Restless Earth

Created by: Eloise1239
Created on: 31-07-16 22:29

View mindmap

The Restless Earth
- Unstable Crust
  - Middle of the earth-core around that is the mantle, the top layer of the earth is called the crust.
  - 2 types of crust
    - Continental- less dense but thicker (30 km)
    - Oceanic- denser and thinner (5 km)
  - Tectonic Plates
    - 7 large tectonic plates and lots of smaller ones.
    - Some tectonic plates are: African , South American, Pacific
- Plate Margins
  - Conservative
    - Plates slide past each other.
      - Sometimes they are going the same way but at different speeds.
    - Feature
      - Earthquakes
  - Constructive
    - Two plates move apart, magma rises to fill the gap.
    - Features
      - Usually found under the sea.
      - Shield volcanoes.
      - Volcanoes can form islands if they rise above sea level.
  - Destructive
    - Plates move together.
    - Lighter continental crust stays onto while the denser oceanic crust is pushed down.
      - Pushed into the mantle where it melts.
    - Features
      - Composite volcanoes.
      - Earthquakes
      - Fold mountains
      - Ocean trenches
- Fold mountains and ocean trenches.
  - Ocean trench
    - Formed in the subduction zone.
    - One wall is formed by the subducting oceanic crust.
      - The other wall is the edge of the continental crust.
  - Fold mountains
    - Occur at destructive plate margins.
      - Alps, Himalayas and Andes
- Fold mountains Info
  - Alps
    - Summer tourism based on the scenery.
    - Livestock graze on valley floor.
    - Rich soil on valley floor so crops are grown there.
    - Travel, railway tunnels have been cut through the mountains to make travel easier.
    - Winter tourism based on skiing- steep snowing slopes.
    - Steep valley sides and fast flowing mountain rivers are perfect for HEP.
- Volcanoes
  - 2 main types of volcanoes, composite and shield.
    - Sheild
      - Runny lava
      - Regular and frequent eruptions
      - Not explosive
      - Gentle slopes and wide base.
      - Pours out smoothly.
      - Example Surtsey Island, near Iceland.
      - Magma rises to fill gap between plates.
    - Composite
      - Magma is forced up to the surface through cracks in the crust.
      - Viscous lava
        Violent eruptions.
        Example Etna, Italy
      - Cone shape, steep sides, narrow base.
      - Irregular eruptions with long dormant periods.
  - Supervolcano
    - 1000 times bigger than a normal volcano.
    - After an eruption the magma chamber collapses, forming a caldera.
    - Last known supervolcano was 75000 years ago.
- Volcanoes as hazards
  - Positive Impacts
    - Fertile Soils
      - Tourist Attractions
        Natural Hot Springs
  - Negative Impacts
    - Always Destructive (both types of volcano)
      - Global Destruction e.g Ash Clouds Disrupt Travel
        Unpredictable so its difficult to prepare for them
  - Primary Effects
    - People injured/killed
      - Buildings/ Farmland Destroyed
        Communications Desrupted
  - Secondary Effects
    - Costs of Rebuilding
      - Tourists Might Stay Away
        Ash Improves Soil Fertility
  - Case Study
    - Montserrat 1995-1997
      - In the Carribbean
        On a Destructive Plate Margin
      - Cause: Magma forced up through weak points in volcano.
      - Primary Effects
        20 people killed
        2/3 of homes destroyed and farmland
        5000 people evacuated
      - Secondary Effects
        Costs of rebuilding
        Tourist industry disrupted
      - Immediate Response
        Evacuation
        Emergency help to provide temporary shelters
      - Long-term Response
        UK aid to rebuild infastructure
        Volcano Observatory built to monitor volcano
        Attempt to re-attract tourists
  - Predicting Eruptions
    - 1. Tiltmeters - Check for bulges on volcanoes slope
      - 2. Satelites - Monitor changes in the heat activity
- Earthquakes
  - Facts
    - Can happen on all plate margins but most common on destructive plate margins
    - Features
      - Focus - Point where earthquake happens underground
        Epicentre - Point on surface above focus (effects of the shock the worst)
        Shockwaves - come out at all directions from the focus.
    - Higher number of deaths can be caused by a high density population or self built houses.
  - Measuring Earthquakes
    - Richter Scale - To measure the earthquakes magnitude from values 1-10.
      - Mercalli Scale - Measures its impact on people.
- Earthquakes hazards
  - Primary effects - straight after
    - Deaths injures
    - Damage to buildings
    - Damage to roads, bridges, railways
  - Secondary effects - afterwards
    - fires caused by broken gas pipes/ electricity pylons
    - Landslides
    - Spread of disease cause sanitation
    - Tsunamis
  - Immediate response
    - rescue teams
    - medical care
    - Road clearance
  - Long-term response
    - Improving emergency procedures
    - Practising drills
    - Earthquake proof houses/ buildings
- Tsunamis
  - Come after an earthquake.
  - How tsunamis happen
    - 1. Two plates get stuck and build up tension.
      - 2.Underwater earthquake happens as the tension breaks, bringing one plate upwards.
        3.Sea bulges upwards creating a huge swell of water.
        4.The swell reaches the coast and travels very fast inland.
  - Case Study
    - Asian Tsunami 2004
      - Caused by an earthquake underwater and the epicentre was off the coast of Sumatra, Indonesia.
      - Places that were effected- Sri Lanka, Indonesia, Thailand, India.
      - Over 220,000 people killed.
      - 500,000 houses destroyed.
      - Farmland ruined by the salt, tourism and fishing disrupted.

Get Revising

Restless Earth

Comments

Similar Geography resources:

Comments

Related discussions on The Student Room

Similar Geography resources: