Restless Earth and Natural hazzards

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  • Created on: 17-02-15 16:31

Restless Earth and Tectonic plates

The Earth’s crust is made up from an inner core, outer core, mantle and crust.

• The crust is divided by lots of slabs called tectonic plates, (floating on the mantle)

.• Plates are made up of two types of crust-Continental crust is thicker and less dense than Oceanic which isthinner and more dense

.• The plates are moving because the rock in the mantle underneath them is moving.

• The places where plates meet are called boundaries, or plate margins

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Plate Margins-Destructive plate margins

Where 2 plates are moving towards each other,e.g. along the east coast of Japan and the Nazca plate sub-ducting under the SouthAmerican plate.

When an oceanic plate (Nazca) and acontinental plate meet, the denser oceanicplate is forced down into the mantle anddestroyed.

This often creates volcanoes and oceantrenches (very deep sections of the ocean floorwhere the oceanic plate goes down).

Constructive Margins: Are where 2 plates are moving away from each other. e.g. at the mid-Atlantic ridge- Iceland. Magma (molten rock) rises from the mantle to fill the gap and cools, creating new crust.

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Conservative plate margins

MarginsThe San Andreas Fault is an example ofconservative margins. The 2 plates aremoving sideways, past each other, or inthe same direction but one movingfaster than the other.

-Crust isn’t created or destroyed. Fold Mountains.

-Fold Mountains are formed on destructive plate margins.

-Rivers carry sedimentary rocks such as sandstone and limestone.

-They are deposited into depressions. The Himalayas in Asia were formed by -After a few million years the 2 continental plates.

-Sediments are compressed into sedimentary rocks then forced upwards into a series of folds by the movement of tectonic plates.

-The Andes in S.America were formed by an oceanic and continental plate.

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Formation of Fold mountains

Fold moutains are formed by crust which has been uplifted and folded by compressional forces. This occurs along convergent plate boundaries where two plates move towards each other, between continental plates or between an oceanic and a continental plate.

The crust and the rocks become bent and crumpled with massive layers of Earth's crust becoming uplifted as a result, forming spectacular fold mountains.

When two continental plates move towards each other, both plates are forced upwards in a series of folds. This caused big problems for early geologists who struggled to explain why they were finding fossils of sea creatures high up in mountains such as the Himalayas. We now know that the fossils got there due to uplift of sedimentary rocks found along the edges of the plates.

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Case Study of a Fold mountains (Alps)

The Alps is a Fold Mountain range, formed around 30 million years ago by the collision of the African and European plates

.• Population: 12 million

• Farming: Slopes have been terraced for vineyards- Lavaux Switzerland and goats are grazed for cheese, meat and milk

• HEP: Switzerland gets 60% of its electricity from HEP stations in the Alps.• Mining: Has declined due to cheaper foreign sources.• Forestry: Scots Pine is planted all over the Alps as it’s more resilient to goats.• Tourism: 100 million tourists per year= huge part of economy. 70% of tourists visit in winter. New villages have been built, e.g. Tignes in France.

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Adaptions to the Alps

1) Steep relief: Goats are farmed because they’re well adapted to steep mountains. Manmade defences are used to protect against avalanches and rock slides

.2) Poor soils: The soil isn’t great for crops, so animals are grazed.

3) Limited communications: Brenner Pass between Austria and Italy has been built but snowoften blocks it up and it takes a while to travel along it. So tunnels have been cut through forfast transport links. For example, the Lotschberg Base Tunnel has been cut through theBernese Alps in Switzerland.

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What happens at the different plate margins?

 

Destructive- move towards, Nazca plate and S.American and on the east coast of Japan.Constructive- move away from each other, Eurasian and North American (over Iceland-mid Atlanticridge).

Conservative- side by side, San Andreas FaultWhere do fold mountains occur and what are they?They occur at destructive plate margins when they collide and fold the sediments upwards.5 Human uses of fold mountains and an example of one?Mining, forestry, tourism, HEP,Farming.

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Formations of Volcano

Volcanoes• Are found at destructive AND constructive plate margins.

• At destructive plate margins:The denser oceanic plate sub-ducts under the continental plate- creating an ocean trench.Where the oceanic plate is destroyed in the mantle the magma rises through cracks in thecrust called vents.The magma erupts onto the surface (now called lava) forming a volcano.

• At constructive plate margins:The magma rises up into the gap created by the plates moving apart, forming a volcano.Some volcanoes also form over parts of the mantle that are really hot (hotspots) e.g. in Hawaii.

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Types of volcano

Types of volcano:•

Composite: Made up of layers of ash and lava that have cooled and hardened into layers.• The lava is usually thick and flows slowly. It hardens to form a steep sided volcano.• Example: Mount Fuji, Japan

• Shield: Made up of only lava = lava layers. Lava is runny, flows quickly and spreads over a large area. This forms a low, flat volcano• Example: Mauna Loa, Hawaii

• Dome: Made up of only lava, the lava Scientists try and predict volcanic eruptions is thick, flows slowly and hardens by monitoring escaping gas, tiny quickly, forming a steep sided volcano earthquakes and changes in shape and size • Example: Mount Pelée, Caribbean of the volcano.

