the high mountains. So the work goes slowly. If you lived a thousand years, the slowly growing mountains would change hardly at all. But you might see some fiery volcanos and feel some earthquakes.

Scientists tell us that the real work goes on deep down in the earth's rocky crust, miles below the ground. It starts because great slabs of the crust keep moving around, very slowly. Sometimes one gets too heavy and out of balance. This upset may make the earth push up a range of mountains. Sometimes two or three great slabs bash together. This also may heave up a ridge of mighty mountains. Earthquakes help to pile up great chunks of rock. Volcanoes add more rock to the growing pile. When at last the job is done, the mountains stop growing and begin to wear down.