Restless Earth

Restless Earth topic

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The Earth's make up

The Earth is made up of a Core, Mantle and Crust. The crust is made up of 4 parts, the:
Atmosphere - the layer of gases which make up the air around us, it is needed for oxygen for us to breathe, CO2 for plant growth, weather and climate and the greenhouse effect which keeps the planet warm.

Hydrosphere - the layer of water - seas, groundwater, rivers, lakes and ice on the Earth's surface. The water is used for plants and animals and the water cycle which moves water around the planet.

Biosphere - The very thin layer of living things living on the crust, plants and animals on the Biosphere provide us with food and the many living things can be useful for making medicine and for fuel.

Geosphere -  The rocks of the Earth's crust and deeper into the Earth's core. The Earth's core makes a magnetic field protecting us from space radiation. We also use the rocks, minerals and fossil fuels for many different resources.

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Tectonic Plates

The Earth's crust is split into Tectonic Plates, there are two types of Tectonic plate:

Continental - Mostly granite which is a low density igneous rock, continental crust is on average about 30-50km thick.

Oceanic - Denser than continental plates but much thinner, oceanic crust is on average only about 6-8km thick. It is made of an igneous rock called Basalt.

The plates move around the earth due to convection currents in the Mantle 'powered' by the radioactive decay of elements such as Thorium and Uranium. We know that the plates have moved over time because of evidence such as identical rocks and fossils found in different continents which suggest that the continents were at once point all joint together as a Super continent known as Pangea. Where the plates interact is called a plate boundary, when the plates do interact, natural disasters such as volcano eruptions and earthquakes occur.

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Volcanoes and Earthquakes

Volcanoes and Earthquakes occur on plate boundaries with the exception of places such as Hawaii which occur on Hot Spots. A Hot Spot is a fixed spot on the mantle where magma rises to the surface in the form of Plumes.

There are two types of volcano:

Composite - gives off Andesitic Lava - low temperature, high silica, lots of dissolved gas, the magma is more likely to explode when it reaches the surface of the Volcano.
Shield - gives off Basaltic Lava - high temperature, low in silica, low gas content, flows long distances on the Earth's surface and creates very large, gently sloping shapes.

Earthquakes can be measured using the:
Richter Scale - a scale that measures the magnitude of an Earthquake on a scale of 1-10.
Mercalli Scale - a scale that looks at the damage done by the Earthquake. 

Volcanoes are measured using seismometers or seismographs. 

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Predicting Earthquakes are almost impossible as they usually occur suddenly. However, Volcanoes can be predicted by:
Air crafts measuring the amount of gas given off by the volcano
Tilt meters detecting when the volcano swells up as it fills with magma
Seismometers monitoring Earth Tremors
Boreholes which are used to measure water temperature as the magma heats up. 

To reduce the damage caused by volcanoes and earthquakes, preparation is useful, this can be done in a number of ways including:
Emergency Plans
Warning Systems
Aseismic buildings
Community Prep
Observing animal behaviour
Evacuation plans
Short term hazard responses such as tents, blankets and food
Long term hazard responses to improve preparedness of people and reduce the impact of future events.

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Montserrat Eruption, 1995 (Composite Volcano)

Montserrat lies on a destructive plate boundary in the Carribean.

Primary effects:
Two-thirds of the island was covered in ash,
50% of the population were evacuated to the North to live in makeshift shelters,
23 people died in 1997,
The capital city Plymouth became a ghost town,
Valleys were blocked with ash causing floods,
The airport and port were closed,
Farmland, schools and hospitals were destroyed,
Forest fires caused pyroclastic flows.
Secondary effects:
Remaining inhabitants have had to endure harsh living conditions in North,
Port and airport remain closed so transport is a problem,
Tourist industry is still suffering,
Half the population have left and not returned to the island.
£41 million given in Aid by the British Government
Money given to individuals to help them move to other countries
Riots occurred due to local complaints of the British not doing enough to help the island
MVO set up to study the volcano along with a risk assessment to help Islanders understand risky areas. 

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Icelandic Eruption, 2010 (Shield Volcano)

Iceland lies on a constructive plate boundary where the Eurasian and North American plate are moving apart.
Primary effects:
Opening of a ground fissure of 150m
Rise in water levels and temperatures in rivers
Contamination of water sources and rivers due to ash
Ash cloud reached Europe within 2 days disrupting flights
Eruption cloud reached 8km high
Secondary effects:
Long-term impacts on farming due to the thick layer of ash that has fallen on farms and pastures and has become wet and compact, making it difficult to continue,
Increase in short-term volcano tourists,
Global disruption of flights leading to increase in insurance claims and profit declines for airline companies,
Possible chain reaction leading to other eruptions in the area,
Shorter and colder summer is Europe.
800 farming families evacuated from the local area,
Flights to and from Iceland postponed. 

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Kashmir Earthquake, 2005 (LEDC)

Kashmir is a mountainous region between Pakistan and India located on a Collision plate boundary involving the Eurasian and Indian Plates. The earthquake measured a 7.6 on the Richter scale.

Primary effects:
Pakistan suffered around 73,000 deaths - many children as it was a school day,
Many more died as it was Ramadan and they were sleeping,
2.8 million people left homeless,
Property cost of $440 million.
Secondary effects:
Lack of food, clean water and shelter left 120,000 people at risk of death,
Secondary landslides expected,
Winter snows were due to start which would make the relief effort very difficult.
International aid agencies used helicopters to fly in blankets, tents, basic provisions and medical supplies to the area. 

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Loma Prieta Earthquake, 1989 (MEDC)

Located on a Conservative plate boundary involving the Pacific plate slipping past the North American plate in California. This earthquake measures at 6.9 on the Richter Scale.

Primary Effects:
63 people died,
3, 757 injured,
12,000 left homeless,
Property cost of $10 billion.
Secondary Effects:
Increased number of home insurance claims,
Decline in tourism as the area doesn't feel the same,
Collapse of overpasses meaning that accessibility is difficult for the emergency services. 

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