3) The relief. Rivers and lakes. Mineral resources. Climate of the usa.

Relief.

The relief of the country isn’t so complicated as that of Europe but it is more varied than that of Africa. If you look at the map you will see that there is a distinct contrast between the elevated Western part of the continent and the lower Eastern part. The mainland of the USA present 4 physical divisions - 2 elevated parts, and 2 lowland parts. The uplift in the Eastern part is the Appalachian mountains. They are rather old and less extensive than the mountains in the West, they’re much denuded and worn down. They do not rise higher than 200 meters above the sea level. They consist mostly of mountain ranges that run parallel with the Atlantic coast.The 2nd uplift is in the West . It is the Cordilleras system from Mexico into the Arctic region. The 1st subdivision of the C. is made up by the majestic Rockies. These mountains are as old as the Alps in Europe. Their peaks reach an altitude of 5.600 meters, but the highest mountain peak is in Alaska. It is McKinley (6193m). The Rockies are covered by perennial snow, powerful glaciers move slowly down the slopes to the valleys where they melt and reach the sea in places. There’s much volcanic activity in the Rockies. Large areas are covered with hardened lava and powerful geysers throw up fountains of hot water at regular intervals. All this shows that the Rockies are still in the process of formation. West of the Rockies there is a region made up of the material washed down from the Rockies.

There is a cascade mountain made up of the melted rock of the Rockies.

Close to the region there is a particularly lowly place, a stretch of desert. Pioneers named it Death Valley. Actually it is an ancient lakebed, 280 m below the sea level. Americans named this place the bottom of the USA, being the lowest spot.

For 140 miles, scarcely a bush can be seen. In the area between Salt Lake City and Reno, the capital of Nevada, there is nothing but dead lakes, dry rivers, small animal life, but enormous mineral wealth together with the inhuman beauty of the desert. The 3^rd subdivision of the C. is the Sierra-Nevada range and cascade mountains. They extend from Canada in the North and southward to the Mexican border.

This area is almost as high and rugged as the Rockies. They form almost an unbroken wall between the inland USA and the Pacific Coast. There is only one easy route at the point where the Columbia River cuts through the Mountains in a wide pass. The Region is not suited for growing crops, but there are great forests in the cascade and large gold deposits in Sierra-Nevadas.

At the very edge of the Pacific coast there are coastal ranges.

Lowlands.

The heart of the USA is a vast plain which extends from Central Canada to the Gulf of Mexico., and from the Appalachians to the C.-s. The eastern portion of the plain is called the Central Plains, and the western one – the Great Plains. Both of them are good-soiled. The central plains are also called the Mississippi Valley because the greater part of it comprises the drainage area of the Mississippi river. This place is a vast grassy, almost treeless area called prairies. The northern part of the Central plains is made up by the Great Lakes Plain. Along the Pacific coast there is a narrow strip of lowland, wider in the south and narrower in the north. This is the area of numerous farmlands. There is also much lowland on the Atlantic coast. This is the place where the 1^st settlers from Europe came.

Rivers and Lakes.

The USA has thousands of streams. The Mississippi is one of the world’s greatest drainage rivers. It gathers its waters from 40 per cent of the US territory. It starts in the Rockies and runs 4000 miles into the Gulf of Mexico. One its pop names is the “Fathers of Waters”. Together with its two tributaries, the Missouri, and the Ohio river, the Mississippi becomes of incomprehensible dimensions. Missouri is the “Great Muddy”.

The Gulf of Mexico area is drained by the number of short rivers from 400 to 900 miles long except the Rio-Grande river that forms the part of the border with Mexico. The river is 2870 km long. There are great river systems in the West. They all carry waters into the Pacific f.e. Columbia river and its chief trib., the Snake river. Then there is the Colorado river in the south, which cuts through the Grand Canyon.

