Category Our World

When do rivers begin?

There are two main ways in which rivers begin. Some rivers start when a natural spring releases water from underground. These are often small trickles of water which develop into small streams. In turn these streams increase in size until they are acknowledged as rivers.

Other rivers begin when persistent rain makes a groove or a channel in a piece of land. As more and more rain falls into this channel, a flow of water slowly begins. Just like the springs, a stream can soon develop into a river.

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When rivers reach land close to sea level, they begin to meander, forming a snake-like shape on the land. This is caused by the gradual dropping of the sediment it carries where the flow is weak.

 

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When does the water cycle stop?

Water cycles demonstrate how water evaporates from the oceans then rises in the air to form clouds. In areas of low pressure, the clouds release the water as rain. This falls into the oceans again, or falls onto the land where it gradually works its way back into the oceans via streams and rivers. This is a continual, cyclical process.

However, in some areas of the world where there is no rainfall for long periods of time, local water cycles do stop. When one event in the cycle fails to happen, the cycle breaks down.

But water can neither be created nor destroyed – it will always exist in some form. If you consider the world as a whole, with one big water cycle, the processes involved are always occurring somewhere: this cycle never stops.

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Too much rainwater can have disastrous effects on the land. Flooding washes away fertile soil, and begins eroding the land.

 

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When was the longest drought?

The longest drought in recorded history took place in Calama, in the Atacama desert of Northern Chile.  For four centuries, beginning in 1571, no rain fell in the area. It was not until 1971 that rainfall was first recorded again. The Atacama desert, which lies between the Andes and the Pacific ocean, is recognized as the driest place in the world.

The Atacama desert remains so dry because it lies in a region where there is constant high air pressure, with little air movement, and with few clouds overhead.

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Some people believe that animals are good predictors of weather. One such belief is that if cows are standing in their field, then dry weather is expected. If they are lying down, however, rain is expected.

 

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When does water become salty?

Water becomes salty when minerals (including salts) dissolve into it. This process begins when rainwater falls on the land and erodes rock. The minerals found in rock are dissolved into the rainwater.

These dissolved minerals in the rainwater enter streams and rivers, gradually working their way into the seas and oceans.

This is a process which is constantly taking place, so the level and concentration of salt in the oceans and seas is always increasing. Some of the minerals are consumed by organisms in the water, but the vast majority of them make up the saltiness of the water.

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Lighthouses were built to worn ships at sea that they were approaching land and rocky water. Their beam of light across the waves made travelling by boat much safer.

 

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When was the longest heatwave?

The longest heatwave ever recorded was in Marble Bar, Australia when the temperature stayed above 38 . It lasted for 162 days from 23 October 1923 to 7 April 1924.

The highest average annual temperature recorded is 34.4  in Dallol, Ethiopia.

The lowest recorded temperature (outside of the poles) was -68  in Verkhoyansk, Siberia, on 6 February 1933.

The lowest average annual temperature of -56.6  was recorded at the Plateau Station, Antarctica.

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Some living things have adapted to survive long periods of time without water. Plants such as cacti have the ability to conserve water. They also minimize water loss as they have no leaves, and photosynthesis takes place in the stem. They have roots which reach deep into the ground for water.

 

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When do we see mirages?

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 an oasis or town on the horizon, but in reality it is not there.

Under certain conditions, such as a stretch of pavement or desert air heated by intense sunshine, the air rapidly cools with elevation and therefore increases in density and refractive power. Sunlight reflected downward from the top of an object. When the sky is the object of the mirage, the land is mistaken for a lake or sheet of water.

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About one-third of the world’s land surface is covered by desert. Deserts are found wherever there is too little water to allow much plant life to grow. Salt deserts form when shallow seas and lakes dry up, leaving a deposit of smooth salt.

 

Picture Credit : Google