Category Science

Can sand dunes move?

Sand dunes can move slowly, causing deserts to spread over more fertile land. Continuous winds blow the sand to form crescent-shaped dunes. Sand from the top of the dune is blown farther away, and it gradually collects to form a new dune.

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How can people live in extreme climates?

Over millions of years, the human body has altered to suit the climate of the regions we inhabit. In general the hotter the region, the darker the skin of its inhabitants. Also, many people from Asia have a fold of skin in their eyelid to protect them from strong sunlight. People living in hot climates do not need a fat layer to keep warm, so they are usually slim. The Inuits of the Arctic, however, are mostly shorter and stockier to help conserve heat. 

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Which are the wettest places on the Earth?

Tropical rainforests are among the wettest places in the world. In general, most rainfall occurs on the sides of hills and mountains. The wettest place of all is Cherrapunji, in Assam, India. It faces the full force of the monsoon winds that sweep in from the Indian Ocean in July. Their warm, damp air rises in the Himalayan foothills, causing torrential rain. Mount Wai-‘ale-‘ale in Hawaii has the wet days each year. It rains on 350 days on average, and the annual rainfall is the highest recorded anywhere.

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What is permafrost?

Permafrost is a layer of ice and frozen soil that never thaws. It lies beneath nearly one-quarter of the Earth’s surface, throughout Alaska, Canada and Russia. Sometimes the soil in these places is frozen to a depth of up to 1,500 m. The surface layers may melt enough in summer for plants to grow, but the soil beneath is permanently frozen.

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Are there places where nothing can live?

Hot volcanic lava is probably the only place on the Earth’s surface where there is no life at all. Living things have evolved to survive in the harshest environments. Tiny bacteria can be found everywhere on the Earth, even buried in thick ice at the poles or in the very deepest parts of the ocean. 

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Where are the most extreme temperatures found?

Libya and the Antarctic have recorded the most extreme temperatures. The hottest shade temperature was in Libya in 1922, when the temperature in the Sahara desert reached 58 °C. Temperatures nearly as high as this were recorded in Death Valley in the USA in 1913. The coldest ever recorded temperature was in Antarctica in 1983, when Russian scientists measured a temperature low of – 89.2°C.

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The desert process

Deserts were once green and fertile areas, until a climate change altered them permanently. Just a small reduction in rainfall causes plants to die off. Without plant roots to bind and nourish the soil, the land gradually becomes barren. Soon the animals move away, and only desert remains. Very few deserts are completely barren, and plants and animals have evolved to live in the driest conditions, conserving their body water so they do not need to rely on rainfall.

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Are there cold deserts?

Antarctica is the biggest cold desert in the world. All of its water is locked up in ice and snow, so nothing can grow. The Gobi desert in Mongolia and western China is also very cold in the winter, when temperatures drop below freezing. However, it is hot in the summer.

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What is a mirage?

Mirages form in hot deserts, where the air is so hot it bends and distorts light rays. The shimmering images that a mirage produces have often tricked travellers in deserts. People think that they can see a town or oasis on the horizon, but in reality there is none. 

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Where is the world’s driest place?

The world’s driest place is the Atacama Desert in Chile. It is a narrow strip between the Andes and the Pacific, where the first rain for 400 years fell in 1971. Like other hot deserts, the Atacama lies in a region where air pressure is constantly high, with little air movement or cloud. Rainfall is very low in other deserts. Near Cairo, Egypt, annual rainfall averages about 28 mm each year, while in Bahrain, on the edge of the Arabian Desert, there is as much as 81 mm of rainfall. The rain may come in a single heavy storm, and some years there is no rainfall at all. 

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How much of the world is covered by desert?

About one-third of the world’s land surface is covered by desert. Desserts are found wherever there is too little water to allow much plant life to grow. This lack of vegetation leaves large areas of soil exposed. The largest desert in the world is the Sahara in Africa. It has an area of about 9 million sq km. 

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