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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