the vogla don and ural rivers follow though whitch country

#The vogla don and ural rivers follow though whitch country series

Geologists call this supercontinent Pangaea, which means “all lands” in Greek. Millions of years of continuous tectonic activity changed their positions, and by 240 million years ago, almost all of the world’s land was joined in a single, huge continent. About 480 million years ago, most continents were scattered chunks of land lying along or south of the Equator. The continents have not always been where they are today. Wandering Continents If you could visit Earth as it was millions of years ago, it would look very different. For this reason, continental crust is much, much older than oceanic crust. Oceanic crust is constantly being recycled in the mantle. In subduction zones, where tectonic plates interact with each other, oceanic crust always subducts beneath continental crust. Continental crust is much lighter than oceanic crust. The building of volcanic islands and continental material through plate tectonics is a process that continues today. This made even larger landmasses-the first continents. Their material fused with that of islands on the neighboring plate. When plates carrying islands subducted, the islands themselves did not descend into the mantle. Over time, these islands grew bigger, partly as the result of more lava flows and partly from the buildup of material scraped off descending plates. Gradually, the igneous rock built up into small volcanic islands above the surface of the ocean. When the lava cooled, it hardened into igneous rock. Called magma, it rose through the overlying plate and burst out as lava. When heavy oceanic crust subducted toward the mantle, it melted in the mantle’s intense heat. During subduction, plates collide, and the edge of one plate slides beneath the edge of another. Scientists theorize that this material built up along the boundaries of tectonic plates during a process called subduction. Only a small fraction of the crust was made up of continental material. At that time, a primitive ocean covered Earth. Studies of rocks found in ancient areas of North America have revealed that the oldest known pieces of the continents began to form nearly four billion years ago, soon after Earth itself formed. Geologists believe the interaction of the plates, a process called plate tectonics, contributed to the creation of continents. Today, tectonic plates continue to slowly slide around the surface, just as they have been doing for hundreds of millions of years. The heat from inside the earth causes the plates to slide around on the molten mantle. The crust and the top portion of the mantle form a rigid shell around the earth that is broken up into huge sections called tectonic plates. Eventually, the earth came to have three main layers: the core, the mantle, and the crust. Heavier material sank toward Earth’s center. As the heat increased, some of Earth’s rocky materials melted and rose to the surface, where they cooled and formed a crust. The continuous smashing of space debris and the pull of gravity made the inside of Earth heat up.

Building the Continents The Earth formed 4.6 billion years ago from a great, swirling cloud of dust and gas.

An imaginary line, running from the northern Ural Mountains in Russia south to the Caspian and Black Seas, separates Europe, to the west, from Asia, to the east. Because of this, most geographers divide Eurasia into Europe and Asia. But linguistically and ethnically, the areas of Asia and Europe are distinct. The continents of Europe and Asia, for example, are actually part of a single, enormous piece of land called Eurasia. To geographers, continents are also culturally distinct. A continental shelf is part of the ocean, but also part of the continent. A continental shelf is a gently sloping area that extends outward from the beach far into the ocean. Continents are defined by their continental shelves. Coastlines, however, do not indicate the actual boundaries of the continents.

#The vogla don and ural rivers follow though whitch country series

Asia, the largest continent, has the longest series of coastlines. All continents border at least one ocean. The area of the ocean is more than double the area of all the continents combined. The ocean covers almost three-fourths of Earth. A very small portion of the total land area is made up of islands that are not considered physical parts of continents. Continents make up most-but not all-of Earth’s land surface.

Together, the continents add up to about 148 million square kilometers (57 million square miles) of land. Greenland and all the islands in the Caribbean Sea are usually considered part of North America. Japan, for instance, is part of the continent of Asia. When geographers identify a continent, they usually include all the islands associated with it. The continents are, from largest to smallest: Asia, Africa, North America, South America, Ant arctica, Europe, and Australia. A continent is one of Earth’s seven main divisions of land.