BBC - GCSE Bitesize: Volcanoes and earthquakes
Why do volcanoes occur along constructive and destructive plate boundaries? Are earthquakes and volcanoes only found along tectonic plate boundaries? Views . Then the two aqueducts meet and then go deep into the Earth below. Learn and revise about plate tectonics focusing on the Earth's structure, plate These plates are constantly moving, and volcanoes and earthquakes are found at plate This occurs when oceanic and continental plates move together. Our team of exam survivors will get you started and keep you going. Meet them here. Where tectonic plates meet, the Earth's crust becomes unstable as the plates slide Earthquakes and volcanic eruptions happen at the boundaries between plates. Volcanoes can be very destructive, but some people choose to live near .
The denser plate is subducted underneath the less dense plate. The plate being forced under is eventually melted and destroyed. Where oceanic crust meets ocean crust Island arcs and oceanic trenches occur when both of the plates are made of oceanic crust.
Zones of active seafloor spreading can also occur behind the island arc, known as back-arc basins.
These are often associated with submarine volcanoes. Where oceanic crust meets continental crust The denser oceanic plate is subducted, often forming a mountain range on the continent. The Andes is an example of this type of collision.
- Tectonic Plates and Plate Boundaries
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- Volcanoes and earthquakes
Where continental crust meets continental crust Both continental crusts are too light to subduct so a continent-continent collision occurs, creating especially large mountain ranges. The most spectacular example of this is the Himalayas. Divergent boundaries — where two plates are moving apart. The space created can also fill with new crustal material sourced from molten magma that forms below.
Divergent boundaries can form within continents but will eventually open up and become ocean basins.
Plate Tectonic, Volcanoes and Earthquakes
Along Plate Edges Most earthquakes occur along the edge of the oceanic and continental plates. The earth's crust the outer layer of the planet is made up of several pieces, called plates.
The plates under the oceans are called oceanic plates and the rest are continental plates. The plates are moved around by the motion of a deeper part of the earth the mantle that lies underneath the crust.
These plates are always bumping into each other, pulling away from each other, or past each other. The plates usually move at about the same speed that your fingernails grow.
Earthquakes usually occur where two plates are running into each other or sliding past each other. Figure 1 - An image of the world's plates and their boundaries. Notice that many plate boundaries do not coincide with coastlines.
Along Faults Earthquakes can also occur far from the edges of plates, along faults. Faults are cracks in the earth where sections of a plate or two plates are moving in different directions. Faults are caused by all that bumping and sliding the plates do. They are more common near the edges of the plates. Types of Faults Normal faults are the cracks where one block of rock is sliding downward and away from another block of rock.
These faults usually occur in areas where a plate is very slowly splitting apart or where two plates are pulling away from each other.
A normal fault is defined by the hanging wall moving down relative to the footwall, which is moving up. Figure 2 - A normal fault.