theory of lithospheric plates - one of the most interesting geographical science.Hypothesis mobilism (otherwise - continental drift), once forgotten, is now again revived by the discovery of the poles of the magnetic anomalies of variable sign that symmetric mid-ocean ridges (their axis), the primary magnetization, and change over time, the position of the magnetic poles.
repeatedly confirmed the notion of expanding ocean floor along the axes of mid-oceanic ridges to peripheral areas has been obtained in the course of many years of research, as well as a result of deep-water drilling.The considerable contribution to research and development of the idea of continental drift (mobilism) made seismologists.Through their research, it was possible to clarify the procedure for the distribution of seismic zones on the Earth's surface.It turned out that these extended area, but rather narrow: they pass near major arcs on the edges of continents and mid-oceanic ridges.
Plate tectonics
mobilism This hypothesis is called "Plate tectonics".There are not a lot - a total of eight major and a dozen smaller ones.The latter is also called microplates.The largest plate located within the Pacific, they are a thin, light-permeable oceanic crust.In the Indo-Australian, Antarctic, African, South American, North American and Eurasian plates continental crust.Lithosphere plates have different borders (edges) and slowly moved across the planet's surface.When lithospheric plates apart, edges are divergent: Expenses plate form rift zone (crack), which receives the mantle substance.On the bottom surface, it hardens, and there is capacity of the oceanic crust.All new and new mantle material fed into the rift zone, expands it and makes the plate to move Where they move apart, the ocean is formed, and its dimensions are constantly increasing.This type of boundaries now available along the axes of mid-oceanic ridges and fixed rift cracks.
Convergent borders are formed when the lithospheric plates converge.When they approach in the areas of contact occur fairly complex processes, among which there are two main scientists.The first is that the collision of continental plates and oceanic one of them sinks into the mantle, and it is accompanied by breaking and warping.In the area of the collision takes place deep earthquakes.After hitting the plate into the mantle, it is partially melted: its most light components after melting once again rise to the surface, becoming volcanic eruptions.A more dense components, gradually sinking into the mantle, descend down to the core boundaries.It thus formed Pacific Ring of Fire.
When two continental plates occur ridging.This can be seen in the icing, the ice floes, and advancing facing each other, razdrablivayutsya.When lithospheric plates collide, they are compressed, and formed on the edges of major mountain structures.
theory of lithospheric plates
Through years and numerous observations, geophysics established average speed of the lithospheric plates.The District was formed in a collision of Hindustan and the African plate with the Eurasian plate Alpine-Himalayan belt compression rate of convergence between them is up to 0.6 cm / yr in the Himalayas and Pamir, and 0.5 cm / year in Gibraltar.
theory of lithospheric plates found that Europe is now moving away from North America at a rate of about 5 cm / yr.But Australia "sails" of Antarctica at a speed of about 14 cm / year.The highest rate in oceanic plates - they are 4-7 times higher than the rates of continental.Fastest - the Pacific plate and the slowest - Eurasian.
