How was the Sahara Desert formed·
It is generally believed that the Sahara Desert was formed no earlier than the Quaternary Period. A large number of geological records show that there was a significant drought in the Sahara at the beginning of the Quaternary Ice Age. The degree of drought in the Sahara is mainly affected by the African summer monsoon.
Before the Quaternary, the changes in the African summer monsoon showed an obvious precessional cycle (about 20,000 years); after the beginning of the Quaternary glacial period, the interglacial cycle (about 40,000 years or 100,000-year cycle) begins to affect the intensity of the African summer monsoon.
Researchers from the Institute of Atmospheric Sciences, Chinese Academy of Sciences, in collaboration with foreign scientists, discovered that the late Miocene Toltonian (approximately 7 million to 11 million years ago) was a critical period when drought in North Africa intensified the formation of the Sahara Desert. Scientists used the Norwegian Earth System Model and the Public Atmospheric Model to reveal that the contraction of the Tethys Sea during the Toltonian stage caused the African summer monsoon to significantly weaken, and an arid desert environment was formed across a large area of North Africa.
The contraction of the Tethys Sea not only led to changes in the average climate state of North Africa, but also strengthened the response of the African summer monsoon to orbital changes, and subsequently became the main factor controlling changes in the extent of the Sahara Desert. ?
(1) North Africa is located on both sides of the Tropic of Cancer and is controlled by the subtropical high pressure belt all year round. Dry and hot downdrafts prevail. The African continent is narrow in the south and wide in the north, and is controlled by the subtropical high pressure belt over a large area. , a wide area of dry heat.
(2) North Africa is closely adjacent to the Asian continent, and the northeast trade wind blows from the eastern land, making it difficult for precipitation to occur, making North Africa drier.
(3) The coastline of North Africa is straight, and there is the Ethiopian Plateau to the east, which blocks moist airflow and prevents the vast inland areas from being affected by the ocean.
(4) The Canary Cold Current passes through the west coast of North Africa, which has a cooling and dehumidifying effect on the western coastal areas, causing the desert to approach the west coast.
(5) North Africa has a single terrain, flat terrain, moderate fluctuations, and a single climate, forming a large area of desert area.
Extended information:
The climate of the Sahara Desert is hot and dry. However, what is puzzling is that in this extremely dry and water-deficient mining land with cracked soil and sparse plants, there was once a prosperous ancient civilization. The many beautiful and colorful large-scale murals on the desert are the crystallization of this ancient civilization.
Although the Sahara Desert (excluding the Nile Valley) is as large as the United States, its inhabitants are estimated to be only 2.5 million, or less than 0.4 people per square kilometer. A huge area is deserted, but as long as the thin vegetation can support livestock or there is a reliable water source, the scattered people will survive in the most difficult environment and precarious ecological environment in the world.
Archaeology has proven that various people have settled in the Sahara Desert one after another, and the cultivation and domestication of animals and plants have led to professional specialization. Foreign trade also developed, and copper from Mauritius found its way into the Bronze Age civilization of the Mediterranean in 2000 BC.
The great migration of nomads facilitated their involvement in trade throughout the Sahara Desert. Oasis residents in the Sahara are vulnerable to attacks by the Sanhayans (Berbers) and other camel-riding nomads, many of whom entered the desert to escape the chaos and wars of the late Roman period in North Africa. Many of the remaining oasis inhabitants, among them the Haratin, were conquered by nomads.
The expansion of Islam to North Africa from the 7th to the 11th century inspired more Berbers and Arab groups who wanted to maintain their traditional beliefs to move into the Sahara Desert. Islam eventually expanded through trade routes and became the dominant social force in the desert.
Baidu Encyclopedia-Sahara Desert