The entire surface of the Earth consists of water and land. Moreover, the solid part accounts for only 29% of the total area of the planet. Yes, and that is indented by rivers, streams, streams, canals. 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 more correct to call 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 - for a long time remained a mystery. Today, geological science can explain a lot, in particular, why continents move.
What are they made of?
A huge granite-sedimentary block lying on the basalt 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 opposite part of the planet from the Pacific Ocean. In their structure, the continents are heterogeneous. They consist of:
- geosynclines (areas of folding);
- platforms (sustainable areas).
Answering the question of what the mainland is, it can be said that this is a large land mass washed by the ocean and consisting of mobile and stable sections.
The moving parts of the continents are folded zones that are thousands or even tens of thousands of kilometers long. An example of such a geosynclinal region is the Alpine-Himalayan belt, which stretches in the latitudinal direction across Eurasia. In the relief, folding is expressed by mountains and depressions.
Platforms are sedentary areas. These are stable, long-formed sections of the earth's crust. They are covered from above with a cover of sedimentary rocks, which hide all the irregularities of the foundation. Large plains are located in such areas of the earth's crust. An example is the East European Plain, which is located on the Russian platform.
Mainland drift
Nowadays, there are 6 continents. The largest of them is Eurasia, and then they are arranged in this order: Africa, North America, South America, Antarctica and the smallest - Australia.
But there was a period in the history of the Earth when there was only one supercontinent Pangea and he was washed by the waters of one Pantalassa 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 heyday.
About 200 million years ago, the ancient continent split into Laurasia and Gondwana. An ocean of Tethys formed between them. Laurasia left for the northern hemisphere, and Gondwana remained in the southern.
In turn, these two ancient continents, under the action of the motion of the mantle substance, also split into separate parts, which began to drift in different directions, gradually moving away from each other. So modern continents were formed, the outlines of which we know from the school bench.
Thus, any modern mainland is just a fragment of the ancient Pangea that existed in the distant past.
