A plate is a rigid lithospheric slab in the earth surface. If two tectonic plates collide, they form a convergent plate boundary. Usually, one of the converging plates will move beneath the other, which is known as subduction. Deep trenches are often formed where tectonic plates are being subducted and earthquakes are common.
- Plate tectonics theory deals with the dynamics of Earth’s outer shell known as the lithosphere that provides an understanding for mountain-building processes, volcanoes, and earthquakes as well as the evolution of Earth’s surface and reconstructing its past continents and oceans.
- According to the theory, the lithosphere, is about 100 km (60 miles) thick and overlies a plastic (moldable, partially molten) layer called the asthenosphere. The lithosphere is broken up into several plates which move relative to each other.
- A tectonic plate is also called lithospheric plate, the theory of plate tectonics proposed that “the earth’s lithosphere is divided into seven major and some minor plates, young folded mountain ridges, trenches, and faults surround these major plates.
- Convection currents beneath the plates move the crustal plates in different directions. The source of heat driving the convection currents is radioactivity deep in the Earth’s mantle. They are believed to cause Paleomagnetism in the earth surface around the poles.
- In Convergent plate boundary, two lithospheric plates collide against each other and the zone of collision may undergo crumpling and folding and folded mountains may emerge. This is an orogenic collision.
- Himalayan Boundary Fault is one such example. When one of the plates is an oceanic plate, it gets embedded in the softer asthenosphere of the continental plate and as a result, trenches are formed at the zone of subduction. The subducted material gets heated, up and is thrown out forming volcanic islands and dynamic equilibrium is achieved.
- Divergent plate Boundary: As the name itself suggests, in this kind of interaction, the plates diverge [move away from each other].
- Mid-oceanic ridges are formed due to this kind of interaction. Here, the basaltic magma erupts and moves apart (sea floor spreading).
- On continents, East African Rift Valley is the most important geomorphological feature formed due to divergence of African and Somali plates.
- Such edges are sites of earth crust formation (hence constructive) and volcanic earth forms are common along such edges.
- Transform plate boundary: It is formed when two plates move past each other. In this kind of interaction, two plates grind against each other and there is no creation or destruction of landform but only deformation of the existing landform. [Crust is neither produced nor destroyed as the plates slide horizontally past each other].
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