What is Tectonics Plate?
Tectonics plates illustrate the characteristics, activities and distribution of oceans and continents on Earth’s surface in past and present.
The tectonic plates also called lithospheric plate is a huge uneven shaped piece of solid slab composed of both continental and oceanic lithosphere. The lithosphere consists of the crust and outer mantle. The lithosphere moves around due to the presence of asthenosphere below the lithosphere.
Tectonics plates: History
Alfred Wegener in 1912, proposed a theory of continental drift in which he was unable to interpret the movement of continents around the planet. Plate tectonics is the new version of continental drift. Plate tectonics can be explained by the geologic features in their region that were unique to that particular region – Van der Elst, seismologist. All geologic features are driven by the relative motion of tectonic plates.
Tectonics plates: Number of plates
There are 9 major plates – North American, Pacific, Eurasian, African, Indo-Australian, Australian, Indian, South American and Antarctic. The largest plate is Pacific plate at 39,768,522 square miles, mostly located under the ocean, moving northwest at speed of around 2.75 inches per year.
Tectonics Plates: Mechanism
- The surface of the Earth covered by a sequence of crustal plates.
- The continuous moving of the oceanic floor is driven by convection in the mantle. Hot material rise starts from the centre, cold mantle sink at the edge, “It’s like a boiling pot on the gas stove”.
- At the mid-ocean ridge, the crustal plates move in different directions due to pushing and spreading of convention current beneath the plates.
- Convention currents are driven by heat produced from radioactivity present in the Earth’s mantle.
- At a subduction zone, the 2 tectonic plates come across one tectonic plate slide beneath the outer back into the mantle.
The Pacific Ocean is surrounded by many volcanoes along subduction zones, like “Ring of Fire”.
Tectonics Plate: Boundaries
- Subduction zone or convergent margins – the crust is destroyed as the 2 plates come close e.g., between an oceanic and continental plate; or between two oceanic plates; and between two continental plates.
- Divergent margins – the new crust is generated as 2 plates spread apart e.g., seafloor-spreading ridges/ continental rift zones – East Asia Rift, Mid-Atlantic Ridge.
- Transform margins – the crust is neither produced nor destroyed as the plates slide horizontally past each other e.g., San Andreas Fault, California.
Tectonics Plate: movement
The mobile rock beneath the rigid plates moves in a circular manner. The heated material rises to the surface, spreads and begins to cool, and then sinks back into deeper depths. This cycle is repeated over and over to generate what we call a convection cell or convective flow. Heat within the earth comes from two main sources: radioactive decay and residual heat. The slow movement of the hot, softened mantle
that lies below the rigid plates is the driving force behind the plate movement.
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