Problem: 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 his geographical configuration and location. Indeed, the extreme aridity of the Sahara can't be only explained by the subtropical high pressure. The Atlas Mountains, found in 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.
What is the sole cause of extreme aridity in the Sahara?
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Answer: unanswerable

Problem: But early in the 16th century, a brilliant new red appeared in Europe. When the Spanish conquistador Hernan Cortes and his soldiers conquered the Aztec Empire in 1519-1521, they discovered slowly that the Aztecs had another treasure beside silver and gold; they had the tiny cochineal, a parasitic scale insect which lived on cactus plants, which, when dried and crushed, made a magnificent red. The cochineal in Mexico was closely related to the Kermes varieties of Europe, but unlike European Kermes, it could be harvested several times a year, and it was ten times stronger than the Kermes of Poland. It worked particularly well on silk, satin and other luxury textiles. In 1523 Cortes sent the first shipment to Spain. Soon cochineal began to arrive in European ports aboard convoys of Spanish galleons.
What happened in 1519?
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Answer: unanswerable

Problem: Namibia (i/nmbi/, /n-/), officially the Republic of Namibia (German: Republik Namibia (helpinfo); Afrikaans: Republiek van Namibie) is a country in southern Africa whose western border is the Atlantic Ocean. It shares land borders with Zambia and Angola to the north, Botswana to the east and South Africa to the south and east. Although it does not border Zimbabwe, a part of less than 200 metres of the Zambezi River (essentially a small bulge in Botswana to achieve a Botswana/Zambia micro-border) separates it from that country. Namibia gained independence from South Africa on 21 March 1990, following the Namibian War of Independence. Its capital and largest city is Windhoek, and it is a member state of the United Nations (UN), the Southern African Development Community (SADC), the African Union (AU), and the Commonwealth of Nations.
How far away is Namibia to the Zambezi River?
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Answer:
200 metres