Deserts are generally arid and dry areas, that is, they receive very little precipitation throughout the year (less than 250 mm of water per year) and usually have average temperatures of 54°C during the day and less than 0°C at night. night, however, they are planet earth environments that also house animal life, a variety of plants and organisms, in addition, there are people and populations that have adapted their lives around deserts, so their study is necessary.
What is a desert?
The formal definition of a desert It is that it is a region or zone of the earth that is very arid or dry and only has a maximum of 15% vegetation on its surface, a low amount of surface water and where rainfall does not exceed 25 cm per year on average.
Generally, deserts tend to be associated with places with high temperatures, but the definition of a desert depends on its aridity. In fact, there are hot and cold deserts.
The low percentage of vegetation, water and rain are called desert conditions.
Due to the lack of water, deserts do not contain permanent streams, except those that bring water from temperate regions to other places.
Types of deserts
It should be noted that the definition of a desert it depends on the aridity of a region, not its temperature.
Every desert on Earth has unique landscape and vegetation characteristics that set it apart from the rest. Geologists group deserts into at least seven different classes, based on the environment in which the desert forms.
Cold deserts
The cold deserts, are those where temperatures generally remain below about 20 ° C during the year.
The cold deserts they exist at high latitudes where the Sun’s rays strike the Earth obliquely and therefore do not provide much energy, at high elevations where the air is too thin to hold much heat, or on land adjacent to cold oceans, where cold water absorbs heat from the air above.
Hot deserts
Hot deserts are those where daytime summer temperatures exceed 35 °C.
The hot deserts They thrive at low latitudes where the sun’s rays strike the desert at a high angle, at low elevations where dense air can hold a lot of heat, and in regions distant from the cooling effect of cold ocean currents.
The highest temperatures recorded on Earth occur in low-latitude, low-elevation deserts: 58 °C (136 °F) in Libya and 57 °C (133 °F) in Death Valley, California.
Subtropical deserts
Subtropical deserts (such as the Sahara, Arabian, Kalahari, and Australia) are formed due to the regional pattern of air circulation in the atmosphere.
At the equator, the air becomes warm and humid, since the sunlight is intense and the water evaporates quickly from the ocean. Warm, moisture-laden air rises high above the equator. As this air rises, it expands and cools, and can no longer hold as much moisture.
The water condenses and falls in downpours that feed the exuberance of the equatorial jungle. The now dry air high in the troposphere spreads laterally to the north or south.
When this air reaches latitudes of 20°C to 30°C, a region called the subtropics, it becomes cold and dense enough to sink.
Because the air is dry, clouds do not form, and intense solar radiation hits the Earth’s surface.
The sinking dry air becomes denser and warms, absorbing any moisture present.
In regions swept by this hot air on its return journey to the equator, evaporation rates greatly exceed rainfall rates, drying out the land.
Coastal deserts formed along cold ocean currents
Cold ocean water cools the overlying air by absorbing heat, thus decreasing the air’s ability to hold moisture. For example, the cold Humboldt Current, which carries water north from Antarctica to the west coast of South America, cools air blowing east over the coast.
The air is so dry when it reaches the coast that it rarely rains in the coastal areas of Chile and Peru.
As a result, this region is home to a desert landscape, including one of the driest deserts in the world, the Atacama. Some parts of this narrow desert received no rain at all between 1570 and 1971.
Deserts formed in rain shadows
As air flows over the sea toward a coastal range, the air must rise. As the air rises, it expands and cools. The water it contains condenses and falls as rain down the flanks of the mountains to the sea, feeding a coastal rainforest. When the air finally reaches the inner side of the mountains, it has lost all its moisture and can no longer provide rain.
As a consequence, a rain shadow forms, and the land below the rain shadow becomes a desert. A rain shadow desert can be found east of the Cascade Mountains in Washington state.
Continental deserts
As air masses move across a continent, they lose moisture as it rains, even in the absence of a coastal range.
Therefore, when an air mass reaches the interior of a wide continent, it becomes so dry that the land below becomes arid.
The largest present-day example of such a continental inland desert, the Gobi, is found in central Asia.
Deserts of polar regions
So little precipitation falls in Earth’s polar regions (north of the Arctic Circle and south of the Antarctic Circle) that these areas are, in fact, arid. The polar regions are dry partly for the same reason that the subtropics are dry (the global pattern of air circulation means that the air flowing over these regions is dry), and partly for the same reason that the polar areas are dry. shorelines along cold currents are dry (cold air retains little moisture).
General characteristics of deserts
The weather
The climate in the deserts is related to an arid environment and very extreme variable temperatures, that is, they are usually very hot during the day and very cold at night and early morning.
In addition, they are usually very dry environments.
Room temperature
As mentioned during the day, they are usually very hot environments and can easily exceed 40 °C, especially in summer.
Occasionally at night and early morning, the temperature usually drops even below 0 °C.
On average in winter the temperature is between 20 °C to 30 °C
The soil in the desert
Due to the high erosion of the wind, the extreme climate, the arid and dry environment, the soil has very little opportunity to develop in a desert, therefore, in these places the soils are very thin, of sandy composition, with a high percentage of rocky clasts and gray colors.
Desert soils are very dry and because they are sandy when it rains, they immediately absorb rainwater and do not maintain soil moisture, thus preventing vegetation from developing.
Regarding the chemical composition, it is common for desert soils to be rich in saline minerals or halides such as halite or gypsum or what are commonly called evaporites.
Vegetation and plants in a desert
Plants that have managed to adapt to the environmental conditions of a desert are known as xerophytic plants or vegetation.
This class of plants and vegetation is characterized by the fact that they have small leaves, long and deep roots, usually have thorns, and their structure (stems, skin) are usually very thick and waxy.
Here it should be noted that its roots are deep because the water in deserts is also usually very deep, and the plants need to reach that water in some way, so the roots easily exceed 7 meters in length.
Its structure and skin on the stems of the plant are usually thick in order to prevent the evaporation of the water that is stored in the plant.
Generally, the thorns tend to replace the leaves and it is also due to the fact that some thorns avoid wasting water and also provide protection against animals.
The most common examples of plants and vegetation in a desert are cacti.
The water in the desert
As we already know, the soil in deserts is highly sandy and dry, so when the rain falls all the water is absorbed into the depths of the soil, it is common for the water in the desert to accumulate at a depth greater than 7 meters..
In fact, the largest amount of water that exists in these desert environments is groundwater and the populations that live near those places hire geologists who are dedicated to searching for groundwater in order to extract it properly.