Continental Drift Theory and Plate Tectonic Theory

In the early 20th century, German scientist Alfred Wegener published a book explaining his possibleness that the continental landmasses, far from being immovable, were drifting crosswise the Earth. He called this cause continental drift. Wegener noticed that the coasts of western Africa and eastern due south America looked like the edges of interlocking pieces of a jigsaw puzzle. He was not the first to notice this, but he was the first to formally shew evidence suggesting that the two continents had once been connected. Wegener was convinced that the two continents were once distinguish of an enormous, single landmass that had split a reveal.He knew that the two argonas had legion(predicate) geological and biological similarities. For example, fossils of the ancient reptile mesosaurus are only found in southern Africa and siemens America. Mesosaurus, a freshwater reptile only nonpareil meter (3. 3 feet) long, could not have swum the Atlantic Ocean. The presence of mesosaur us suggests a single habitat with many lakes and rivers. Wegener believed that all the continentsnot just Africa and South Americahad once been joined in a single supercontinent. This considerable ancient landmass is known as Pangaea, which means all lands in Greek.Pangaea existed about 240 one thousand thousand years ago. By about 200 million years ago, this supercontinent began breaking up. Over millions of years, Pangaea separated into pieces that moved away from one another. These pieces slowly assumed their present positions as the continents. PLATE TECTONIC surmise Plate architectonics is the theory that the outer rigid layer of the earth (the lithosphere) is divided into a couple of dozen main offices that move around across the earths surface congenator to severally other, like slabs of ice on a lake. There are seven or eight major plates and many minor plates.Where plates meet, their relative motion determines the type of boundary convergent, divergent, or transform . Earthquakes, activity, mountain-building, and oceanic trench formation occur along these plate boundaries. The lateral relative movement of the plates typically varies from zero to 100 mm annually. Tectonic plates are able to move because the Earths lithosphere has a higher strength and disdain density than the underlying asthenosphere. Plate movement is thought to be impelled by a combination of the motion of the seafloor away from the spreading ridgepole and drag, downward suction, at the subduction zones.Another explanation lies in the different forces generated by the rotation of the globe and the tidal forces of the Sun and the Moon. The relative importance of to individually one of these factors is unclear, and is still subject to debate. The geoscientific community accepted the theory after the concepts of seafloor were demonstrable in the late 1950s and early 1960s. Fun Facts * The highest mountain aim above sea level, the Himalayas, was formed 55 million years ago when the Eurasian and Indo-Australian continental plates converged.Due to ongoing convergence, the Himalayas, including Mount Everest, continue to stand out by approximately 2 centimeters (?1 inch) each year. * The Mid-Atlantic extend runs down the center of the Atlantic Ocean. Along its crest, the ridge has a intricate rift valley that, on average, is similar to the depth and width of the luxurious Canyon 1 to 3 kilometers (0. 6 -1. 8 miles) deep and 6. 5 to 29 kilometers (4-18 miles) wide. * Scientists are able to calculate average rates of tectonic plate movement for a given time period. These rates of movement range widely.For example, the rate of spreading at the Mid-Atlantic Ridge burn up Iceland is relatively slow, about 2. 5 centimeters (1 inch) per year. This is similar to the rate at which fingernails grow. The hurried known rate of plate movement, 15 centimeters (6 inches) per year, occurs on the East peaceful Rise in the South Pacific. SEAFLOOR SPREADING Seafloor spreading is a cognitive process of plate tectonics. New oceanic sauciness is created as large slabs of the Earths insolence split apart from each other and magma wells up to content the gap. The large slabs of rock that make up the Earths crust are called tectonic plates.As they slowly move away from each other beneath the ocean floor, hot magma from the Earths winding-sheet bubbles to the surface. This magma is then cooled by seawater. The new rock forms a new part of the Earths crust. Seafloor spreading occurs along mid-ocean ridgeslarge mountain ranges lift from the ocean floor. New bodies of water and even continents can be created with seafloor spreading. The Red Sea, for example, was created with seafloor spreading, as the African plate and the Arabian plate tear away from each other.Today, the northern Sinai Peninsula connects the Middle East (Asia) with join Africa. Eventually, geologists predict, seafloor spreading volition expand the Red Sea so that it will com pletely separate the two continents. . Seafloor spreading disproves an early part of the theory of continental drift. Continental drift was one of the first theories that the Earths crust was propellant and always in motion. Supporters of continental drift originally theorized that the continents moved (drifted) through unmoving oceans.Seafloor spreading proves that the ocean floor itself is the site of tectonic activity. Subduction is the mated of seafloor spreading. Subduction happens where tectonic plates crash into each other instead of spreading apart. In subduction zones, the edge of the heavier plate subducts, or slides, beneath the lighter one. It then melts hind end into the Earths mantle. Seafloor spreading creates new crust. Subduction destroys old crust. The two forces roughly balance each other, so the shape and diameter of the Earth remains constant.