Unit VII

LAND FORMS

Reading Material Text a

Task

1. Before reading the passage discuss these points with a partner.

   • Into how many parts is the earth’s surface divided?

   • How are land and sea distributed?

2. Now read the text, translate it and get ready to do the exercises after the text. Land Forms of the Earth

The earth's surface has traditionally been divided into two parts: ocean basins and the continents which rise above them. Land and sea are very unevenly distributed: the earth can be divided into two hemispheres – one contains four fifths of all the land and the other is nearly nine-tenths covered by water. Nearly three-fourths of all the land surface is underlain by marine rocks. Fossils of marine animals in the rocks of high mountains and inland deserts prove that even many of the continental heartlands were at one time or another drowned beneath the sea.

The World's Main Land Masses. – Most of the land area of the world is located in the Northern Hemisphere. Eurasia and North America, although now separated by Bering Strait, were once a single land mass. All other large land areas, except Antarctica and Australia, are joined to these great land masses. Africa and South America are united with Eurasia and North America, respectively, by narrow necks of land called isthmuses.

Continents. – The great land masses are called continents. Most of them are triangular in shape, pointing toward the south. Tongues of land that extend from continents into bodies of water are called peninsulas. Continents do not end abruptly at the shore of the ocean. In many cases, there is a large area offshore where the ocean water is quite shallow. The land under such shallow water is called a continental shelf. The continental shelves are the submerged edges of the continents. Off most coastlines the bottom slopes gradually (gently) form the shore seaward before passing into a much steeper continental slope. The continental shelf varies greatly in width along different parts of its extent.

Islands. – An island is a body of land entirely surrounded by water. Many islands are submerged mountain ranges. Some, notably in the Pacific Ocean, were created by volcanic action. Volcanoes can be built up beneath the sea until they emerge and become islands. Certain islands are composed of coral.

Mountains. – An elevation above the surface of the earth with a small summit (top) area is called a hill or a mountain. A hill is not so lofty as a mountain and has gentler slopes. Mountain slopes are steeper. Mountains are said to be "old" or "young" according to the length of geologic time that they have been in existence. Old mountains have been acted on by the forces of erosion for so many years that their profiles are smoothed and rounded. Young mountains are jagged in outline and have a rugged relief.

Plateaus. – A plateau is an elevation, which has a large surface area. Some plateaus, like the Plateau of Tibet, are raised far above sea level.

Plains. – Plains are areas of level land. According to location or origin there are several types of plains, each with its own typical characteristics:

1. Coastal plains lying along the shore of the ocean.

2. Interior plains lying in the heart of a continent.

3. Glaciated plains formed by the great glaciers.

4. Flood-plains formed from the alluvium deposited by rivers.