Restless Earth

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Unstable Earth	Plates: The large pieces of the Earth's crust. Plate Margins: Where the different plates meet. Two different types of crust- Oceanic and Continental
Oceanic Crust: 5-10 km thick, dense, sinks into the mantle when oceanic and continental crust meets, forms constantly at constructive plate margins, destroyed at destructive plate margins.	Continental Crust: 25-100km thick, less dense, doesn't sink, very old, new crust isn't formed, cannot be destroyed.
Plate Boundaries: the border between two plates is called a boundary. All the tectonic plates are constantly moving in different directions.	Constructive (divergent): where the plates are moving apart. Conservative (transform): where the plates slide past each other. Destructive (convergent): where the plates collide - collision zone.
Plate Margins	Collision Boundary: Two continental plates crash into each other. As they collide they trigger earthquakes. The rocks between the plates gets pushed up and folded.
Constructive Boundary: Two plates move apart from each other. A gap appears and molten magma rises to fill the gap. This solidifies to create new rocks on the sea bed. Over time the layers of rock build up.	Conservative Boundary: Two plates are sliding in the same direction. However the pacific plate is moving faster. As the plates slide past, they snag. Pressure and tension build up as the rocks lock together. Eventually they break causing a surge forward- earthquakes.
Destructive Boundary: Plates are pushed together and the oceanic crust gets subducted beneath the continental crust. Oceanic plate sticks and locks as it is trying to move from under the Cont plate. Heat from friction and the mantle start to melt the subducted plate.	Subduction: the transformation into magma of a denser tectonic plate as it dives under a less dense plate.
Landforms at Plate Margins	Fold Mountains lie on a collision zone (destructive plate margin). Ocean Trenches are also found at destructive plate margins.
Composite Volcanoes- found at destructive plate margins. Have steep sides. Made up of alternate layers of ash and lava. Eruptions can be violent- expelling steam, ash, lava and rock- but they don't happen often.	Shield Volcanoes- found at constructive plate margins. Have a wide base and gently sloping sides. Lava is runny and flows a long way. There can be frequent eruptions but they are not violent.
Montserrat- LEDC	British overseas territory, located in the Caribbean. Part of the volcanic arc which is formed at a destructive plate margin. The island is dominated by Soufriere Hills (volcanic)- takes up 80%. Fertile soil because of the volcanoes.
Why?- millions of years the atlantic plate had been pushed under the Caribbean plate. Magma formed and pushed it's way through the ocean floor, creating underwater volcanoes which turned into islands (Lesser Antilles arc). Plates moving-subduction happening.	This caused Montserrat's volcano to wake again. August 1995- Soufriere hills awaken. June 1997- the big one killing 19 people. Pyroclastic flow.
Effects- More than half became uninhabitable. Infrastructure was destroyed. 19 died, many fled. Farms, homes and the capital were destroyed/abandoned. Tourism stopped. Economy was destroyed. Long-term health effects because the ash contained quartz which caused Silicosis.	Immediate responses- August 1995, many residents evacuated to north of the island. Many left the island completely. November 1997 pop fallen from 12,000 to 3500. British government spent millions on aid. Charities set up temp schools.
Long-term responses- some returned, 2010 pop risen to 5000. Pop structure changed, many young people left and didn't return. British government spent £200million helping to restore electricity and water, build a new harbour , new airport and roads.	Monitoring and predicting volcanic eruptions- Montserrat Volcano Observatory was set up in 1996. Almost everything a scientist can think of has been used to monitor the volcano.
Montserrat's future- In 2005 tourists started to visit again. Little Bay is being developed as the new capital. It is hoped that Little Bay will stimulate economic growth	Key words: Pyroclastic, primary and secondary responses.
Supervolcanoes- Yellowstone National Park (USA)	Supervolcano implies an eruption of magnitude 8 on the Volcano Explosivity Index. Meaning that more than 1,000 cubic kilometres of magma (partially molten rock) are erupted.
Geology - The park is home to one of the world's largest calderas with over 10,000 thermal features and more than 300 geysers.	See Mr M
Earthquake	An earthquake is the shaking of the Earth's crust, caused by sudden rock movement.
Earthquakes tend to occur in long belts. The biggest one goes around the whole Pacific Ocean. Another one runs down the middle of the Atlantic Ocean. These belts follow the plate margins.	Earthquakes occur at plate margins because of friction- the plates try to move and get stuck.. Pressure builds as plates try to move. If pressure is released slowly then we hardly feel movement.
If pressure is released suddenly, it can send out huge pulses of energy- causing the Earth's surface to move violently. Earthquakes occur at all four types of plate margins.	They occur at: Destructive margins, where one plate tries to sink below the other. Collision zones, where the plates are pushing together. Constructive margins, when both plates try to move over the mantle. Conservative margins, when plates moving alongside each other get stuck..
Features of earthquakes- when an earthquakes strikes, the ground shakes violently.	...
2004 Boxing Day Tsunami	A tsunami is a series of large waves that form when an earthquake occurs along a fault below the seabed. As the waves approach shallow water they slow down but increase in height. The Boxing Day Tsunami killed nearly 300000.
It hit several countries surrounding the Indian Ocean, with Indonesia being the worst affected.	Immediate responses include foreign aid in the form of essential supplies and money. Longer-term responses included the setting up of an early warning system.
Mangrove Swamps act as a natural barrier, so these are being restored, having been cleared in many areas to make way for building of hotels.	Countries affected: 1. Indonesia, 2. Sri Lanka, 3. India, 4. Thailand, 5. Somalia, 6. Burma, 7. Maldives, 8. Malaysia, 9. Tanzania, 10, Seychelles, 11. Bangladesh, 12. Kenya.

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	Erstellt von Sadhbh Neville vor etwa 9 Jahre