Chapter 1 Geography

I Geographical Features

The United States is located in the central part of North America, bordering the North Atlantic Ocean in the east and the North Pacific Ocean in the west. With a total area of 9, 372,615 square kilometers, the United States ranks the fourth largest country in area in the world, after Russia, Canada and China.

As far as geographical features are concerned, the country can be separated into three major divisions: the highlands in the east, the mountains in the west, and a vast plain region in between. In order to explain more clearly, we can begin by dividing the continent of North America into 7 regions. These regions are large areas where the landforms（地貌）or kinds of lands are similar. The 7 regions are:

●the Atlantic and Gulf coastal plain

●the Appalachian Mountains

●the Central Lowlands and the Great Plains

●the Rocky Mountains

●the Great Basin（山间高原盆地）

●the Pacific Coastal Ranges and Lowlands

●the Canadian Shield（also called the Laurentian Shield，加拿大地盾，劳伦地盾）

The Coastal Plain

Along the east coast of North America is a narrow plain. This plain begins far up the coast and becomes wider as you travel south. The coastal plain extends all along the Atlantic and Gulf coasts of the United States. The coastal plain is low and flat. In some places, there are large areas where the land is covered with shallow water. These areas are called swamps or wet lands. The swamps are thick with plants, and there are many wild animals.

The Appalachian Mountains

In the west of the coastal plain are the Appalachian Mountains. The Appalachians are a chain of thickly wooded mountains that stretch from Maine all the way to Georgia and Alabama. The topography（地形学）of these mountains is different, and not many of them are nearly as tall as west-coast ranges. Much cultivation and urbanization has occurred in the Appalachians, but there are still many remote areas. The Appalachian Mountains are different from other ranges because most of their trees are deciduous（每年落叶的）.

The Appalachians are old mountains. This means that they were formed millions of years ago. Since then, they have been worn down by the wind and the weather. Today, most of these mountains have rounded tops. The highest peak of the Appalachians is only a little over 2,000 meters. The valleys between them do not have steep sides. In parts of the Appalachians, the land is not good for farming. People have farmed thin strips of land in the valleys where it is flat. But farmers here barely grow enough for themselves to eat. Much coal is found in these mountains.

The Great Plains

In the west of the Appalachians, the land drops to the mighty Mississippi River. Still west is a vast open area called the Great Plains. The Great Plains is the broad expanse of prairie which lies east of the Rocky Mountains in the United States of America and Canada. As one of the largest areas of flatland in the world, it stretches from northern Canada to the Gulf of Mexico, covering the US states of New Mexico, Texas, Oklahoma, Colorado, Kansas, Nebraska, Wyoming, Montana, South Dakota and North Dakota, the Canadian provinces of Saskatchewan and Alberta. Much of Minnesota and Iowa and much of the Canadian province of Manitoba also lie in the Great Plains. It is usually divided by Missouri River into two regions: the Central Lowland in the east, and Great Plains in the west.

●The Central Lowland

The plains east of the Missouri River are called the Central Lowlands. It stretches from the five Great Lakes to central Texas. Here is some of the most fertile land in the world. On these plains, the farmers grow corn, soybeans, and wheat. The Central Lowlands are also rich in oil and natural gas. Many of the large cities in the US are located in the Central Lowlands.

●The Great Plains

To the west of the Missouri River is the Great Plains. Most of the area is treeless grassland. Wheat and corn fields cover much of the plains. Great herds of cattle and sheep feed on its grasses. Places such as South Dakota's Ordway Prairie Preserve ensure that some of the natural prairie land survives.

Rocky Mountains

West of the Great Plains are the Rocky Mountains, spanning the country from Alaska to Mexico. High with rugged peaks and steep valleys, the Rocky Mountains rise over 4,260 me-ters above sea levels and form the continental divide of the United States. On one side of this great divide, all rivers flow west to the Pacific Ocean. On the other side, the rivers flow east. Rocky Mountains are younger than the Appalachians. Some of the people living in the Rocky Mountains earn their living by mining and logging. Rocky Mountains also attract visitors who come for sports and vacations. The Breathtaking sunsets, glaciated valleys（冰川谷）, pristine（原始的）forests, and snow-crested peaks—this is nature of drama.

