Deserts questions

The Saharan Air Layer (SAL) is an extremely hot, dry and sometimes dust-laden layer of the atmosphere that often overlies the cooler, more-humid surface air of the Atlantic Ocean. The SAL passes over the Canary Islands where the phenomenon is named "Calima" and manifests as a fog that reduces visibility and deposits a layer of dust over everything.

The Negev is a desert and semidesert region of southern Israel. The region's largest city and administrative capital is Beersheba (pop. 207,551), in the north. At its southern end is the Gulf of Aqaba and the resort city of Eilat. The desert is home to the Ben-Gurion University of the Negev, whose faculties include the Jacob Blaustein Institutes for Desert Research.

The crescentic dune, also called the barchand dune, is the most common type of sand dune. As its name suggests, this dune is shaped like a crescent moon with points at each end, and it is usually wider than it is long. Crescentic dunes form when winds blow from one direction. This dune traverses desert surfaces faster than any other type of dune. The migrating dunes in China are crescentic dunes.

Simoom is a strong, dry, desert wind. The name means "poison wind" and is given because the sudden onset of simoom may also cause heat stroke. Its temperature may exceed 54 °C (129 °F) and the humidity may fall below 10%.

One of the most interesting mysteries of Death Valley National Park is the sliding rocks at Racetrack Playa (a playa is a dry lake bed). These rocks can be found on the floor of the playa with long trails behind them. Somehow these rocks slide across the playa, cutting a furrow in the sediment as they move. n 2013, scientists were able to directly observe the "stone journey" and discover in what conditions this phenomenon occurs.

The Sahara is the largest hot desert and the third largest desert in the world after Antarctica and the Arctic. Its area of 9,200,000 square kilometres (3,600,000 sq mi) is comparable to the area of China or the United States. The name 'Sahara' is derived from dialectal Arabic word for "desert".

The Fata Morgana occurs because rays of light are bent when they pass through air layers of different temperatures in a steep thermal inversion, where an atmospheric duct has formed. It significantly distorts the object on which it is based, often such that the object is completely unrecognizable. The Fata Morgana may be seen on land or at sea, in polar regions, or in deserts. It may involve almost any kind of distant objects, including boats, islands, and the coastline.

The area Błędów Desert lies mainly on the Silesian Highlands in Poland. The Błędowska Sands is Central Europe's largest accumulation of loose sand in an area away from any sea, deposited thousands of years ago by a melting glacier. It occupies an area of 32 km2 (12 sq mi). The sands have an average depth of 40m, up to 70m at the maximum.

The Ténéré Tree was a solitary acacia, the only one for over 400 km, located in northeast Niger. It was a landmark on caravan routes through the Sahara Desert, so well known that it and the Lost Tree to the north are the only trees to be shown on a map at a scale of 1:4,000,000. It was knocked down in 1973 by a drunk truck driver.

The initial research works and discoveries of dinosaur fossil sites and their tracks in Mongolia started in the 1920s. Throughout this time, there have been many national and international field expeditions conducted in the country, and more than 80 genera of dinosaurs have been found in the Mongolian Gobi Desert.