entire surface of the Earth is made up of water and land.And on the part of the firm accounts for only 29% of the total area of the planet.Yes, and that is dissected by rivers, rivulets, streams, channels.And how much land is available in the swamps, ponds and lakes - and did not count, because some of them periodically disappear, then reappear.Perhaps our planet properly be called water.
All land is divided into separate continents.They are also called even continents.What is the mainland, what is the history of its origin and development - a long time remained a mystery.Today, geological science has a lot to explain, in particular why the continents move.
What they consist
Huge granite sedimentary boulder lying on the basalt layer thickness of about 40 kilometers - that's what the continent.Today there are six continents, and are located on the Earth's surface is very uneven, grouped in the opposite from the Pacific side of the planet.The structure of the continents uniform.They consist of:
- geosynclines (folding areas);
- platforms (stable area).
Responding to a question about what the continent, we can say that this is a large amount of land, washed by the ocean and consists of mobile and stable areas.
moving parts continents - is folded zones, extended in length by thousands, or even tens of thousands of kilometers.An example of this can serve as a geosynclinal region Alpine-Himalayan belt, which stretches to the east-west direction across Eurasia.The relief expressed by folding mountains and valleys.
Platforms - slow-moving field.This stable, long-formed sections of the Earth's crust.They are covered with a cover on top of sedimentary rocks, which hide all the irregularities of the foundation.At such sites, the earth's crust are large plains.An example is the East European Plain, which is located on the Russian platform.
drift
Nowadays there are 6 continents.The largest of these is Eurasia, and then they settled in the following order: Africa, North America, South America, Antarctica, and the smallest - Australia.
But there was in Earth's history a time when there was only one supercontinent Pangea, and washed by the waters of the ocean, he Panthalassa.What is the Mesozoic era of the continent?This is a huge land, the size of which is equal to all of today's continents put together.Pangea was covered with lush vegetation, among which the dinosaurs roamed freely.It was their kingdom, and during flowering.
About 200 million years ago, ancient continent split into Laurasia and Gondwana.Between them formed Tethys Ocean.Laurasia gone to the northern hemisphere and Gondwana in the south remained.
In turn, these two ancient continent under the influence of the motion of the mantle is also split into separate parts, which were drifting apart, gradually moving away from each other.This is how the modern continents, the outlines of which are known to us from school.
Thus, any modern mainland - it's just a fragment of the ancient Pangea that existed in the distant past.
