In collaboration with Tohoku University, Kenichi Hirauchi, a lecturer at Shizuoka University, and Kumi Fukushima, a second-year master's student, collaborate with Tohoku University. It was clarified experimentally.It is an important achievement to elucidate the mechanism of plate tectonics.
The surface of the earth is covered with dozens of hard plate-shaped rocks (plates) with a thickness of several tens of kilometers, and it is moving little by little due to mantle convection inside the earth.Geological phenomena such as earthquakes that occur due to contact between plates and subduction are called plate tectonics and do not exist outside the earth.Plate subduction occurs along the fault between the plates, but it is estimated that the fault strength is not low enough to cause subduction.Therefore, it was said that the mechanical fragility of hydrous minerals formed by reacting with water was involved, but no concrete verification was made.
The research group conducted a hydrothermal deformation experiment of "peridotite", which is a plate constituent rock near the fault, under the temperature and pressure conditions corresponding to the deep part of the ocean plate (depth 20 km).As a result, peridotite and water reacted to form hydrous minerals called talc, and the rock strength dramatically decreased as the deformation progressed.The strike-slip fault that exists at the plate boundary is called a transform fault, and it is said that seawater infiltrates into the transform fault in the deep part, causing a decrease in strength due to rock-water reactions and starting subduction of the ocean plate.
From this result, it can be explained that the reason why plate tectonics is not seen outside the earth is that it is caused by the existence of the ocean on the surface of the planet.In the future, it will be necessary to verify how plate tectonics began in the early stages of Earth formation.
