Geography- Dynamic Planet - Restless Earth

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  • Created by: Em_New99
  • Created on: 16-05-15 13:54

The Earth in Cross-Section

Lithosphere

  • Continetal Crust -Solid State, Composed of Granite, Temprature up to 900°c, 25km-80km thick
  • Oceanic Crust -Solid State, Composed of Basalt, Temprature up to 900°c, 6km-8km thick

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Mantle

  • Asthenosphere -Partially Molten State, Composed of Peridotites, Temprature from 1000°c- 1600°c
  • Mantle- Solid State, Composed of Silica-based minerals, Temprature from 1600°c- 4000°c

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Core

  • Outer Core- Liquid State: Very Dense, Composed of Iron/ Nickel, Temprature from 4000°c- 5000°c
  • Inner Core- Solid State: Very Dense, Composed of Iron/Nickel, Temprature from 4000°c- 5000°c
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How the Earths Tectonic Plates Move

  • High tempratures caused by gradual radioactive decay creat rising limbs of material in the mantle called convection currents.
  • These cool and rise before sinking again- like a lava lamp.
  • Some of the material moves in sheets creating movements in the crust above it, which is pulled apart to form new crust or hotspots.

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Constructive/ Divergent Plate Boundary

Contstructive Margins

  • Formed by rising magma spliting the continental crust and forming new oceans
  • EXAMPLE- The Eurasian Plate is seperating slowly from the North American Plate. This creates the mis-Atlantic ridge.
  • Volcanoes and earthquakes can form

(http://www.coolgeography.co.uk/GCSE/AQA/Restless%20Earth/Tectonics/Constructive_Margin.png)

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Destructive/ Convergent Plate Boundary

Destructive Margins

  • The denser basaltic oceanic plate sinks beneath the continental plate.
  • This is known as subduction and creates a deep ocean trench near the line of contact between the oceanic and continental plates
  • As the oceanic plate subducts it builds pressure and temprature in the mantle
  • This causes some lightweight material in the mantle to rise and form volcanoes
  • The collision of plates also lifts and buckles the cotinental plate causing fold mountains 
  • Earthquakes could also form.
  • (http://upload.wikimedia.org/wikipedia/commons/2/29/Active_Margin.svg)
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Conservative Plate Boundary

  • Plates slide past each other or move in the same direction but at different speeds 
  • This could mean that no crust is formed or destroyed and volcanoes do not form
  • Great strain builds up along the junction with sudden lurches along the fault
  • Earthquakes are frequent and often large
  • EXAMPLE- San Andreas fault

(http://www.discoveringgalapagos.org.uk/wp-content/uploads/2014/09/g2a1_conservative-edit-2.png)

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Different Hazards and their Causes

The impact of any hazard, including earthquakes and volcanoes depends on:

  • The size of the event
  • Vunerability of the population- Poverty and high density of people
  • Capacity of the population to cope- How prepared they are
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Impacts of Earthquakes

Factors which determine the severity:

  • Magnitude on richter scale
  • The depth (Shallow=more destructive)
  • The distance from epicentre
  • The time of day
  • Level of preparedness
  • Quality of the emergency services

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Definitions 

Primary Impacts- Immeidate effect 

Secondary Impacts- The impact on properties and people after the earthquake has finished. Lack of supplies ect

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Types of Volcanoes

Different types of volcanoes

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Composite

  • Steep-sided, small area, alernate layers of ash and lava.
  • Viscous/sticky lava- flows slowly
  • Infrequent explosions and sometimes unpredicatble 
  • Pressure builds up over time
  • EXAMPLE- Mt Pinatubo

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Shield Volcanoes

  • Gentle slopes, large area, almost all lava
  • Fluid flows quick
  • Basaltic magma
  • Very frequent and generally gentle eruptions
  • EXAMPLE- Mauna Loa (Hawaii USA)
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Prediction and Warning- Volcanoes

Volcanic eruptions can be predicted if the right equiptment is in place

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  • Gas emissions, earth tremors and 'bulging' of volcano's flanks can be meaured and used to predict eruptions
  • Seisomemeter- Measures the movement in the earth (seismic waves)
  • Tilt meters- Measure bulging of volcano
  • Thermal imaging techniques to see heat around the volcano
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Prediction and Warning- Earthquake

Predicition Methods

  • Seisometer- Used to pick up vibrations in the earth
  • Laser Beams can be used to detect plate movement

Preperation Methods

  • Emergency plans
  • Well-trained and well funded emergency services
  • Warning systems
  • Evacuation routes
  • Hazard resistant buildings
  • Disaster kits
  • Landuse planning
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