Tam Gallipeau, age 10, of Tucson, `Arizona, for his question:

How are rocks made?

Every rock has had. a long lifetime, chock fall of adventures. It may be  two billion or a mere million years old. An expert can examine a rock and tell its age, He can also tall same of the adventures the rack has had.

This rock, says the expert, was made by a fiery hot volcano. We will call it an igneous, or fire‑formed rock. At one time in its history it was so hot that it molted.. It poured over the earth and cooled. is it cooled it became solid rock. Pumice stone is ^n igneous rock, as is glassy black obsidian. Granite, toe, is an igneous rock. However, it is usually made way down in the underground roots of a volcano.

Another type of rock is called sedimentary. It is made from sediment or dregs. You can do a simple experiment to show how a sedimentary rock is farmed. Stir a few spoonsful of ordinary dirt into a glass jar of water. Let this muddy mixture stand a while. You will see that the dirt sinks to the bottom of the water. In time the water will evaporate and disappear. The moisture will dry out of the muddy layer. In the bottom of the jar you will have a hard layer of firmly packed dirt. It is dregs from the muddy water. All sedimentary rocks are made from muddy water. They are made by streams and rivers, lakes and seas. These rocks are usually in firm, even layers. In time those muddy 1ayers may harden into dark brown shale rocks. Slate is also a sedimentary rock. And chalk is a sedimentary rock made from tiny seashells. It was formed under the sea.

Igneous rocks are usually big irregular messes. Sedimentary rocks are usually in neat flat layers. But wind, weather end running water give these rocks no peace at all. The earth, too, works to upset them. The earth's crust heaves up to form mountains, erupts in volcanos and sinks under snows and floods. These dramatic events change the igneous and sedimentary rocks. They became metamorphic racks, which simply means changed rocks.

The weather may wear away granite, leaving tiny gains of golden sand, The sand. may become mixed with muddy clay cement and form a layer of sandstone, which is a sedimentary rock. The layer of sandstone may become buried and. pressed under now layers of rocks. The pressure turns it into hard quartzite which is a metamorphic, or changed rack. When sedimentary limestone is aged and pressed it may became marble, which is a metamorphic rock.

A solid lump of rock looks as though it has had a very dull existence. But this is not so at all. In its long life it has had many adventures and each adventure teak a long, long time.