9. Landscape. Major rivers, lakes and waterfalls in the United States.

The U.S.A. is divided into three areas: Eastern area — high­land with the Appalachian Mountains, Central area — plain, and Western mountainous area including the Cordilleras and the Rocky Mountains. Between the mountain ranges are the central lowlands, called the prairie, and the Eastern Lowlands, called the Mississippi Valley. The geography of the United States is extremely diverse. The Rocky Mountains in the West can reach over 14,440 feet (4,401 meters) high, but the land of the Great Plains stretches flat for hundreds of miles. Large reserves of coal, oil, gas, iron ores, ferrous and non-ferrous metals form a solid base for the development of the U.S.A. industry.

The north-eastern part of the U.S.A. is the region of the five Great Lakes — Lake Superior, Huron, Michigan, Erie and Ontario. The largest is Superior. The lakes are joined together by short rivers and ca­nals and cut by rapids. The greatest of these rapids is the Nia­gara Falls. It is one of the largest waterfalls in the world. The waters of the five lakes have the outlet into the Atlantic Ocean by the St. Lawrence River. In the west of the U.S.A. there is another lake called the Great Salt Lake.

The greatest rivers of the U.S.A. are the Colorado and the Columbia flowing into the Pacific Ocean, the Mississippi with its tributaries — the Missouri and the Ohio — flowing into the Gulf of Mexico, and the Hudson river, which flows into the Atlantic Ocean. The rivers in the west are unsuitable for navi­gation as they are cut by deep rapids. They serve as a great source of electric power.

10. Climate. Plant and animal life.

There are different climatic zones on the territory of the U.S.A. On the whole the climate of the country is conti­nental and mostly temperate but it varies from tropical in Hawaii to arctic in Alaska. There are places that are warm all the year round, and there are places covered with ice and snow where summer never comes. The greatest part of the territory of the US is situated between 30° and 49° North Latitude.

Generally the western and southern half of the USA has an overall warmer weather, as compared to the eastern and northern half. The Eastern/Northern half is extremely cold in winters accompanied by heavy snowfall, and has pleasant summers, whereas the Western/Southern part has extremely hot summers and comparatively tolerable winters.

All four of the world’s most productive agricultural climates are found in the United States. These climatic regions display a favorable mix of rain and sun as well as a long growing season, and together, they cover more than a third of the country. Favorable climates have allowed farmers to produce vast quantities of grain for human consumption and crops to feed animals.

The dominant features of the vegetation are indicated by the terms forest, grassland, desert, and alpine tundra. A coniferous forest extends interruptedly in a narrow strip near the Canadian border from Maine to Minnesota and southward along the Appalachian Mountains. Southward, a transition zone of mixed conifers and deciduous trees gives way to a hardwood forest of broad-leaved trees. This forest, with varying mixtures of maple, oak, ash, walnut, hickory, sycamore, beech, and the more southerly tulip tree, once extended from New England to Missouri and eastern Texas. The grasslands occur principally in the Great Plains area and extend westward in to the Rocky Mountains. The alpine tundra consists principally of small plants that bloom brilliantly for a short season. The desert, extending from southeastern California to Texas, is noted for the many species of cactus, some of which grow to the height of trees, and for the Joshua tree and other yuccas, creosote bush, mesquite, and acacias.

The animal geography of the United States is far from a natural pattern. First, many species were hunted to extinction or near extinction, most conspicuously, perhaps, the American bison, which ranged by the millions nearly from coast to coast but now rarely lives outside of zoos and wildlife preserves. Second, habitats were upset or destroyed throughout most of the country — forests cut, grasslands plowed and overgrazed, and migration paths interrupted by fences, railroads, and highways. Third, certain introduced species found hospitable niches and, like the English sparrow, spread over huge areas, often preempting the habitats of native animals. Fourth, chemical biocides such as DDT were used for so long and in such volume that they are believed at least partly responsible for catastrophic mortality rates among large mammals and birds, especially predators high on the food chain. Fifth, there has been a gradual northward migration of certain tropical and subtropical insects, birds, and mammals, perhaps encouraged by gradual climatic warming. In consequence, many native animals have been reduced to tiny fractions of their former ranges or exterminated completely, while other animals, both native and introduced, have found the new anthropocentric environment well suited to their needs, with explosive effects on their populations. The coyote, opossum, armadillo, and several species of deer are among the animals that now occupy much larger ranges than they once did.