In addition, the diving plate melts and is often spewed out in volcanic eruptions such as those that formed some of the mountains in the Andes of South America.Īt ocean-ocean convergences, one plate usually dives beneath the other, forming deep trenches like the Mariana Trench in the North Pacific Ocean, the deepest point on Earth. As the overlying plate lifts up, it also forms mountain ranges. These convergent boundaries also occur where a plate of ocean dives, in a process called subduction, under a landmass. Mount Everest, the highest point on Earth, may be a tiny bit taller tomorrow than it is today. As the mash-up continues, the mountains get higher. India and Asia crashed about 55 million years ago, slowly giving rise to the Himalaya, the highest mountain system on Earth. Where plates serving landmasses collide, the crust crumples and buckles into mountain ranges. They move at a rate of one to two inches (three to five centimeters) per year. The movement of the plates creates three types of tectonic boundaries: convergent, where plates move into one another divergent, where plates move apart and transform, where plates move sideways in relation to each other. Most geologic activity stems from the interplay where the plates meet or divide. (This includes the crust and uppermost part of the mantle.) Churning currents in the molten rocks below propel them along like a jumble of conveyor belts in disrepair. The plates make up Earth's outer shell, called the lithosphere. The tiny Juan de Fuca plate is largely responsible for the volcanoes that dot the Pacific Northwest of the United States. Though smaller in size, the minors are no less important when it comes to shaping the Earth. Six of the majors are named for the continents embedded within them, such as the North American, African, and Antarctic plates. The rubbing caused by the sliding is what causes earthquakes along the transform faults one example would be the San Andreas fault.There are a few handfuls of major plates and dozens of smaller, or minor, plates. Unlike the other two types of plate boundaries in which new seafloor is created at divergent boundaries and where old seafloor is subducted at convergent boundaries, transform plate boundaries neither create nor destroy the seafloor. The last type of plate boundary is the transform boundary, which is where two plates slide past one another. An example of a subduction zone formed from a convergent boundary is the Chile-Peru trench. Old, dense crust tends to be subducted back into the earth. Subduction zones are the reason why oceanic crust older than 200 million years old cannot be found. This melting leads to heat being transferred upwards and uplifting the crust, eventually developing into a volcano. Whenever a subduction zone is formed, the subducted plate will end up being partially melted by the earth’s internal magma and molten. Convergent boundaries are commonly associated with larger earthquakes and higher volcanic activity. When an oceanic plate converges with a continental plate, the oceanic crust will always subduct under the continental crust this is because oceanic crust is naturally denser. When two oceanic plates converge, the denser plate will end up sinking below the less dense plate, leading to the formation of an oceanic subduction zone. Neither continental crust will subduct underneath one another because of their similar densities. When two continental crusted plates converge, they eventually collide and end up producing mountains this was how the Himalayan Mountains were created. As previously mentioned, depending on what type of crust each converging plate is, different geographic features are formed. When two plates move towards each other, the boundary is known as a convergent boundary. Divergent plate boundaries are commonly associated with shallow earthquakes. On the other hand, if two oceanic plates diverged, a mid ocean ridge would form, which is also known as a spreading center. For example, when two continental plates diverge from each other, an ocean basin is created due to the separation of land. Depending on what type of lithospheric crust each diverging plate is, whether oceanic or continental, varying geographic features are formed. An example of a divergent plate boundary is the Mid-Atlantic Ridge. Spreading centers and areas where new ocean floor are generally located at divergent plate boundaries. ![]() ![]() In the case of divergent plate boundaries, two of earth’s plates move away from each other. There are essentially three types of plate boundaries, which are divergent, convergent, and transform. \)Ĭategorization of plate boundaries is based off of how two plates move relative to each other.
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