Plains, plateaus, hills, mountains, canyons, and valleys are but a few of our planet’s amazing variety of landforms, the shapes Earth’s surface takes. As you read about these landforms, think about the ones you see in the area where you live. Types of Landforms Geographers recognize many different types of landforms, including plains, plateaus, hills, and mountains.
They categorize these landforms in terms of such characteristics as slope and local relief. Slope is the slant of the land. Relief means the difference between the highest and lowest points of a landform. Plains. Geographers classify a landform that is level or gently rolling as plains. This type of landform has little slope.
Most plains occur at low elevations-less than 1,000 feet above sea level. The Gulf Coastal Plain of the United States, for example, stretches from the Gulf of Mexico to southern Illinois, but no part of it is higher than 656 feet above sea level. A few plains, such as the western Great Plains of the United States, however, have higher elevations. Plateaus. A plateau is a generally flat landform that rises far above the surrounding land on at least one side.
The term tableland-another name for a plateau-provides a helpful image of the characteristics of this landform. Like a table, a plateau has a flat surface high off the ground. A feature characteristic of plateaus is their high elevation. The Colorado Plateau of the western United States, for example, ranges from 2,000 feet to more than 12,000 feet above sea level.
The Plateau of Tibet in China rises to more than 15,000 feet above sea level. Some plateaus, however, occur at lower elevations. Some plateaus are broken up by deep canyons. These canyons have high slope and high relief. For example, the Grand Canyon, which the Colorado River carved into the Colorado Plateau, has a local relief of from 5,000 feet to 9,000 feet.
Mountains and hills. Geographers classify as a mountain an elevated mass of land that projects above its surroundings. A hill is usually lower than a mountain and has a more rounded top. The slope of a hill can vary from very gentle to very steep.
Mountains rise dramatically from the surrounding land to an elevation thousands of feet above sea level. Mountains have steep slope. The summit is the highest point of a mountain. The highest mountain in the world is Mount Everest, in the Himalayas in Asia. Its summit is 29,028 feet above sea level.
Landforms and History Throughout history, landforms have had an important impact on human activity. For example, the fertile plains areas of North Africa and Southwest Asia nurtured the growth of the early civilizations you have read about in this chapter. High mountains have formed barriers that isolated some civilizations from outside influences for thousands of years.
One of the most important themes of history is the way in which people have adapted to the demands of their physical environment. Another important theme, however, has been people’s efforts to modify their environment for better living.