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**1. Geography and Climate of the Sahara Desert:**
– Sahara spans North Africa, covering 9.2 million square kilometers.
– Largest hot desert globally excluding fertile regions like the Mediterranean coast.
– Sahara’s climate is hot and arid, with virtually no rainfall and dominated by a continental tropical air mass.
– Located in the horse latitudes, the Sahara experiences extreme temperatures exceeding 38 to 40°C during summer.
– Receives over 3,600 to 4,000 hours of bright sunshine annually, making it ideal for solar energy production.

**2. Flora, Fauna, and Landforms of the Sahara:**
– Sparse vegetation in hyperarid central Sahara with some trees and shrubs in wadis.
– Landforms include rocky hamada, sand dunes reaching over 180 meters high, and unique formations like the Richat Structure.
– Sahara’s limits defined by botanical and climatic criteria.
– Ecoregions like the Atlantic coastal desert, Sahara desert ecoregion, and South Saharan steppe and woodlands exhibit variations in temperature, rainfall, and vegetation.
– Saharan Halophytics ecoregion features salt-adapted plant communities in saline depressions.

**3. Human Presence and Desertification in the Sahara:**
– Important cities like Nouakchott, Timbuktu, and Agadez support life in the desert.
– Oases play a crucial role in sustaining human presence in arid regions.
– Sahara Pump Theory describes the cycle of Sahara transitioning between savanna grassland and desert conditions.
– Evidence for cycles in Sahara’s climate includes prehistoric rainfall tracking and changes in the movement of the ITCZ.
– The Great Green Wall project aims to combat desertification in the Sahel region.

**4. Prehistoric Climate and Orbital Monsoon Hypothesis:**
– Sahara’s formation linked to weakened monsoons due to glaciation and the drying up of the ancient Tethys Sea.
– Climate in the Sahara has fluctuated between wet and dry periods over hundreds of thousands of years.
– Orbital Monsoon Hypothesis suggests long-term monsoon variations due to changes in Earth’s orbit.
– Changes in insolation influence global monsoonal patterns.
– Sahara was larger during the last glacial period, and Lake Chad is a remnant of a former inland sea.

**5. Unique Ecoregions and Biodiversity in the Sahara:**
– Sahara has distinct ecoregions like West Saharan Montane Xeric Woodlands and Tibesti-Jebel Uweinat Montane Xeric Woodlands.
– West Saharan Montane Xeric Woodlands cover volcanic highlands supporting diverse plant species.
– Tibesti-Jebel Uweinat Montane Xeric Woodlands have higher rainfall and cooler temperatures, home to rare endemic plant species.
– Tanezrouft, one of the most arid regions in the Sahara, lacks vegetation due to harsh environmental conditions.
– Sahara supports around 2800 species of vascular plants, with a quarter being endemic and unique adaptations to saline environments in certain areas.

Sahara (Wikipedia)

The Sahara (/səˈhɑːrə/, /səˈhærə/) is a desert spanning across North Africa. With an area of 9,200,000 square kilometres (3,600,000 sq mi), it is the largest hot desert in the world and the third-largest desert overall, smaller only than the deserts of Antarctica and the northern Arctic.

The Sahara taken by Apollo 17 astronauts, 1972
Geographical map of the Sahara
Length4,800 km (3,000 mi)
Width1,800 km (1,100 mi)
Area9,200,000 km2 (3,600,000 sq mi)
Native name
  • Arabic: الصحراء الكبرى
  • aṣ-ṣaḥrā' al-kubrá
  • "The greatest desert"
Coordinates23°N 13°E / 23°N 13°E / 23; 13

The name "Sahara" is derived from Arabic: صَحَارَى, romanizedṣaḥārā /sˤaħaːraː/, a broken plural form of ṣaḥrā' (صَحْرَاء /sˤaħraːʔ/), meaning "desert".

The desert covers much of North Africa, excluding the fertile region on the Mediterranean Sea coast, the Atlas Mountains of the Maghreb, and the Nile Valley in Egypt and the Sudan.

It stretches from the Red Sea in the east and the Mediterranean in the north to the Atlantic Ocean in the west, where the landscape gradually changes from desert to coastal plains. To the south it is bounded by the Sahel, a belt of semi-arid tropical savanna around the Niger River valley and the Sudan region of sub-Saharan Africa. The Sahara can be divided into several regions, including the western Sahara, the central Ahaggar Mountains, the Tibesti Mountains, the Aïr Mountains, the Ténéré desert, and the Libyan Desert.

For several hundred thousand years, the Sahara has alternated between desert and savanna grassland in a 20,000-year cycle caused by the precession of Earth's axis (about 26,000 years) as it rotates around the Sun, which changes the location of the North African monsoon.

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