Sahara Desert

Sahara Desert

Sahara desert is the largest desert in the world. It is approximately cover 3.5 million square miles (approx 9,064,958 sq. km). The hottest temperature recorded in Sahara desert is 60 degree Celsius or 140 degree fahrenheit.

Before the great desert was born, North Africa had a moister, semiarid climate. A few lines of evidence, including ancient dune deposits found in Chad, had hinted that the arid Sahara may have existed at least 7 million years ago.

The great desert was born some 7 million years ago, as remnants of a vast sea called Tethys closed up. The movement of tectonic plates that created the Mediterranean Sea and the Alps also sparked the drying of the Sahara some 7 million years ago, according to the latest computer simulations of Earth’s ancient climate.

Though North Africa is currently covered by the world’s largest non-polar desert, climate conditions in the region have not been constant there for the last several million years. Subtle changes in Earth’s tilt toward the sun periodically increase the amount of solar energy received by the Northern Hemisphere in summer, altering atmospheric currents and driving monsoon rains. North Africa also sees more precipitation when less of the planet’s water is locked up in ice. Such increases in moisture limit how far the Sahara can spread and can even spark times of a green Sahara, when the sparse desert is replaced by abundant lakes, plants and animals.

Sahara Desert Coordinates 23.4162 N, 25.6628 E

Before the great desert was born, North Africa had a moister, semiarid climate. A few lines of evidence, including ancient dune deposits found in Chad, had hinted that the arid Sahara may have existed at least 7 million years ago. But without a mechanism to explain how it emerged, few scientists thought that the desert we see today could really be that old. Instead, most scientists argue that the Sahara took shape just 2 to 3 million years ago. Terrestrial and marine evidence suggest that North Africa underwent a period of drying at that time, when the Northern Hemisphere started its most recent cycle of glaciation.

About 250 million years ago, a huge body of water called the Tethys Sea separated the supercontinents of Laurasia to the north and Gondwana to the south. As those supercontinents broke apart and shuffled around, the African plate collided with the Eurasian plate, birthing the Alps and the Himalayas but closing off the bulk of the Tethys Sea. As the plates kept moving, the sea continued to shrink, eventually diminishing into the Mediterranean.

Their simulations take into account changes in Earth’s orbital position, atmospheric chemistry and the ratio of land to ocean as driven by tectonic forces. The models shows that precipitation in North Africa declined by more than half about 7 million years ago, causing the region to dry out. But this effect could not be explained by changes in vegetation, Earth’s tilt or greenhouse gas concentrations leaving tectonic action.

The effects of local surface low pressure are extremely limited because upper-level subsidence still continues to block any form of air ascent. Also, to be protected against rain-bearing weather systems by the atmospheric circulation itself, the desert is made even drier by its geographical configuration and location. Indeed, the extreme aridity of the Sahara is not only explained by the subtropical high pressure: the Atlas Mountains of Algeria, Morocco and Tunisia also help to enhance the aridity of the northern part of the desert. These major mountain ranges act as a barrier, causing a strong rain shadow effect on the leeward side by dropping much of the humidity brought by atmospheric disturbances along the polar front which affects the surrounding Mediterranean climates.

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