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Case study Monserrat-Causes

The Soufriere Hills in Montserrat erupted on June 25th 1997.• 19 killed• Montserrat is above a destructive plate margin, where the Atlantic Plate is being forced under the Caribbean plate.

• Magma rose, forming an underground pool of magma.The rock above the pool collapsed, opening a vent and causing the eruption.

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Case study Monserrat Primary impacts

1) Large areas were covered in volcanic material- the capital city, Plymouth was buried under 12m of mud and ash.

2) Over 20 villages and two thirds of homes on the island were destroyed by pyroclastic flows (fast moving clouds of super heated gas and ash).

3) Schools, hospitals, the airport and the port were destroyed.

4) Vegetation and farmland were destroyed.5) 19 people died and 17 were injured. .

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Case Study Monserrat Secondary impacts

 1) Fires destroyed many buildings including local government offices, the police headquarters and the town’s central petrol station.

2) Tourists stayed away and businesses were destroyed disrupting the economy.

3) Population decline- 8000 of the island’s inhabitants have left since the eruptions began in 1995.

4) Volcanic ash from the eruption has improved soil fertility.

5) Tourism on the island is now increasing as people come to see the volcano.

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Case study Monserrat Immediate responses

1) People were evacuated from the south to safe areas in the north.

2) Shelters were built to house evacuees.

3) Temporary infrastructure was also built, e.g. roads and electricity supplies.

4) The UK provided £17 million of emergency aid (Montserrat’s an overseas territory of the UK).

5) Local emergency services provided support units to search for and rescue survivors

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Case studys Monserrat Long term responses

1) A risk map was created and an exclusion zone is in place. The south of the island is off limits while the volcano is still active.

2) The UK has provided £41 million to develop the north of the island – new dock, an airport and houses have been built in the north.

3) The Montserrat Volcano Observatory has been setup to try and predict further eruptions

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Supervolcano

 Are massive volcanoes- only at destructive margins. E.g. Yellowstone National Park- USA.Formation

1) Magma rises up through cracks in the crust to form a large magma basin below the surface.The pressure of the magma causes a circular bulge on the surface several kms wide.

2) The bulge eventually cracks, creating vents for lava to escape through. The lava erupts out ofthe vents causing earthquakes and sending up gigantic plumes of ash and rock.

3) As the magma basin empties, the bulge is no longer supported so it collapses- spewing upmore lava.

4) When the eruption’s finished there’s a big crater (called a caldera) left where the bulgecollapsed. Sometimes these get filled with water to form a large lake, e.g. Lake Toba in Indonesia.

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Charecteristics of a Supervolcano

Characteristics of a supervolcano:

Flat (unlike normal ones which are mountains).

-Cover a large area

-Have a caldera (normal volcanoes just have a crater atthe top).

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Concequences of Supervolcano eruptions

Thousands of cubic kms of ash, rock and lava will be thrown out with the eruption.

 A thick cloud of super heated gas and ash will flow at high speed from the volcano, killing, burning and burying everything it touches.

 Everything within 10 miles is destroyed.

 Ash shot high into the air will block out sunlight over whole continents.

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How do scientist monitor Volcanos

By monitoring escaping gas, changes in size of the volcano and tiny earthquakes.

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Earthquakes

Occur at all 3 types of plate margins.• Are caused by tension that builds up.

Destructive margins:Tension builds up when one plate gets stuck as it’smoving down past the other into the mantle.

Constructive margins:Tension builds along cracks within the plates as theymove away from each other.Conservative margins:Tension builds up when plates that are grinding past eachother get stuck.

 The plates eventually jerk past each other sending out shockwaves(vibrations) = earthquake.

The waves spread out from the focus (the point in the Earth where theEarthquake starts).The nearer the focus the waves are the more destructive and strongerthey are.The epicentre is the point on the Earth’s surface straight above thefocus.Earthquakes can be measuredThe Richer Scale: measures the amount of energy released.

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LEDC Haiti earthquake case study Causes

LEDC Haiti

Causes

The earthquake was caused by the North American Plate sliding past the Caribbean Plate at a conservative plate margin. 

Both plates move in the same direction, but one moves faster than the other. 

The pressure that was built up because of the friction between the 2 plates was eventually released causing a magnitude 7 earthquake on the Richter Scale with an epicentre 16 miles West of Port-au-Prince and a shallow focus of 5 miles. 

The earthquake struck at 16:53 (4:53pm) local time on Tuesday 12 January 2010

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LEDC Haiti Earthquake case study Effects Primary

316,000 people were killed and 1 million people were made homeless. 

3 million people were affected by the earthquake

250,000 homes and 30,000 other buildings, including the President’s Palace and 60% of government buildings, were either destroyed or badly damaged

Transport and communication links were also badly damaged by the earthquake

Hospitals (50+) and schools (1,300+) were badly damaged, as was the airport’s control tower.

