Living in an active zone

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  • Created by: chloe
  • Created on: 22-05-13 17:17

Plate tectonics

Used to be a supercontinent - pangea.All the plates were joined together.

The plates have drifted apart.

Why do plates move?  -

Heat from the core of the earth causes magma to rise towards the surface. Slighlty cooler magma falls to replace it creating convection currents in the mantle. The currents causes friction on the underside of the plates. The dragging effect under the plates causes them to move. This is known as continental drift.

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Types of Volcano

Dormant - not errupted recently but likely to errupt again.

Active - is errupting at the moment, has errupted recently.

Extinct - not going to errupt again.

Shield volcano - wide base, runny flowing lava - spreads easily

Strato volcano - made up of layers, sticky lava.

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Plate margins

Constructive plate margin - plates move apart. Volcano forms as magma flows up through crust. Magma cools and forms new land - igneous rock.

Example - Iceland is on a constructive plate margin - between North American and Eurasian plates. Iceland is expanding because new land is formed. There are steep escarpments either side of a rift valley. Water is closer to core so gets heated naturally creating a geothermal spring.

Destructive plate margins - plates move together. Oceanic plate subducts under continental plate in subduction zone and land melts into magma - land is destroyed. Land buckles up and forms fold mountains. Oceanic trench formed where plates collide.

Example - Andes mountain range, south America - on a destructive plate margin - fold mountains.

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Primary and secondary hazards

Primary hazard - direct result of hazard

Pyroclastic flow- burning clouds of ash and gas.

Tephra - rock from volcanoes

Lahars - ash and gas in a cloud mixed with water to make a flowing cement.

Ash falling on buildings etc.

Secondary hazards - occur because of a change because of hazard

fires

Transport difficulties - railways and roads destroyed

rubble (quakelakes after earthquakes)

Tsunamis

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Earthquakes

occur when plates move passed each other and get stuck, when they move they cause movement.

Where the plates hit each other is the focus, the epicente is the place directly above where the earthquake is strongest.

Earthquakes measured on richter scale

Sichuan Earthquake may 2008

7.9 on richter scale

87,000 people died

rescues were difficult because of aftershocks

secondary hazards created - quakelakes - flooding

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why do people live near volcanoes

Geothermal energy - water heated by heat from the earth

volcanic ash fertilises soils - good for farming

companies dig rock - pumice

Toursit attration - B&B's set up there

For the scenery

Negatives

houses get covered in ash

gases can damage the atmosphere in surrounding area - make it hard to breathe

Erruptions cause problems

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Monitoring Volcanoes

Montserrat volcano observatory - sulfur hills

seismographs pick up tremors

GPS detects deformed land

tiltmetres record movements

gas readings monitor sulfur dioxide levels

video cameras monitor appearance

Hazard mapping - dividing the land into areas safe to live, and areas too dangerous for humans

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Coping with natural hazards

Short term -

LEDC's (less economically developed countires) are poor and reactive.

evacuate people, search for survivors, temporary camps for survivors, medical supplies

MEDC's (more economically developed countries) are rich and pre-emptive

Spray water from planes to cool lava

earth barriers to channel lava flow

aerial bombing to dissipate the flow

Long term-

LEDC's - basic warning systems

MEDC's

training peple to cope with disatser, educating people from early ages (california -shake it out preparation drills), new buildings.

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New buildings - earthquake proof

Counterbalancing weights on roof

cross bracing to provide extra support

deep foundations

shock absorbers in foundations

cover over areas immediately outside for falling materials

several emergencies stair cases

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