When people think of a desert, they imagine hot, dry and barren areas without water. Although this is one type of desert, there are other areas that most would not think of as a desert.
Most of us are familiar with the sand dunes of the Sahara desert but there are deserts in Antarctica as well. A desert doesn’t have to be barren. In fact, deserts can support diverse populations of plant life and even animals that are adapted to live in those climatic conditions. It is commonly believed that a desert is a region that receives very little precipitation but more accurately, a desert is an area where more water is lost through evaporation than is gained from precipitation. Altitude and winds, among other factors work to create differences among the world’s deserts.
There are four major types of deserts, hot and dry, semi-arid, coastal, and cold. Hot and dry deserts are very warm or hot throughout the year with very little rainfall. Plants usually consist of woody trees and ground shrubs. Native animals are generally nocturnal coming out at night when the temperatures are cooler. Semi-arid deserts are generally warm with low amounts of rainfall. Native plants such as cacti are found in these areas as well as lizards and small mammals. Coastal deserts host a moderately cool to warm environment suitable for fleshy plants, amphibians and various mammals. Cold deserts are found in areas such as Antarctica and Greenland. Plants such as those with spiny leaves and mammals suitable for the environment exist in such desert areas.
Deserts have existed for millions of years although their location and forms have changes throughout the history of our planet. Most deserts are located within two belts near the equator. High atmospheric pressure in the region brings cold, dry air from higher altitudes closer to land. The sun heats the air causing low humidity and high ground temperatures. Deserts can also be formed by the rain shadow effect. This occurs where there are two mountain ranges, one to the east and one to the west which prevent ocean air from reaching land. The region between the mountains becomes very dry. Cold deserts such as those in Antarctica are products of the extreme cold climate. Surface water remains frozen and the air is too cold to contain more than minute amounts of moisture.
Although most deserts are viewed as being totally devoid of water, it can exist below the surface if not on the surface. Sub-surface water often collects deep within the earth over centuries. Although deserts are known for their dry, arid climatic conditions, deserts may have rainy seasons. In extremely hot areas the rain may evaporate before reaching the ground.
Temperatures can be extreme in desert regions. It can be over 100 degrees during the day and drop below freezing at night.
The Sahara is the largest desert in the world. It covers an area of 3,500,000 square miles and has a population of 2 million people.
The Gobi desert is considered to have the harshest climatic with extreme temperatures as low as twenty to forty below zero in the winter and well over 100 degrees Fahrenheit in the summer.
There are an estimated 1,200 plant species found in the Sahara desert.
It is estimated that at least thirty species of mammals inhabit the Gobi desert.