Sahara Wallpapers

Sahara Egypt - photo wallpapers: The Sahara [br](Arabic: الصحراء الكبرى, "The Great Desert") is the world's largest hot [br]desert, and second largest desert after Antarctica. At over 9,000,000 [br]km² (3,500,000 sq mi), it is almost as large as the United States, and [br]is larger than the 48 contiguous states. The Sahara defines the borders [br]of North Africa and has an intermittent history that may go back as [br]much as 2.5 million years. The name is an English rendition of [br]as-ṣaḥrā, the Arabic word for "desert" (صحراء (help·info)). The climate [br]of the Sahara has undergone enormous variation between wet and dry over [br]the last few hundred thousand years. During the last ice age, the [br]Sahara was bigger than it is today, extending south beyond its current [br]boundaries. The end of the ice age brought wetter times to the Sahara, [br]from about 8000 BC to 6000 BC, perhaps due to low pressure areas over [br]the collapsing ice sheets to the north. Once the ice sheets were gone, [br]the northern part of the Sahara dried out. However, not long after the [br]end of the ice sheets, the monsoon which currently brings rain to the [br]Sahara came further north and counteracted the drying trend in the [br]southern Sahara. The monsoon in Africa (and elsewhere) is due to [br]heating during the summer. Air over land becomes warmer and rises, [br]pulling in cool wet air from the ocean. This causes rain. [br]Paradoxically, the Sahara was wetter when it received more solar [br]insolation in the summer. In turn, changes in solar insulation are [br]caused by changes in the Earth's orbital parameters. By around 2500 BC, [br]the monsoon retreated south to approximately where it is today, leading [br]to the desertification of the Sahara. The Sahara is currently as dry as [br]it was about 13,000 years ago. These conditions are responsible for [br]what has been called the Sahara Pump Theory. Temperatures: The Sahara [br]desert has one of the harshest climates in the world. It has many [br]strong winds that blow from the north-east. Sometimes on the border [br]zones of the north and south, the desert will receive about 25 cm (10 [br]in.) of rain a year. The rainfall is usually torrential when it occurs [br]after long dry periods, which can last for years. Daytime temperatures [br]can be 58 °C (136 °F), but freezing temperatures aren't uncommon at [br]night, reaching as low as −6 °C (22 °F).

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Sahara Wallpapers @ Mega Wallpapers (08 Edition)