Plateaus and the Great Basin

West of the Rockies are the two great plateaus: the Columbia Plateau in the north and the Colorado Plateau in the south, with the Great Basin in between. The Columbia Plateau is largely underlain by ancient lava（熔岩）flows, while Colorado Plateau includes spectacular canyons, high plateaus, and mountains.

A number of ancient salty lakes are found in the basin, including the famous Great Salt Lake of Utah. The rivers here do not flow toward the sea and most of them are shallow and salty. Many flow into the Great Salt Lake. This land receives little rainfall. Much of it is desert. Death Valley is on the western edge of this region. This valley, 200 kilometers long and 86 kilometers below the sea level, is the lowest point and hottest place in the US. There are few big cities in this part.The land near the Rocky Mountains is good for grazing cattle.

The Pacific Coastal Ranges

Farther west, along the coast, stands another great system of mountains, the Pacific Coastal ranges including the Sierra Nevada（内华达山脉）and Cascade ranges（喀斯喀特山脉）. It is truly a unique landscape consisting of various physiographic regions. With dynamic landforms such as California's white sand beaches in the south and the rugged and rocky coasts of Washington in the north, the Pacific Coast is very different from other coastal regions in the US. Another unique feature running along the Pacific Ocean is the Coast Ranges, which have peak elevations of about 1,200 meters in the state of Oregon.

The Canadian Shield

The last main region of North America is called the Canadian Shield, also known as the Laurentian Plateau（or Laurentian Highlands）, which covers an area of 4,790,000 km2and has the shape of a giant shield. It stands mainly in Canada, extending from Newfoundland in the east, to the Beaufort Sea in the northwest, and south through Wisconsin and Minnesota in the US.This is a large area of rocky hills covered with forests. It forms the central land mass of North America. Few people live in the northern region. But the land is rich in minerals such as nickel, copper, and silver. There are many streams and lakes in the Canadian Shield. These waters attract many Canadians and Americans from farther south for vacations.

Alaska and Hawaii

Alaska lies in the northwestern corner of North America, still mostly a rugged wilderness. Alaska covers 656,425 square miles, making it the largest of the 50 states and more than twice the size of Texas, the second largest state. Juneau（朱诺）is the capital of Alaska. Most of Alaska is surrounded by water. To the north is the Arctic Ocean; to the south is the Gulf of Alaska and Pacific Ocean; to the west is the Bering Sea. Alaska' s land borders Canada to the east and south. The geography can be categorized into four main areas including two mountain ranges, a central plateau, and the Arctic slope or coastal plain. It also includes the fertile farmland known as the Matanuska（马塔努斯卡河）Valley. Alaska contains 375 million acres of land and thousands of lakes. Permafrost（永久冻结带）is a major factor in the geography of Alaska. It covers most of the northern part of the State. Discontinuous or isolated patches also exist over the central portions in an overall area covering nearly a third of the State. The highest point in Alaska is Mt. McKinley at 20,320 feet above sea level（麦金利山）. In fact, Mt. McKinley is the highest point in North America. Yukon River（3,185 km long, of which 1, 149 km lie in Canada）is the longest river in Alaska and the fifth-longest river in North America.

About 3,680 kilometers across the Pacific Ocean is Hawaii, a long chain of tropical islands including 8 main islands and over a hundred atolls（环状珊瑚岛）and islets. The Hawaiian Islands were formed by volcanoes that pushed up from the seafloor millions of years ago. Hawaii is the largest of the habitable Hawaiian islands and covers 4,038 square miles. This island was formed by five volcanoes, two of which are still active and erupt intermittently（间歇地）.Waikiki Beach（威基基海滩）, located in Honolulu（火奴鲁鲁，即“檀香山”，美国夏威夷州首府和最大的城市）, is one of Hawaii's most popular attractions. Millions of tourists visit Hawaii to bask in the sun on its beautiful beaches.