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Subduction zones occur when two tectonic plates collide, creating geological formations such as mountain ranges, ocean trenches, and island arcs. They recycle rock by melting it into magma, forming new crust in other zones. Earthquakes and volcanoes are common in these zones, and the Pacific Ring of Fire experiences many tremors. Two continental plates can also converge, forming interior mountain ranges. The surface of the earth never grows or shrinks, as the leading edge of the plate melts into the asthenosphere, while the trailing edge forms from cooling rock.
A subduction zone is a convergent boundary where two tectonic plates collide. Plates are large, dense masses in the earth’s crust, the lithosphere, that float on liquefied rock in the asthenosphere. They are constantly shifting and moving, so when they take the lead, one pushes under the other. These zones create geological formations such as mountain ranges, ocean trenches and island arcs, as well as phenomena such as earthquakes and volcanoes.
Tectonic plates are classified as either oceanic plates that have large bodies of water above them or continental plates that support the land. Geologists learned how subduction works by studying earthquakes in seismology and volcanoes in volcanology. They know that younger pots are less dense than older pots. Generally, oceanic crust is thinner and denser than continental crust. Subduction zones not only make some changes to the landscape, but they recycle rock by melting it into magma so that crust can form in other tectonic zones.
When two oceanic plates meet, a deep underwater trench forms where the thicker plate plunges under the thinner one. At first, a large pressure on the thrust plates causes earthquakes. These open spaces for hot, molten magma so it can seep into underwater volcanoes. Eventually, the material builds up in a ridge until it breaks the ocean’s surface, forming “arcs” of islands and archipelagos. This is how the Philippine Islands came into being.
An oceanic and continental plate meet under different circumstances. Below the coast, their convergence causes the oceanic plate to fall under the continental one, perforating the hot athenosphere. Again, the first stage builds pressure and releases the earthquakes, which is why the Pacific Ring of Fire experiences so many tremors. So, over time, mountains form on land as the continental plate buckles. The Andes are one such mountain range.
Two continental plates can also converge, but this may not technically form a subduction zone. The Earth’s crust does not have sufficiently different densities or thicknesses to be subducted. However, it swells and forms interior mountain ranges without volcanoes, such as the Himalayas.
Along with the divergent zones, the convergent zones ensure that the surface of the earth never grows or shrinks. While the leading edge of the lithospheric plate is eaten away as it melts into the hot athenosphere, the trailing edge forms from the cooling rock. Sometimes, the smaller plates can disappear altogether, eaten up by the magma.
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