History of plate tectonics

Plate tectonics theory has made its debut in 1915, when Alfred Wegener proposed his theory of "continental drift." Wegener proposed that the continents through the crust of the ocean basins, which explains why many coastal contours (such as South America and Africa) as they would look together like a puzzle plowed. Wegener was not the first identified this puzzle-like continents (Magellan and other researchers also notice them on their cards), but it was understood among the first that the Earth's surface has changed over time, and that the continents separated from each other today at some point have collected in the past.
The paleontologists also found that fossils of similar species on the continent, which now by the great geographic distance from each other separately recorded. Paleoclimatology, the examination of the past found the earth's climate concerns, the glaciers that covered much of the world who are now separated by great geographical distances. These observations suggest that the lithosphere of the earth was moving through geological time.

Wegener's ideas were very controversial because it has not had an explanation for why the continents moved, so that observational data available to them. At the time, geologists have believed that the properties of the earth the result of the earth, which are characterized by cycles of heating and cooling, expansion and contraction of the land masses causes. People, the so-called anti-mobilistation believe. The mobilistation were in the opposite camp, and supports the ideas of Wegener, because many of them have seen the evidence of the continental movement, especially in the Alps.
Although Wegener's "continental drift" theory was disproved later, he was one of the first times that the idea of vertical crustal movements of the scientific community was presented, and they laid the foundation for development of modern plate tectonics. Over the years more and more evidence has been found to the idea that the plates are constantly moving to assist in geological time.
Palaeomagnetic studies that have investigated the past of the magnetic field of the earth showed that the magnetic north pole to walk in the world seems. This means that either the plates were in motion, or the North Pole. Since the North Pole is defined, essentially, except during periods of magnetic reversal, the evidence strongly supports the concept of plate tectonics.
After the Second World War, more evidence has been found, which supports the theory of plate tectonics. In the 1960s, a vast world of seismometers have been installed to monitor nuclear tests, and these instruments has revealed a surprising phenomenon geology. It was found that earthquakes, volcanoes and other geological features are aligned along most significant active belts around the world, and such bands defined the edges of tectonic plates.
In addition, paleomagnetic studies, a striped pattern of magnetic reversals have been found in the crust of ocean basins. Basalt contains a good amount of magnetic mineral called magnetite. If the lava cools spreading centers in the forms and the oceans, these minerals align with the North Pole. The Earth has undegone several magnetic reversals in the past in which the North and South Pole for a period of time be reversed. If geologists and geophysicists have discovered that the crust in the ocean these occasions he was even more positive evidence that the lithosphere has been recorded in motion, otherwise there would be no scratches "normal and reverse polarity crust.
These are some of the last pieces of the puzzle that the development of modern plate tectonic theory LED. Since its emergence in the 1960s, plate tectonics theory has widespread acceptance as the model of the Earth derived processes.

Internal Structure Of Earth

Geophysics, the study of the physics of the earth, led to many important discoveries about the earth and its composition. Seismic studies of the Earth, have revealed new information about Earth's interior, which helped invent the theory of plate tectonics.
Geophysical investigations have brought to light that the Earth has a number of layers. Each of these layers has its own characteristics. The outer layer of the earth's surface. It includes the continents and made the sea. The crust has a variable thickness, with 35-70 km of thick dick in the world and 50-10 km in the sea. The surface consists mainly of alumina-silicates.
The next layer is the mantle, mainly of silicates of magnesium, iron compound. It is about 2900 km thick and is divided into upper and lower mantle. This is where most of the internal heat of the earth is located. Large convection cells of the mantle circulate heat and power rhythm of the earth.

The last layer is the core in the liquid outer core is separated and the solid inner core. The outer core is 2300 km thick and the inner core is 1200 km thick. The outer core is mainly an alloy of nickel-iron, while the inner core consists almost entirely of iron. Earth's magnetic field is assumed to be controlled by the liquid outer core.
The country is divided into layers on the mechanical properties and composition. The top layer is the lithosphere, the solid component of the earth's crust and upper mantle exists. The lithosphere is divided into several plates move towards each other, divided by tectonic forces. The lithosphere essentially floats above numbers on a semi-liquid layer as the asthenosphere. This layer allows the solid earth's crust move from the asthenosphere is much weaker than the lithosphere.