The Sacramento river and its tributaries. The three river systems in the West have great values as sources of water power. There is a large area in the western part of the USA, called the Great Basin, which has no surface drainage to the sea. This is a desert, its rivers seem to go nowhere. The region is so dry that the rivers evaporate or sink into the sand. Most of the time they are simply dry beds. But after the sudden desert storms the rivers become savage torrents, irresistible and dangerous.

Lakes.

The USA has different lakes of different sizes and kinds. The Great Lakes make up for the largest group of lakes in the country. They are Superior, Michigan, Huron, Erie, Ontario. Only lake Michigan lies entirely within the USA borders. All the others make a natural border between the USA and Canada. Lake Superior is the largest freshwater lake in the world. It is 80000 sq. km. Lakes Erie and Ontario are connected by the famous Niagara river. It is 1km wide. It throws its waters over a ledge of 50m.

And forms the famous Niagara falls, which are a great attraction. The great lakes are connected with the Atlantic by the St Lawrence river. Along the Gulf of Mexico coast there are hundreds of lakes lagoons and swamps. West of the Rockies there is one more group of lakes – some of them high in the mountains, in crater pits. Some are deep and some are shallow. The most famous of them is the Great Salt lake in Utah. And also the Salton Sea. This sea is 240 feet below sea level in South California.

Mineral resources.

The country possesses vast natural resources. The major is iron. 3\4 of it come from the Great Lakes district, especially from the Lake Superior region. There are large deposits of iron ore in the Appalachians. On the Western slopes of the Mountains there are deposits of coal. The Cordilleras are rich in gold and copper, uranium, metallic ores. North of the Gulf of mexico and on the Pacific coast there are large deposits of gas and oil. Texas an California are the most important mineral-producing areas. Some kinds of mineral resources such as coal, sulphur, phosphorus, as well as oil, are extracted in excess, some others f.e. copper, zinc, iron ore gas, are not enough to meet the demand of the country’s economy. There is very little or none at all of such kinds of resources as nickel, tin, chromium, and manganese ores. For these minerals the USA entirely depends on import. The USA policy towards the import and excavation of its own mineral resources may be called peculiar and even far-sighted. They import not only the resources they are short of, but also the ones they have in plenty, such as oil, coal, copper. Other countries sell, they store.

Recently large deposits of gas and oil have been discovered in Alaska.

Climate.

In no part of the world are the Arctic and the tropical waters so close to each other as in the USA. The absence of mountains in the North allows cold winds from the Arctic region to penetrate far inland causing frost and snowing winter as far south as the gulf of Mexico. ON the other hand, the absence of mountains on the south permits the tropical winds to travel far north. The weather in the country is therefore very unstable with frequent changes of temperature especially in winter. Besides there sometimes occur cyclones in summer and autumn called tornadoes in the USA. They sweep away everything in their path, uprooting trees, killing people. The influence of the great warm ocean currents is not so strong in the USA as in Europe. On the whole the climate in the USA is more rigorous than in Europe on the same latitude. Virtually every type of climate can be found in the USA from Arctic in Alaska to subtropical in Florida. The average temperatures in July are 16-26 in the East , 32 S, 14-16 West. The January is -24 in Alaska, -18 in the Centre, +20 Florida. The lowest -60 Alaska, highest +56 in Death Valley.

The Northern part of the Pacific coast receives much rain. The sky is usually overcast, sunny days are rare. It is called the kingdom of everlasting autumn. Winters are not very cold, summers are not very hot. The climate is of maritime type.

Especially dry is the climate on the platoes between Colorado ranges. There are sharp differences between day and night temperatures. The sky is usually cloudless. The annual rainfall is barely 200mm. This is the desert type of climate.

The pacific coast of the California peninsula enjoys a subtropical climate. So does the region of the Gulf of Mexico. The climate here is of the Mediterranean type. Rainfall is small, most of it falls in winter. Summers are dry, hot and long. Most of the climate has humid continental climate with hot summers and cold winters