Earth is the only planet in our solar system that is definitely known to contain liquid water. The ocean makes all life on Earth possible, and makes the planet appear blue when viewed from space. It contains about 1.35 billion cubic kilometers (324 million cubic miles) of water, which is about 97 percent of all the water on Earth. The ocean covers 70 percent of Earth's surface. Today, the theory is almost universally accepted.This article is also available in Spanish. Wilson’s explanation gave further support to plate tectonics. As the plate moves over the hot spot, one volcanic island after another is formed. At those places, magma forces its way upward through the moving plate of the sea floor. He proposed that volcanic island chains, like the Hawaiian Islands, are created by fixed “hot spots” in the mantle. How could this be explained? This question was finally answered in 1963 by a Canadian geologist, John Tuzo Wilson. There was one nagging question with the plate tectonics theory: Most volcanoes are found above subduction zones, but some form far away from these plate boundaries. Magnetic data from the ocean floor and the relatively young age of oceanic crust supported Hess’s hypothesis of seafloor spreading. Millions of years later, the crust would disappear into ocean trenches at places called subduction zones and cycle back into Earth. As it came to the surface, the rock cooled, making new crust and spreading the seafloor away from the ridge in a conveyer-belt motion. An American geologist named Harry Hess proposed that these ridges were the result of molten rock rising from the asthenosphere. Maps of the ocean floor showed a massive undersea mountain range that almost circled the entire Earth. In addition, South America and Africa looked like they could fit together like puzzle pieces.ĭespite being dismissed at first, the theory gained steam in the 1950s and 1960s as new data began to support the idea of continental drift. To support his theory, Wegener pointed to matching rock formations and similar fossils in Brazil and West Africa. The continents we see today are fragments of that supercontinent. He suggested that 200 million years ago, a supercontinent he called Pangaea began to break into pieces, its parts moving away from one another. Wegener published two articles about a concept called continental drift in 1912. However, a German scientist named Alfred Wegener changed the scientific debate. The idea that continents moved over time had been proposed before the 20th century. This interaction of tectonic plates is responsible for many different geological formations such as the Himalaya mountain range in Asia, the East African Rift, and the San Andreas Fault in California, United States. Due to the convection of the asthenosphere and lithosphere, the plates move relative to each other at different rates, from two to 15 centimeters (one to six inches) per year. These plates lie on top of a partially molten layer of rock called the asthenosphere. In plate tectonics, Earth’s outermost layer, or lithosphere-made up of the crust and upper mantle-is broken into large rocky plates. The theory, which solidified in the 1960s, transformed the earth sciences by explaining many phenomena, including mountain building events, volcanoes, and earthquakes. Plate tectonics is a scientific theory that explains how major landforms are created as a result of Earth’s subterranean movements.
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