- The inner core is in the centre and is the hottest part of the Earth. It is solid and made of iron and nickel.
- The outer core is a liquid layer, also made of iron and nickel.
- The mantle is the largest layer. It is made of semi-molten rock called magma. It is hard in the upper parts, but beginning to melt lower down.
- The crust is the outer layer of solid, thin rock on which we live.
- There are two different types of crust: continental crust, which carries land, and oceanic crust, which carries water.
- These crusts are broken up into pieces called plates.
- The point where two plates meet is called a plate boundary. This is where earthquakes and volcanoes are most likely to occur.
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- Earthquakes are the vibration of the crust due to movement of tectonic plates.
- The focus is the point inside the Earth's crust where the pressure is released. The epicentre is the point above the focus, on the Earth's surface. The most severe damage will happen close to the epicentre.
- The power of an earthquake is measured using a seismometer which plots vibrations on a seismograph.
- The strength of an earthquake is measured on the Richter scale which is numbered 0-10. An Earthquake measuring seven or eight can be devastating.
- LEDCs often suffer more from the effects of volcanoes and earthquakes. This is because they have weakercommunication systems, lower standard of buildings and less funds for evacuation and eventual aftermath.
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Volcanoes and volcanic eruptions
- Volcanic eruptions can happen at destructive and constructive boundaries. Volcanoes form when magma rises through cracks or weaknesses in the Earth's crust.
- Pressure builds and magma explodes to the surface causing a volcanic eruption. The lava from the eruption cools to form new crust. After several eruptions, the rock builds up to form a volcano.
- The magma chamber is a collection of magma below the volcano.
- The main vent and secondary vent are where the magma escapes.
- Active volcanoes erupt frequently.
- Dormant volcanoes are temporarily inactive.
- Extinct volcanoes are never likely to erupt again.
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