Taсдиқлайман” “Чет тиллар” кaфедраси мудири

III. Translate and make short summary of the text.

Text THE NATURE OF ROCKS

To the geologist, rock is the natural, solid material that makes up the earth. The first word, natural, immediately eliminates man-made materials like cement, glass, brick, and steel, even though these all come from the crust of the earth.

The second word, solid, rules out the air and other gases, the oceans, rivers, lakes, and other liquids.

However, solids can be changed to liquids and gases by being heated; liquids and gases can be changed into solid by being cooled.

The definition of a rock means solid at temperatures which normally occur in the earth's crust.

Even this does not cov­er everything, because one of the most common chemical compounds on the surface of the earth may or may not be rock, depending on its temperature.

This chemical com­pound is water — H2O.

Water makes up nearly three fourths of the surface of the earth.

Most of it is in the form of a liquid, and while liquid water affects the rocks of the earth in many ways, water is not a rock.

However in the arctic and Antarctic regions, and in the temperate regions during winter, millions upon millions of tons of water are a hard, frozen solid.

In the Antarctic, ice occurs in layers nearly two miles thick.

Ice is, therefore, a rock, and geologists study the great ice fields just as they study other rock for­mations.

In speaking of rocks, geologists use the word solid in its technical sense.

A solid is the matter that is not a liquid or gas.

What the geologists would sometimes call solid rock might seem strange to you.

The wet sands on the beach and the shifting sands in the desert are a solid and a rock.

This is also true of the layers of mud and muck in the swamps, or the ash and cinders from volcanoes. They are rock also.