Plateau

A plateau is a large, flat area of land that stands high above the land around it. The word comes from a French word that means "flat." Plateaus can be small or huge. Some cover only a few square miles. Others stretch across whole regions of a continent. They are one of the four main kinds of landforms, along with mountains, plains, and hills.

Plateaus form in a few different ways. Some are pushed up from below when slow movements deep inside the Earth lift big chunks of land. The Colorado Plateau in the western United States formed this way. It rose up over millions of years and now sits more than a mile above sea level. Other plateaus form when lava flows out of long cracks in the ground. The lava spreads out, cools, and hardens into thick sheets of rock. The Columbia Plateau in Washington and Oregon was built from layer after layer of ancient lava.

A few plateaus are leftovers. They were once part of taller mountains that wore down over millions of years. Wind, rain, and rivers slowly carried the softer rock away. The harder rock stayed behind as a high, flat surface.

The biggest plateau on Earth is the Tibetan Plateau in Asia. It covers about one million square miles, almost a third the size of the United States. Its average height is about 14,800 feet, nearly three miles up. The air there is so thin that visitors often get sick until their bodies adjust. The plateau is so massive that it pushes warm air upward and helps create the monsoon rains that fall across India each summer.

Plateaus often have steep edges called escarpments. Rivers running across the flat top can cut deep into the rock over time. This is how many famous canyons formed. The Grand Canyon was carved into the Colorado Plateau by the Colorado River. The flat land you see at the rim is the top of the plateau itself.

People have lived on plateaus for thousands of years. Many plateaus have rich soil for farming and good grass for animals. Cities like Mexico City and Denver sit on plateaus. The next time you see a flat-topped landform that towers over the country around it, you are probably looking at one.