The entire surface of the Earth consists of water and land.Moreover, the hard part accounts for only 29% of the total area of the planet. Yes, and that is indented by rivers, rivulets, streams, channels. And how many on land there are swamps, ponds and lakes - and not count, since some of them periodically disappear, then reappear. Perhaps our planet would be better called Water.
All land is divided into separate continents.They are also called continents. What is the mainland, what is the history of its origin and development - has long remained a mystery. Today, geological science can explain a lot, in particular, why continents are moving.
A huge granite-sedimentary block lying onBasaltic layer, about 40 kilometers thick - this is what the mainland is. Today, there are six continents, and they are located on the Earth's surface very unevenly, grouped in the part of the planet opposite to the Pacific Ocean. The structure of the continents is heterogeneous. They consist of:
Answering the question of what a continent is, we can say that this is a large land mass, washed by the ocean and consisting of moving and stable parts.
The moving parts of the continents are folded.zones extended in length for thousands, or even tens of thousands of kilometers. An example of such a geosynclinal region is the Alpine-Himalayan belt, stretching in the latitudinal direction through the whole of Eurasia. In the relief, folding is expressed by mountains and valleys.
Platforms - inactive areas.These are stable, long-formed areas of the earth's crust. They are covered on top with a cover of sedimentary rocks that hide all the irregularities of the foundation. On such areas of the earth's crust are large plains. An example is the East European Plain, which is located on the Russian platform.
Continental drift
In our time there are 6 continents.The largest of them is Eurasia, and then they are located in this order: Africa, North America, South America, Antarctica and the smallest - Australia.
But there was a period in the history of the Earth whenthere was only one super-continent Pangea and it was washed by the waters of the same Pantalass ocean. What is the mainland of the Mesozoic era? This is a huge land, equal in size to all of today's continents combined. Pangea was covered with lush vegetation, among which dinosaurs roamed freely. It was their kingdom and the heyday.
About 200 million years ago, the ancient continent split into Laurasia and Gondwana. Between them formed the ocean Tethys. Laurasia went to the northern hemisphere, while Gondwana remained in the southern.
In turn, these two ancient continents underthe action of the motion of the substance of the mantle also split into separate parts, which began to drift in different directions, gradually moving away from each other. This is how the modern continents were formed, the outlines of which are known to us from school.
Thus, any modern continent is just a fragment of the ancient Pangea, which existed in the distant past.
