Category Environment

The Aralkum Desert, in Uzbekistan and Kazakhstan. It was once a water body called the Aral Sea, but water from the two rivers that fed it was diverted for agriculture and, gradually, by 2000, most of the sea had become a desert.

The white salt terrain left behind by the desiccation of the southern Aral Sea is now known as the Aralkum Desert. 

At around 17,000 square miles (45,000 square kilometers), the Aralkum Desert is the world’s youngest desert, created entirely due to man-made disturbances. The desolate area has replaced a once vibrant fishing and tourist industry. With the climate mitigating effects of the Aral Sea diminished, winters are now colder and summers hotter.

The Aralkum Desert lies in the path of a powerful east-west airstream and these pollutants have been carried as far away as Antarctica.  Known as Black Blizzards, these powerful wind sorts carry dust pollutants from the Aral Sea over thousands of miles away; Aral dust has been found in the bloodstream of penguins in Antarctica, in the glaciers of Greenland, and in Norway’s forests.

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When grains of sand pile up to form a mound or ridge, it is called a sand dune. Dunes are usually formed by wind blowing the sand in one direction. They can be of various shapes and sizes, including crescents, stars, and long ridges called seifs.

Sand dunes are some of nature’s most scintillating creations. These eye-catching land masses are found around the globe in different climatic conditions. They are not only limited to deserts, but can form in any landscape on the earth’s surface provided the conditions are right. Every sand dune is formed as a result of the interaction between the wind and soil in the form of sand grains. There are many ways thrill seekers can explore sand dunes, for example, sliding down the dunes, Bird viewing in wetlands, skiing, sand boarding or just sledging on the sand slopes. Sky divers or those on airplanes experience the true beauty of sand dunes.

A Sand Dune is a small ridge of hill of sand found in a desert or on top of a beach. When they form on a beach, they are typically above the normal maximum reach of the waves. They form from millions of finely divided sand particles that are blown by the wind and get deposited against some obstacle such as a piece of drift wood, bush or rock.

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Today’s deserts were not always arid lands, and their soil was held in place by plants and trees. But when vegetation dies out, the soil is exposed to erosion. Gradually, the lighter clay and dried organic particles are blown away by the wind, leaving behind grains of sand made up of small particles from eroded rocks.

Sand consists of small particles of larger rock that’s been eroded. But erosion doesn’t happen fast enough in arid environments to be the only cause of desert sand.

Nearly all sand in deserts came from somewhere else – sometimes hundreds of kilometers away. This sand was washed in by rivers or streams in distant, less arid times – often before the area became a desert.

Once a region becomes arid, there’s no vegetation or water to hold the soil down. Then the wind takes over and blows away the finer particles of clay and dried organic matter. What’s left is desert sand.

Finding the exact origin – the source rock – of a desert’s sand can be difficult. Scientists might look for the origin by following dried riverbeds upstream or by tracking the “footprints” that sand left as it traveled – for example, streaks on the faces of boulders left behind by blowing sand in centuries past.

Sometimes an entire desert has migrated due to movement of Earth’s huge overlying land plates. When that’s happened, pieces of the same source rock are sometimes discovered on both sides of a fault line. When scientists identify a potential source rock, they match it to sand grains by its age and composition.

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Deserts are dry for different reasons depending on where they are. Winds in sub-tropical deserts, such as the Sahara in northern Africa, prevent rain clouds from forming. Coastal deserts, like the Atacama in Chile, get no rain, just a little moisture from fog. Death Valley, in California, USA, is a rain shadow desert on mountainsides that face away from rain-filled winds. The Gobi, in Mongolia, is an interior desert; rain-bearing winds cannot reach so far inland. Polar deserts, such as the Arctic and Antarctic, are dry because the water is locked as ice.

Areas that receive less than 25 centimeters (10 inches) of rain annually are called deserts. Deserts are dry with sparse vegetation. Landforms tend to have angular features because the lack of rain results in minimal chemical weathering, and flash floods create steep?walled scarps and gullies. There are few plants to protect the soil from the wind, so the soil is blown away to expose the rocky surface. Even in such a dry climate, most of the landforms are carved by the rare periods of heavy rainfall that result in flash floods, erosion, and sediment deposition.

Hot air rises at the equator, where the land receives the greatest amount of the sun’s radiation. Most of the world’s deserts are located near 30 degrees north latitude and 30 degrees south latitude, where the heated equatorial air begins to descend. The descending air is dense and begins to warm again, evaporating large amounts of water from the land surface. The resulting climate is very dry.

Other deserts are located in the rain shadows of mountain ranges. As moist air passes over a mountain range, it expands and cools, precipitating most of its moisture as it rises. As it sweeps down the other side of the mountain range, it warms and compresses, causing high evaporation rates and shedding little rain. Many of the deserts in the southwestern United States are the result of rain shadows.

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Deserts can have extremes in temperature. Daytime may get as hot as 54°C in hot deserts, while at night, dryness and lack of cloud cover cause a sharp drop in temperature, and it can get as cold as 4°C.

As extremes of nature go, the marked contrast in temperature of a desert during the day and at night is one of the most impressive. Searing heat can torture human occupants. After dark, the problem is reversed, and a winter jacket might prove useful. On average, temperatures in Africa’s Sahara Desert can swing an astounding 75 degrees in 24 hours, rising to an average 100°F with the sun out and plummeting to 25°F after it sets.

When the sun is out, sand proves to be an effective distributor of heat, reflecting it back into the air. But it’s not very good at retaining heat. Once the sun goes down, heat from the sand is released quickly.

The thing that could help retain warm air overnight is humidity, but deserts don’t have much of that. Water vapor in the air traps heat: Think of it like an insulating blanket, preventing either heat or cold from dispersing into the air. When the heat source is taken away, that vapor will retain it for long periods. Without sun or humidity, daytime heat isn’t being held anywhere, and the desert will cool rapidly.

Humidity is also why deserts can feel hotter than other places even though the temperature is the same. The water vapor needs lots of solar energy to heat up, while a dry climate takes that energy head-on.

All of this happens quickly because of that lack of humidity. Just as warm air escapes when night falls, there’s no humidity to trap the chilly evening weather. When the sun rises, it’s back to scorching.

Other factors can come into play. Clouds that help moderate temperature and wind can both help keep temperatures from dropping. But generally, you’ll roast in a desert and then freeze because the combination of sand and low humidity isn’t really suited for comfortable and consistent climates.

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Ice eggs are a rare phenomenon in which small pieces of ice are rolled over by wind and water. Chunks of ice break off from larger ice sheets in the sea and wash up on shore on the incoming tide or are pushed in by gusts of wind at the water’s surface. Waves strike the ice chunks as they travel, slowly eroding their jagged edges into smooth curves. Seawater sticks and freezes to the forming eggs, causing them to grow. Once the ice chunks reach the shore, the pounding waves smooth out any lingering sharp edges on their surfaces, leaving behind shiny “eggs”.

Given enough time, the frozen balls can grow to become boulder size. In 2016, giant snowballs washed up on a beach in Siberia, some measuring a metre (about 3 feet) across. An ice specialist from the Finnish Meteorological Institute has been quoted as saying ice balls are rare but not unprecedented, and occur about once a year on the Finnish coastline as conditions allow. They also appear on the American Great Lakes where they are called Ice balls.

Credit : Wikipedia 

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