, 关于Wegeners Continental Drift Theory
Wegener’s Continental Drift Theory, first proposed by German scientist Alfred Wegener in the early 20th century, proposed that the continents had once been joined together and had since moved apart, an idea that contradicted long-held popular beliefs. Wegener noticed that the various continents of Earth fit together neatly like a puzzle, a fact previously noted by other scientists as far back as the late 1700s. He proposed that if the continents were moved back to their positions before they had drifted apart, they would fit together perfectly. Wegener also supported his theory with evidence of fossil plants and animals found in marine deposits on the edges of continents and similar species found on both sides of the Atlantic Ocean.
One of the major criticisms of Wegener’s theory was that it lacked an adequate explanation of how the Earths crust could move. Wegener attributed the movement of the continents to a process of convection currents occurring within the Earth’s mantle. He argued that these convection currents were caused by the heat generated by radioactive decay, resulting in a slow but steady drift of the continents from one position to another. The convection current hypothesis was later superseded by the theory of plate tectonics.
The plate tectonics theory explains the arc-shaped pattern of volcanic and seismic activity found along the ocean basins. According to this theory, the Earth’s plates are in constant motion, moving apart or colliding with each other in order to accommodate the increases or decreases in the Earth’s radius. These movements of the plates are driven by the convection currents present in the Earth’s mantle.
In addition to providing evidence for the movements of the Earth’s plates, the plate tectonics theory also explains the formation and break-up of supercontinents. Supercontinents are large, united land masses that form when a number of plates collide and merge. The best known of these is Pangaea, which is thought to have existed over 200 million years ago. This allowed plants and animals to migrate rapidly across the globe and gave rise to new evolutionary pressures and species. When the supercontinent eventually broke up into smaller continents, the various plants and animals found on each continent developed in isolation, resulting in new species forming and old species going extinct.
Wegener’s Continental Drift Theory was far ahead of its time and was widely rejected by the scientific community at the time due to its inadequate explanation of the mechanism of continental movement. However, with the rise of plate tectonics, which integrated many of the ideas of Wegener’s Continental Drift Theory into its explanation of the Earth’s movements, the idea of continental drift was eventually accepted and has since proven itself as an invaluable theory for understanding the geological processes of the Earth.
