Continental Movement by Plate Tectonics | artsocial.info
Jul 29, At the boundary between Earth's core and mantle at km depth there is an therefore, an influence of plate tectonics and mantle convection on Earth's is still needed for a better understanding of these relationships. Convection currents in the magma drive plate tectonics. It contrasts with the more rigid lithosphere, the outer shell of the Earth (0 ~ 70 km) that contains the. The term fault is used to describe the boundary between tectonic plates. the movement of tectonic plates is related to convection currents in the earth's mantle .
Mid-ocean ridges are the largest continuous geological features on Earth. They are tens of thousands of kilometers long, running through and connecting most of the ocean basins. Oceanographic data reveal that seafloor spreading is slowly widening the Atlantic ocean basin, the Red Sea, and the Gulf of California Fig.
The gradual process of seafloor spreading slowly pushes tectonic plates apart while generating new rock from cooled magma. Ocean floor rocks close to a mid-ocean ridge are not only younger than distant rocks, they also display consistent bands of magnetism based on their age Fig.PLATE TECTONICS
Geomagnetic reversal allows scientists to study the movement of ocean floors over time. Paleomagnetism is the study of magnetism in ancient rocks. In other words, the particles will point in the direction of the magnetic field present as the rock was cooling. Seafloor spreading gradually pushes tectonic plates apart at mid-ocean ridges.
When this happens, the opposite edge of these plates push against other tectonic plates. Subduction occurs when two tectonic plates meet and one moves underneath the other Fig. Oceanic crust is primarily composed of basalt, which makes it slightly denser than continental crust, which is composed primarily of granite. Because it is denser, when oceanic crust and continental crust meet, the oceanic crust slides below the continental crust.
This collision of oceanic crust on one plate with the continental crust of a second plate can result in the formation of volcanoes Fig. As the oceanic crust enters the mantle, pressure breaks the crustal rock, heat from friction melts it, and a pool of magma develops.
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This thick magma, called andesite lava, consists of a mixture of basalt from the oceanic crust and granite from the continental crust.
Forced by tremendous pressure, it eventually flows along weaker crustal channels toward the surface. The magma periodically breaks through the crust to form great, violently explosive composite volcanoes—steep-sided, cone-shaped mountains like those in the Andes at the margin of the South American Plate Fig.
Continental collision occurs when two plates carrying continents collide. Because continental crusts are composed of the same low-density material, one does not sink under the other. During collision, the crust moves upward, and the crustal material folds, buckles, and breaks Fig. This zone, where rock is soft enough to flow, is called the asthenosphere.
This means of heat transport--the cyclical movement of hot and cold material--is called convection. You can see an example of this in your kitchen by heating a pan of water to what is called a "rolling boil": Occasionally, however, masses of hotter-than-normal rock rise independently of the broad flow, like bubbles through a flowing stream.
These masses of very hot rock form rising columns with rounded tops, called plumes. Rock near the surface of Earth is so cold and at such low pressures that it cannot flow like mantle rock. So how does heat get through this rigid layer lithosphere, to the surface?
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One way is by conduction which describes heat flow in an iron pan held over a fire. The part of the pan over the flame gets hot first, followed by the handle, which is not over the flame. The heat in the handle came from the pan, but there was no movement of hot material from one part of the pan to another as in convection.
The metal in the pan and handle certainly didn't flow! The heat, which is vibrations of atoms in the solid pan, moves as a result of fast moving hot atoms bouncing off slow moving cool atoms, causing the slow atoms to move faster heat up.
So at the top of the asthenosphere, the hot rock flows along the bottom of the lithosphere, transferring its heat to the cold rocks by conduction. The heat then flows through to the surface, again by conduction. Everyday examples of convection in liquids include lava lamps or water heating on a stove. But the mantle is, in general, solid. It turns out that rocks, along with most other solids, flow by a solid-state, creeping motion, especially when they are hot and given enough time.
This is what happens in the mantle. Based on observations of the rates at which the surface of Earth moves, geologists estimate the mantle convectively flows at rates of several centimeters a year. The heat driving mantle convection has three sources.
Mantle convection is the main mechanism by which this heat escapes from the interior of Earth. Plate tectonics refers to the movement of the rigid plates around the surface of Earth. The outer portion of the planet, or lithosphere, is relatively rigid because it is relatively cold.
The lithosphere varies in thickness but is typically a hundred or so kilometers thick. It includes the upper mantle and both the continental and oceanic crust.
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These plates may move away from, move by, or collide with each other. This process forms ocean basins, shifts continents, and pushes up mountains.