I. Answer the following questions:

1. What kinds of changes are taking place in the earth's crust?

2. What is denudation?

3. What are the chief agents of denudation?

4. How does the sun affect the rocks?

5. When do rocks expand? contract?

6. What causes cracks in the rocks?

7. In what way does wind affect the rocks?

8. What is the action of the wind?

9. What does rain*water absorb from the air?

10. What is the chief agent of denudation in hot countries?

11. What causes the cracks to widen?

12. What happens with rain-water when it falls on to the ground?

13. What is the action of streams?

14. What causes the narrow valleys to become broader?

15. What increases the force of the water?

16. What are glaciers?

II. Find in the text equivalents to:

to understand, all the time, chief, to eat away, broad, to become, much, strong, to continue.

III. Translate into Russian paying attention to the translation of some verbs with different prepositions:

1. Rivers carry a load of sand and mud.

2. They carry on their work under hard conditions.

3. The rivers carry along stones and sand.

4. The wind loosens and carries away the soil.

5. Along the seashore the wind usually blows from the water toward the land during the day and from land toward water during the night.

6. The wind blows away rock particles and rolls them along the surface of the earth.

7. When wind blows up the side of a mountain, it cools 3 degrees F. for every 1000 feet that it climbs.

8. The wind picks up sand and blows it against all uplifted surfaces.

TEXT 6

Materials of the lithosphere. Rocks

We know very little about the materials of the whole lithosphere through direct observation. It is true that man has studied very intensively the rocks and minerals which are available to him, but these constitute only a small fraction of all the materials of the earth. Scientists have secured specimens from the slopes of Mount Everest at an elevation of more than 27,000 feet which prove that the mountain was once beneath the sea. One can study the materials on the walls of the great canyon or the deepest mines in the world. Several well borings for oil have reached depths of from 12,000 to more than 15,000 feet, and through examination of the drill cuttings, one can determine the nature of the rocks at any depth in the hole. However, all rock exposures so far available to man are small compared with the 4,000-mile radius of the earth.

The word lithosphere really means rock sphere. Rocks, then, constitute most of the solid material of the earth. One can divide rocks into three great groups: igneous, rocks, sedimentary rocks and metamorphic rocks. Nearly all rocks contain two or more minerals.

Igneous rocks. – Igneous rocks are those resulting from the interior heat of the earth. There are two main kinds: 1) those which reach the surface in volcanoes, 2) and those which moved underground but became solid before they reached the surface.

Sedimentary rocks. – During the long periods of geologic time, igneous rocks have undergone erosion. The forces of erosion carried away particles of eroded rock and set them down in layers either on dry land or under water. As a result, this material changed into another type of solid material known as sedimentary rock.

Metamorphic rocks. – As a result of heat, pressure and movement, igneous and sedimentary rocks changed their original qualities in some way forming a new material called metamorphic rocks. The metamorphic rocks are generally crystalline and harder than the original material.

Notes

as a result of smth. – в результате чего-либо

so far – пока

WORDS

observation наблюдение

true верный, правильный,

настоящий

intensive интенсивный

mineral минерал, полезные

ископаемые

available имеющийся (в распоряжении)

to constitute составлять

fraction часть, частица, доля

to secure достать, добыть, обеспечить

specimen образец, экземпляр

canyon ущелье, каньон

mine шахта

well boring буровая скважина

oil нефть

to reach достигать

drill cutting образец («с долота»)

to determine определять

nature природа, характер

hole отверстие, скважина

exposure выход на поверхность

to compare сравнивать

radius радиус

igneous изверженный

sedimentary осадочный

to result from проистекать, происходить,

в результате

volcano вулкан

geologic геологический

to undergo подвергаться, испытывать

to erode размывать, выветривать

erosion эрозия

original первоначальный

quality качество

crystalline прозрачный, кристаллический