March 28. A team of scientists funded by NASA found that the asthenosphere of the Earth is not the main reason for the movement of continents. Science once again have to revise many of the details of plate tectonics, which are changing the face of our planet.
Asthenosphere — a layer of partially molten rock at a depth of 35-120 km. The outer layer of the Earth (lithosphere) is divided into many tectonic plates. Under the ocean lithosphere is relatively thin (about 100 km), and thicker under the continents (320 km). Beneath the lithosphere is the asthenosphere, plastic and partly due to the heat of the molten core of the earth. Until now it was thought that the convection and viscous "Grease" asthenosphere are the main causes of plate movements and thus the world.
However, scientists have found that it can not be the only mechanism that over millions of years, moving continents. Although the main convection process driving plate tectonics, is known, many details remain a mystery. First of all: how to model the tectonics of the Earth "separate" plates from the asthenosphere so they can slide on it?
There are many theories, such as stipulating that the molten asthenosphere layer helps keep them lubricated, allowing the lithospheric plates slide and move continents. However, scientists have found that a layer of "Grease" is present only in certain regions, for example, under the Pacific plate. Thus, this theory can not explain the movement of plates in the regions where the "grease" no. The discovery was made by means of shear-wave (S-wave), which are generated during earthquakes propagate through the entire planet. This allows you to approximate the composition and density of rocks at great depths.
Understanding of plate tectonics is very important because it not only changed the face of the land and the oceans, but also significantly affected the climate of the planet, redirecting ocean currents. In addition, the tectonics of the Earth can help us to study the evolution of other rocky planets, such as Venus. As you know, this planet has oceans, and no evidence of tectonics on it is also not observed. One theory suggests that in the absence of water, the asthenosphere of Venus harder and not cause drift of the lithospheric plates. Apparently, the warm core of the planet is given in some other way, perhaps by periodic global volcanic eruptions.