David Griffith, age 10, of Montgomery, Ala., for his question:

ARE EARTHQUAKES EXPLOSIONS?

Sometimes an earthquake makes a noise like thunder or rolling drums. Sometimes it sounds like a big explosion. Naturally it does not create thunder and nobody beats the drums. And so far as we know it is not an explosion down there in the earth. Scientists tell us that an earthquake happens when great chunks of rock are shifted around underground. Sometimes it makes deep cracks on the surface.

In some parts of the world there are weak spots in the earth's crust. These are earthquake zones, where two slabs of the crust rub against each other. Often they are inching along in different directions and the two edges cling together until the last minute. Then suddenly they spring apart. This is what sets off all the shivering and shaking. Massive slabs are shifting around underground. And sometimes the underground upheaval sounds like explosions and thundering drums.