write a short note on climate in desert and how it is formed
Answers
Deserts are areas that receive very little precipitation. People often use the adjectives “hot,” “dry,” and “empty” to describe deserts, but these words do not tell the whole story. Although some deserts are very hot, with daytime temperatures as high as 54°C (130°F), other deserts have cold winters or are cold year-round. And most deserts, far from being empty and lifeless, are home to a variety of plants, animals, and other organisms. People have adapted to life in the desert for thousands of years.
One thing all deserts have in common is that they are arid, or dry. Most experts agree that a desert is an area of land that receives no more than 25 centimeters (10 inches) of precipitation a year. The amount of evaporation in a desert often greatly exceeds the annual rainfall. In all deserts, there is little water available for plants and other organisms.
Deserts are found on every continent and cover about one-fifth of Earth’s land area. They are home to around 1 billion people—one-sixth of the Earth’s population.
Although the word “desert” may bring to mind a sea of shifting sand, dunes cover only about 10 percent of the world’s deserts. Some deserts are mountainous. Others are dry expanses of rock,sand or salt flats.
Desert Characteristics
Humidity—water vapor in the air—is near zero in most deserts. Light rains often evaporate in the dry air, never reaching the ground. Rainstorms sometimes come as violent cloudbursts. A cloudburst may bring as much as 25 centimeters (10 inches) of rain in a single hour—the only rain the desert gets all year.
Desert humidity is usually so low that not enough water vapor exists to form clouds. The sun’s rays beat down through cloudless skies and bake the land. The ground heats the air so much that air rises in waves you can actually see. These shimmering waves confuse the eye, causing travelers to see distorted images called mirages.
Temperature extremes are a characteristic of most deserts. In some deserts, temperatures rise so high that people are at risk of dehydration and even death. At night, these areas cool quickly because they lack the insulation provided by humidity and clouds. Temperatures can drop to 4°C (40°F) or lower.
Winds at speeds of about 100 kilometers per hour (60 miles per hour) sweep through some deserts. With little vegetation to block it, the wind can carry sand and dust across entire continents and even oceans. Windstorms in the Sahara hurl so much material into the air that African dust sometimes crosses the Atlantic Ocean.
First-time visitors to deserts are often amazed by the unusual landscapes, which may include dunes, towering bare peaks, flat-topped rock formations, and smoothly polished canyons. These features differ from those of wetter regions, which are often gently rounded by regular rainfall and softened by lush vegetation.
Water helps carve desert lands. During a sudden storm, water scours the dry, hard-baked land, gathering sand, rocks, and other loose material as it flows. As the muddy water roars downhill, it cuts deep channels, called arroyos or wadis. A thunderstorm can send a fast-moving torrent of water—a flash flood—down a dry arroyo. A flash flood like this can sweep away anything and anyone in its path. Many desert regions discourage visitors from hiking or camping in arroyos for this reason.
Even in a desert, water and wind eventually wear away softer rock. Sometimes, rock is carved into tablelike formations such as mesas and buttes. At the foot of these formations, water drops its burden of gravel, sand, and other sediment, forming deposits called alluvial fans.
Many deserts have no drainage to a river, lake, or ocean. Rainwater, including water from flash floods, collects in large depressions called basins. The shallow lakes that form in basins eventually evaporate, leaving playas, or salt-surfaced lake beds. Playas, also called sinks, pans, or salt flats, can be hundreds of kilometers wide.