The main prison was destroyed and 4,000 inmates escaped

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LEDC Haiti Earthquake case study secondry effects

1 in 5 people lost their jobs because so many buildings were destroyed.  Haiti’s largest industry, clothing was one of the worst affected

The large number of deaths meant that hospitals and morgues became full and bodies then had to be piled up on the streets

The large number of bodies meant that diseases, especially cholera, became a serious problem.

It was difficult getting aid into the area because of issues at the airport and generally poor management of the situation.

People were squashed into small shanty towns due to their homes being destroyed but this caused diseases to spread quicker.

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LEDC Haiti Earthquake Statistics

Development Indicator

Value

GDP per capita (average income) $1,200 per person each year People living in poverty 80% of people live on $2 or less per day Life expectancy 62 years old People per doctor 0.25 doctors per 1,000 people Adult literacy rate 53% over 15 years old can read/write Access to clean water 46% of people have access to clean water

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LEDC Haiti Earthquake responses

Short Term

Long Term

$100 million in aid given by the USA and $330 million by the European Union 98% of the rubble on the roads hadn’t been cleared restricting aid access 810,000 people placed in aid camps 1 million people still without houses after 1 year so still have to live in aid camps 115,000 tents and 1,000,000+ tarpaulin shelters provided Support for people without jobs, which equates to nearly 70% of the population, through cash/food-for-work projects Healthcare supplies provided to limit disease Temporary schools created and new teachers trainee Lack of immediate aid through poor planning, management and access meant that people had to try and rescue each other Water and sanitation eventually supplied for 1.7 million people 4.3 million people provided with food rations in the weeks following the earthquake

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MEDC Newzealand Earthquake Causes

The 6.3 magnitude earthquake struck New Zealand at 12:51 on 22 February 2011.  The epicentre was 6 miles South East of Christchurch and the focus was very shallow at 3.1 miles.  The earthquake occurred on a conservative plate margin where the Pacific Plate slid past the Australian Plate in the opposite direction.  It was technically an aftershock from a larger earthquake in 2010 but the impacts were more severe.

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MEDC New Zealand Earthquake Case study Effects

Primary

Secondary

181 people were killed and around 2,000 people were injured Business were put out of action for long periods causing losses of income and jobs Hundreds of kilometres of water and sewage pipes were damaged Schools had to share classrooms because of the damage to other school buildings 50% + of Central City buildings severely damaged including the city’s cathedral which lost its spire Damage to roads through liquefaction made it difficult for people and emergency services to move around Liquefaction (where the ground gets saturated and loses strength) caused lots of damage to roads and buildings People were affected mentally by the earthquakes and needed support Part (size of 20 football fields) of the country’s longest glacier was broken off creating a large iceberg Christchurch could no longer host Rugby World Cup matches so lost the benefits, e.g. tourism and income, they would bring 80% of the city was without electricity

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MEDC Earthquake New Zealand Responses

Short Term

Long Term

Cared for the most vulnerable people and ensured people were safe from dangerous buildings Paid $898 million in building claims Chemical toilets were provided for 30,000 residents Provided temporary housing and ensured all damaged housing was kept water tight Areas were zoned (green, orange, white, red) to classify damage/cost of repairs Water and sewerage was restored for all residents by August International aid was provided in the form of money (around $6-7 million) and aid workers Roads and houses were cleared of silt from liquefaction by August and 80% of roads/50% of footpaths were repaired

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MEDC New Zealand statistics

GDP per capita (average income) $27,700 per person each year People living in poverty N/A Life expectancy 81 years old People per doctor 2.4 doctors per 1,000 people Adult literacy rate 99% over 15 years old can read/write Access to clean water 100% of people have access to clean water

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Tsunami case study boxing day 2004

What is a Tsunami?

A tsunami is a series of continuous waves caused when huge amounts of water get displaced.

CASE STUDY

Causes

West Coast of Indonesia/ Indian Ocean26th December 2004 9.1 Richter Scale Waves 30m high Indonesia, India, Thailand and Sri Lanka were the worst affected.There was NO EARLY WARNING SYSTEM.

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Tsunami case study Boxing day 2004

230,000 people were killed

Whole towns and villages were destroyed

1.7 million lost their homes

Infrastructure (roads, waterpipes electricity lines) were severely damaged-

5-6 million people needed emergency food, water and medical supplies-

Economic damage: fisherman lost livelihoods and tourism plummeted because of total destruction and the fear of the event reoccuring,

Environmental damage: salt from sea all over plants prevented growth.

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Tsunami Boxing day 2004 short term responses

1) Hundreds of millions of pounds had been pledged by foreign govs, charities to give survivors food, water, shelter, medical attention.

2) Foreign countries sent ships, planes and soldiers to help rescue people, distribute food and help clear up the distruction left by the tsunami.

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Tsunami Long term responses Boxing day 2004

1) Billions of pounds pledged to help re-build

2) Programmes set up to help people get back to work

3) A tsunami warning system has been put in place in the Indian Ocean

4) Disaster Management Plans have been put in place in some countries

5) Volunteers have been trained for future tsunamis

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