Theinner coreis in the centre and is the hottest part of the Earth. It is solid and made of iron and nickel.
Theouter coreis a liquid layer, also made of iron and nickel.
Themantleis the largest layer. It is made ofsemi-moltenrockcalledmagma. It is hard in the upperparts, but beginning to melt lower down.
Thecrustis the outer layer of solid, thin rock on which we live.
There are two different types of crust:continental crust, which carries land, andoceanic crust, which carries water.
These crusts are broken up into pieces calledplates.
The point where two plates meet is called aplate boundary. This is where earthquakes and volcanoes are most likely to occur.
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Earthquakes
Earthquakes are the vibration of the crust due to movement of tectonic plates.
Thefocusis the point inside the Earth's crust where the pressure is released. Theepicentreis the point above the focus, on the Earth's surface. The most severe damage will happen close to the epicentre.
Thepowerof an earthquake is measured using aseismometerwhich plots vibrations on aseismograph.
The strength of an earthquake is measured on theRichter scalewhich is numbered 0-10. An Earthquake measuring seven or eight can be devastating.
LEDCsoften suffer more from the effects of volcanoes and earthquakes. This is because they have weakercommunicationsystems, lower standard of buildings and less funds for evacuation and eventual aftermath.
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Volcanoes and volcanic eruptions
Volcanic eruptions can happen atdestructiveand constructive boundaries. Volcanoes form whenmagmarises through cracks or weaknesses in the Earth's crust.
Pressure builds and magma explodes to the surface causing a volcaniceruption. The lava from the eruption cools to formnew crust. After several eruptions, the rock builds up to form a volcano.
Themagma chamberis a collection of magmabelowthe volcano.
Themain ventandsecondary ventare where the magma escapes.
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