Different types of deserts

About a fifth of the world’s land is made up of deserts. While some re rocky, others are stony or sandy. Deserts are landscapes that are absolutely barren and where there is rare or no growth of vegetation. The world’s deserts follow a pattern i.e. most of the deserts are confined within 15 degrees to 30 degrees parallel to latitude north and south of equator.

They lie in the trade wind belt on the western part of the continents where trade winds blow offshore. They are bathed by cold winds which produce a desiccating effect. So the moisture is not easily condensed into precipitation.Dryness and aridity is the key note; such deserts are tropical hot deserts or trade wind deserts, that include the great Sahara Desert, Arabian Desert, Iranian Desert, the Great Australian Desert and the deserts of south west U.S.A, and northern Mexico.

In the continental interiors of the mid-latitudes, deserts such as the Gobi and Turkestan are characterised by extremes of temperatures. The work of winds and water in eroding elevated uplands, transporting the worn off materials and depositing them elsewhere lead to the formation of deserts. There are fourteen kinds of deserts.

Wadi

An Arabic term that refers to a valley. In some cases, it can also refer to a dry riverbed that only experiences water when there is a heavy rain fall. Unlike other valleys, a Wadi has been cut and eroded by water. However, because it is situated in a desert, it rarely gets any water except during the rainy season. Deposition is very common in a feature such as this because of the fact that the water dries up and is no longer able to carry a load of sediment that it has.

Playas

An area of very dry land that is found below the sea level. Flats like this often consist of fine grained sediments such as salts. During the dry season, the surface of the lake is usually hard and rough, whereas in the rainy season it gets wet and soft. The water usually creates a small hole meaning there is a very shallow lake in the desert.

Alluvial Fans

Often found in the desert where periodic flash floods occur. They often have a large funnel shaped basin at the top which then creates a very narrow stream opening into an alluvial fan at the end of its course. These alluvial fans are often home to much more life and plant than the rest of the desert due to the fact that any nutritional sediment and water will end up here.

Bajada

When many alluvial fans all come together in one place or deposit in the same area, it creates a Bajada. Because of the gathering of all the fans, it means that there is much more water and sediment than usual and it is quite evenly spread throughout the whole Bajada.

Mesa

An elevated area of land that has very steep sides and a flat top. They are formed by the weathering and erosion of horizontally layered rocks that are lifted by the tectonic activity of the area. Due to the fact that some rocks erode faster than others, or others are stronger, it means that stronger rocks usually make it to the top and the weaker rock is at the bottom.

Butte

An isolated hill with very steep sides, and a small somewhat flat top. Typically they say that a mesa has a top wider than its height and a butte has a height larger than its width.

Canyon

A deep ravine between cliffs, often carved into the landscape by a river. They are formed when there is stronger rock on either side of where the water is eroding. This means that the water is able to cut vertically but not horizontally.

Deflation Hollow or Basin

Created by wind action. Fine grained particles from rocks that are easily weathered are carried away creating a hollow. As the hollow deepens they collect water during the rainy season. This water helps speed up the weathering of the rock creating more particles to be blown away by the wind. Due to this the hollow is able to deepen faster than the rest of the land surrounding it, creating a large hole in the ground.

Barchan

A sand ridge in the shape of an arc. Wind can often push the dunes through the desert, and they can stretch in size anywhere from a few meters to hundreds of meters long. They occur in the opposite direction of the parabolic dunes and have their steep slip face on the concave instead of the convex of the dune.

Parabolic Dunes

U or V-shaped mounds of sand that have elongated arms extending upwards. They are always associated with vegetation which helps anchor the trailing arms of the dune. They are found in areas where the wind only blows in one direction. Slip faces occur on the outer side of the dune and on the slopes of the elongated arms.

Pedestal Rock

A large boulder on top of a very narrow base. This occurs when there is soft rock underneath that is easily eroded and harder rock on top that cannot be eroded away.

Arch

Formed where there is soft rock surrounded by hard rock. Deep cracks penetrate into the sandstone layer and erosion wears away exposing the rocks layers and enlarging the surface cracks. Softer rock gets broken away by wind and the little amount of rain forming arches where the soft rock being broken away creates a hole in the harder rock.

Salt Flats

Formed where there are dry lake beds. It is an area of very dry land that occurs below the sea level. It receives much of the sediment that is deposited.

Badland

Formed where deep beds of easily eroded rock are exposed to erosion. The infrequent heavy rains are able to cut out stream channels. This results in gullies, carved hillsides and tall spires of the most resistant rock to erosion.