More than a third of the Earth’s land is covered by desert, but very little of it has the sandy appearance that we usually think of when deserts are mentioned. Most of the world’s deserts are barren, stony places.
Most of the world’s surface is covered in water, in the form of oceans. The remaining landmass of Earth amounts to approximately 29 percent of the surface. Of this remaining 29 percent, deserts of all types constitute an estimated 33 percent, or one-third, of the Earth’s total landmass. This large percentage is due in part to the vastness of the world’s largest desert — Antarctica.
Though sand dunes and cacti might immediately spring to mind when people think about deserts, the term “desert” is actually more inclusive and refers to a variety of different land types, from arid canyons to frigid polar plains. Deserts, which make up a large amount of the Earth’s land mass, are home to a diverse collection of plants, animals and landforms.
Deserts are primarily defined by their dryness. A desert can be any land area that has an annual deficit of water — that is, an area where more moisture evaporates than is taken in through any form of precipitation. In more concrete terms, a desert is commonly defined as any area that receives less than 254 millimeters (10 inches) of precipitation (in the form of snow or rain) in a given year.
Because the definition of a desert is so broad and focused on aridness, there are many different and varied types of deserts. In general, deserts may be hot, like the Sahara, or cold, like Antarctica. Beyond that, deserts may be broken into several more categories, depending on their geographic and physical features and how they form. For example, rain shadow deserts are formed when landforms like mountains interrupt cloud cover and prevent precipitation on the protected, or leeward, side of a mountain range.
Antarctica averages less than 5 centimeters (2 inches) of precipitation in the form of snow each year. The icy nature of Antarctica is due to the accumulation of snow, which, despite its small amount, still falls faster in most regions than it can evaporate due to frigid temperatures. This massive polar desert accounts for approximately 14.2 million square kilometers (5.5 million square miles) of the Earth’s surface. The largest hot desert on Earth is Africa’s Sahara desert, which makes up 8.6 million square kilometers (3.3 million square miles) of the planet’s surface. This arid land receives an average of less than 25 millimeters (1 inch) of rain each year.
Picture Credit : Google