October 23, 2021
Plate tectonics (板構造論, plate tectonics) is a geological theory that explains continental drift. Plate tectonics evolved from explaining 'continental drift', and most scientists in this field now accept plate tectonics. According to plate tectonics, the outermost part of the Earth's interior consists of two layers: the lithosphere and the asthenosphere. The lithosphere is composed of the crust and the uppermost mantle that has cooled and hardened, and the softer sphere below is composed of a viscous and fluid mantle. For millions of years or more, the mantle behaves like an extremely viscous liquid, but behaves like an elastic body for short-duration forces, such as the propagation of seismic waves. The lithosphere floats above the soft sphere. The lithosphere is divided into several pieces called plates. The ten major plates are the African, Antarctic, Australian, Eurasian, North American, South American, Pacific, Cocos, Nazca, and Indian plates. In addition to these, a number of small plates move with each other to form three types of boundaries: convergent boundaries, divergent boundaries, and conservation boundaries. Earthquakes, volcanoes, orogenic movements, and trenches occur mostly along plate boundaries. Plate tectonics started from two different theories: the continental drift theory, which began to be recognized in the early 20th century, and the ocean floor expansion theory, which began to be known in the 1960s. Plate tectonics was developed in the late 1960s, and after that, it revolutionized earth science and was accepted by almost all scientists. It is accepted as a revolutionary theory comparable to the periodic table of chemistry, the discovery of the genetic code in biology, and quantum mechanics in physics.