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 because of 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 plate movements and, therefore, the world.
However, scientists have found that it can not be the only mechanism that over millions of years the continents move. Although the main convection process that controls plate tectonics, is known, many details remain a mystery. First of all: how to model the tectonics of the Earth "separate" from the asthenosphere, lithosphere plates, so they can slide on it?
There are many theories, such as stipulating that 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, such as under the Pacific plate. Thus, this theory can not explain the motion of plates in the regions where the "grease" is not. The discovery was made using the shear wave (S-wave), which are generated during earthquakes and spread 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 oceans, but also had a significant impact on the climate, 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 sign of her tectonics also been observed. One theory suggests that in the absence of water, the asthenosphere is more rigid and Venus can not cause drift of tectonic plates. Apparently, the warm core of the planet is given in some other way, perhaps by periodic global volcanic eruptions.