The first geographical handwritten newspaper picture.
Continental drift theory of crustal movement
German meteorologist Wei Gena (1880 ~ 1930) put forward a geotectonic hypothesis in 19 12. He believed that there was only one huge joint ancient land in the world in the Late Paleozoic, which was called "Pangaea". In the Mesozoic era, due to tidal friction and the compression force of the poles to the equator, Pangu continent began to split, and the lighter granite continent drifted on the heavier basalt mantle, gradually forming today's land-sea pattern. He believes that the mountains on the earth are also the products of continental drift, and the Cordillera Mountains and the Andes Mountains are folded mountains formed by the extrusion of the basaltic basement of the Pacific Ocean when the American continent drifts westward. The island arc group on the eastern edge of Asia is a relic left by the westward drift of the mainland. The southern tip of Greenland, Florida, Tierra del Fuego and other twists and turns are the result of sliding friction falling off to the west; The east-west Alps, Himalayas and other major mountain ranges are the result of the mainland squeezing from the poles to the equator. According to the data at that time, Wei Gena demonstrated the theory of continental drift in detail from the aspects of geology, topography, paleontology, paleoclimate and geodesy. This hypothesis attracted the attention of geologists and geophysicists at that time. However, many scholars are skeptical about the mechanism and law of continental drift. Since 1950s, paleomagnetic research shows that the magnetic pole movement in geological history can only be reasonably explained by continental drift theory. Therefore, the theory of continental drift has been reborn.
Plate tectonic theory of crustal movement
In 196 1 and 1962, Dietz and Hertz of the United States put forward the submarine expansion theory. On this basis, in 1968, French geologist Le Pishun and others initiated the theory of plate tectonics, which has now become the most popular new theory in earth science.
Plate tectonic theory divides the global lithosphere into six plates: Eurasian plate, African plate, American plate, Pacific plate, Indian Ocean plate and Antarctic plate, and there are some small plates besides these six plates. Some sub-layer plates can also be drawn within the mainland. Between plates, straits or trenches and orogenic belts are boundaries respectively. Generally speaking, the crust inside the plate is relatively stable; The boundary between plates is a relatively active zone of the earth's crust, and its activity is mainly manifested in earthquakes, volcanoes, tension cracks, dislocations, magma rising, crustal subduction and so on. Volcanic and seismic activities in the world are almost all distributed near the plate boundary.
Plate theory holds that the earth's crust is alive and dead. Due to the expansion of the seabed, the ocean floor is constantly updated, while the mainland only moves with the expansion of the seabed. In the process of relative movement, the plates either split to both sides or collide with each other, thus forming the basic appearance of the earth's surface. For example, 300 million years ago, Europe and Africa were connected with North and South America, and then the Atlantic Ridge appeared, and the new oceanic crust was continuously formed around it and expanded to both sides, separating the above continents. In the past 70 million years, the Indian plate has been moving northward, colliding with the Eurasian plate and forming the Himalayas. The Rift Valley in East Africa is in the embryonic stage when the African continent begins to crack and new oceanic crust is produced. The Gulf of Aden in the Red Sea is the result of the extension of the crust on both sides, and it is in the infancy of the oceanic crust. The Mediterranean, as we know it, represents the last period of ocean development, and it is the ocean left over from the long-term evolution of the vast ancient Mediterranean.
As for the driving force of the plate, some people think that it is mantle convection, while others think that "hot spots" and "hot columns" in the mantle arch the lithosphere, making it slide downward under the action of gravity to push the plate to move. There are other theories, but there is no unified understanding.
Continental drift-submarine spreading-plate tectonics is a trilogy to deepen and develop human understanding of crustal movement.