ice or gravity. The most common sedimentary rocks are sandstones,
limestones, conglomerates and shales. Oil is found in sedimentary
formations.

3. METAMORPHIC rocks are those that have been changed from what
they were at first into something else--by heat, pressure, or
chemical action. All kinds of rocks can be changed. The result
is a new crystalline structure, the formation of new minerals,
or a change in the rock's texture. Slate was once shale. Marble
came from limestone. Gneiss (pronounced "nice") is perhaps
reworked granite.

[figure captions]

Igneous rocks are formed at high temperatures or from molten
materials. They come from deep beneath the earth. They can be
intrusive or extrusive--depending on where they cooled off.

Sedimentary rocks are formed by the action of wind, water, or
organisms. They usually are laid down on the bottom of rivers,
lakes and seas. Most of the earth's surface is covered by these
rocks. Oil is found in sedimentary formations.

Metamorphic rocks have been changed from their original state
into something else. Heat, pressure, chemical action change the
crystalline structure, the texture, even form new minerals. All
kinds of rock can be changed.


A Word On Fossils