Supplementary texts and extracts (for reading, discussion, translation, analysis)

To be read after Sections 1 — 3

I. Geology (introduction)

1. Geology is the science which studies the earth — its composition, its character, the architecture of its crust, and its physical history. It is sometimes defined as the science which deals with the history of the earth and its inhabitants as recorded in the rocks.¹ Many phases of the subject, however, are not primarily historical. It attempts to interpret the earth in the light of our know-ledge of chemistry, physics, astronomy and other sciences.

2. Geology includes the study of rocks and their relation to each other; the study of water and its effect upon the rocks; the study of the atmosphere, its movements, and its reactions with the mineral constituents of rocks. A geologist is called upon not only to classify minerals and rocks but to locate valuable mineral deposits and to direct their exploration, and to give counsel (advice) regarding dam sites, tunnels, irrigation systems, control of floods, and other engineering projects.

3. The earth is continually changing. Some changes are great and rapid while others are small and slow although they are nevertheless effective. The geologist seeks to analyze the changes and the processes that cause them. He assumes that these processes have been operative during the past as well as² in the present, although perhaps with different intensities, and he seeks to explain the present earth as the result of processes which have been acting through long ages of time. Thus the present, which is the outgrowth of the past, is also the key to the history of the past.

4. The science of geology commonly is divided into several branches, each of which emphasizes certain phases of the subject. Cosmology deals with the early history of the earth and the relations of the earth to other heavenly bodies in the universe, such as the sun, the other planets and other stars. Petrology treats of the rocks of the earth. Structural geology deals with the arrangements or the structural relations of rocks and particularly with their relations to each other. Dynamic geology treats of the forces and the movements that have affected the rocks and the results of these movements.

Physiography deals with the development of the form or contour of the surface of the earth and the origin of the mountains, valleys and plains. Paleonto-logy is the study of the remains of ancient life that are found in the rocks. Historical geology is the study of the history of the earth as shown by its rocks and particularly the record of events that is revealed in the rocks and by the relations of the rock formations to each other. Economic geology treats of the occurrence, origin, and distribution of the materials of the earth that are valuable to man. It includes the study of deposits of the metals, coal, petroleum, and many other substances. All of these branches of geology are closely related to each other and form part of the general subject of geology.

Notes

¹ as recorded in the rocks — как она (история) зарегистрирована в породах

² as well as — a также (и)