As early as 1926, the American geophysicist Gutenberg noticed that the seismic velocity of the upper mantle at 100-200 km below the surface slowed down.

In 1955, he discovered that the wave velocity of the longitudinal wave was 6% lower than that of the Moholovich interface at a depth of 140 km below the ground.

In 1957, the Soviet seismologist Gorshkov further discovered that about 55-60 km below the Kuril Islands and Sakhalin, the longitudinal wave velocity of the earthquake decreased and the transverse wave disappeared.

These findings mean that the rocks there are in a molten state. According to the change of the seismic wave propagation velocity, the geologist divides the upper mantle into three layers: the uppermost layer is called the cover layer, the lower layer of the cover layer is the low-speed layer, and the lower layer of the low-speed layer is a uniform layer with relatively uniform seismic wave propagation velocity.

The middle low-velocity layer is a plastic-like, slowly flowing formation below the lithosphere, called the soft-flow layer, also known as the asthenosphere.

The current range is 100-220 km below the surface and 70-220 km in the ocean. Within this depth range, the temperature increase is greater than the pressure increase.

Some of the rocks are partially melted and have great plasticity, and the substances flow in the horizontal direction. The top and bottom interfaces of the soft layer are not completely defined, and there is no obvious interface with the lithosphere, which has the characteristics of gradual transition.

The formation of the asthenosphere is a long process of geological evolution. The thermal energy, water and volatile substances required for the production of the asthenosphere lava are mainly caused by the decay of radioactive elements and are released during the differentiation of the Earth’s circle.

When the released heat energy and light components rise to the bottom of the low temperature and rigid rock ring, they are gradually blocked by the lithosphere, which leads to the formation of a soft layer in the part.

Therefore, the formation of the soft layer is the development of the earth. The product of a certain stage. The soft layer has fluidity.

The hard rock plate “floats” on this fluid soft layer. The soft layer acts like a lubricant and can greatly reduce the friction between the rock mass and the mantle.

The lithosphere floats on the soft aquifer, and the modern plate tectonic movement is carried out on it.