Category Our World

When was the Mediterranean a dry basin?

We know the Mediterranean today as a huge sea off the coast of Europe. However, the Mediterranean was not always like that. Approximately 5 million years ago, the Mediterranean was a dry basin. Movements in the Earth’s crust opened up the Gibraltar Straits between the continental areas which are now Africa and Europe. The Atlantic Ocean would have poured through this new opening into the dry basin. The result would have been an enormous waterfall, nearly 800 metres high. So much water poured in from the Atlantic that the Mediterranean Sea was created in only a few years.

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Of course, through time the shape of the continents will continue to change, and new seas will form; some could even join together. 


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When was the earth formed?

No one knows for certain when the Earth was formed exactly. However, scientists have reasoned that it probably formed about 6,000 million years ago.

The most scientific reasoning for the creation of Earth is that it began as a huge ball of hot gases which cooled to form the planet. Seas of dissolved chemicals would have covered the land, and the air would have been an atmosphere of different gases. The atmosphere was thought to have consisted of swirling gaseous clouds which most likely caused huge electrical storms.

The poisonous gases in the atmosphere must have reacted to produce oxygen, which triggered off the first beginnings of life on Earth.

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As Earth cooled down, it gave off clouds of steam and gas. The moisture in these clouds eventually turned to rain, which formed the first seas.

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When does the snow line move?

Snow lines are clearly visible on mountains. They mark out the area above which a mountain is permanently covered in snow.

The highest points of a mountain are much colder than the lower points. The snow which falls on the higher regions never thaws because it is so cold. In the summer, however, the warmer weather begins to melt some of the snow. This causes the snow line to move up the mountain.

As the summer months pass by and the winter months return, the snow line moves further down the mountain once again.

In colder regions, the snow line is close to ground level, but where the air is warmer, the snow line is closer to the Equator.

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Mountains such as the Rockies in South America, do not see a dramatic movement in the snow line. This is because they are so high up. The climate is very cold in winter and the summers are short-lived.


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When does water turn into snow?

Water turns into snow at temperature above -40 . Snow forms when water in clouds freezes into tiny ice crystals. This moist air freezes around minute dust particles or chemical substances floating in the clouds. These particles become the core, or the nucleus, of each crystal. Snow crystals grow in size when more water crystallizes around a particular nucleus. This happens more if the air is humid.

Snowflakes are formed when a number of crystals join together in clusters. The structure of snowflakes is often a beautiful, hexagonal form. It is believed that no two snowflakes can be identical. These fall from the clouds onto land as snow.

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Eskimos live in houses made completely of snow called igloos. The Eskimos cut away blocks of snow and build the igloo as though they are bricks. Because where they are built is so cold, the igloos do not melt.


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When is climax vegetation achieved?

When vegetation first starts growing in newly formed soil, it is disadvantage because the soil will not be nutrient-rich. As the plants die, they enrich the soil, allowing more plants to take advantage of this. As the soil gets older, it has gleaned more and more nutrients from dead plants – and more and more plants are able to grow successfully in the soil. Climax vegetation occurs when the vegetation is totally suited to soil. In reality, this can never last permanently due to the ever-changing environment.

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Rainforests have developed in areas where the soil is very fertile and where there is a great deal of rainfall. The varied vegetation suggests the soil is extremely nutrient-rich.


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When does the appearance of soil change?

Soil changes its appearance when the biological or chemical make-up of it varies. For example, red soil is found in areas where there is a high content of iron compounds. Oxisol is a good example of this; it is found in tropical regions where both chemical and biological activities are high.

If you thought that all soils are brown, think again. Soil colours range from black to red to white. Sometimes it can even be blue! Soil colour mostly comes from organic matter and iron. Topsoil is often dark because of organic matter. An even, single colour indicates the soil is well drained. In contrast, rusty spots and grey patches (sometimes even a light blue in colour) indicate poor drainage.

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Soil is not just a single, consistent layer of material.


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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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