Restless Earth

Restless Earth

Tectonic Plates
1. Destructive margins
  1. Subduction, oceanic subducts under the continental
  2. Where an oceanic and a continental plate meet
  3. Oceanic is forced down into the mantle and is destroyed
  4. This often creates volcanoes and ocean trenches
  5. When two continental plates meet eachother them smash together but no crust is destroyed
2. Constructive margins
  1. When two plates are moving away from each other
  2. For example mid-Atlantic ridge
  3. Magma then rises from the gap and cools creating a new crust
3. Conservative margins
  1. When two plates are moving sideways past each other or moving in the same direction at different speeds
  2. Example, west coast of USA
  3. Crust isn't created or destroyed
  4. Main cause of erthquakes
Fold Mountains
1. Formed when plates collide at destructive margins
2. When plates collide the sedimentary rock that has built up between them is folded and forced upward
3. Found at both oceanic and continental such as in the Andes as well as continental and continental as seen in Himalayas
4. These areas have lots of very high mountains, which are very rocky and are steep sloped and they are usually snow topped and have glaciers
5. Uses for fold mountains Case Study:Andes
  1. Farming
    1. Higher mountain slopes aren't good for growing crops so instead they're used for grazing animals such as the mountain goats
    2. Lower mountain slopes are used to grow crops, however crops can be grown on terraces higher up
  2. Mining
    1. They fold mountains are a major source of metal ores
  3. Hydro-electric power
    1. Steep sides mountains and high lakes are blocked using a dam and this creates a huge lake, this can be used for drinking water or electricity
  4. Forestry
    1. Good environments to grow some trees such as conifers
    2. They're grown on steep valley slopes and are used for fuels, building materials, furniture and paper
  5. Tourism
    1. The mountains offer spectacular views, this attracts tourists
    2. In winter it brings in trade from skiing, snowboarding and ice climbing
    3. In summer money comes from walkers, who enjoy to walk in the scenery
    4. Roads and tunnels have been made through the mountains to improve access to tourists and locals
6. Disadvantages of fold mountains
  1. Steep relief
  2. Poor soils
  3. Limited communications
7. Mount Everest at 8850m
Volcanoes
1. Are formed at destructive and constructive plate margins
2. 3 different types of volcano
  1. Shield
    1. Made up of only lava
    2. The lava is less viscous and moves quickly and spreads over a wide area
    3. Forms a low, flat volcano
    4. Mauna Loa on the Hawaiian islands
  2. Dome
    1. Made up of only lava
    2. The lava is thick, flows slowly and hardens quickly
    3. Forms a steep sided volcano
    4. Mount Pelee in Caribbean
  3. Composite
    1. The lava is usually thick and moves slowly this hardens quickly to give a steep sided volcano
    2. Made up from ash and lava that has erupted and hardened into layers
    3. Mount Fuji in Japan
3. Tiny earthquakes and escaping gases and the shape of the volcano are tell tale signs of a likely eruption
4. Formation of a volcano
  1. Oceanic plate subducts into the mantle where it's melted and destroyed
  2. This increases the pressure and a pool of magma forms
  3. Magma rises through the cracks in the crust called vents
  4. /the magma erupts onto the surface forming a volcano
5. Supervolcanoes
  1. Characteristics
    1. Flat
    2. Cover large area
    3. Have a caldera
  2. Formation of a supervolcano
    1. Magma rises up through the cracks in the crust to form a large magma basin below the surface
    2. The pressure of the magma causes a circular bulge on the surface several km wide
    3. The bulge eventually cracks, creating vents fro the lava to escape through
    4. The lava erupts out of the vents causing earthquakes and sending gignatic plumes of ash and rock
    5. As the magma basin empties, the bulge is no longer supported and collapses, expelling more lava
    6. After the eruption a large crater is left (a caldera), this sometimes fills with water and form a large lake such as Lake Toba in Indonesia
    7. Only happen in a handful of places, at destructive plate margins or over parts of the mantle called hotspots
  3. Last eruption, Lake Toba 74 000 years ago
  4. Consequences of eruption
    1. Throws out 1000s of cubic kilometres of rock, ash and lava. A normal volcano will only send out around 1 or 2 kilometre cubed
    2. A thick cloud of superheated gas and ash will flow at high speed, killing, burning and burying everything with a huge radius.
    3. Ash will shoot out over whole continents, blocking the sun out and could trigger a mini ice age
    4. Ash will settle 100s of kilometres away and burying fields and buildings. A normal volcano only cover a couple of square kilometres
  5. Case Study: Yellowstone
6. Case Study: Mount St. Helens
  1. May 18th 1980
  2. 57 deaths
  3. $2-3bn
  4. An earthquake (5.1 magnitude) caused the entire north side to slip away
  5. Blast cloud traveled 17 miles
  6. Depressurized the volcano's magma system, this triggered huge explosions
  7. The landslide traveled 14 miles down a river
  8. 200 housers, 27 bridges, 15 miles of railways and 185 miles of roads were sestryoed
  9. Set up a speed limit of 15mph around the area pre eruption
  10. People were evacuated and roads closed pre eruption
  11. USA, MEDC
7. Case Study: Nyamuragira (Congo)
  1. 17 January 2002
  2. Congo, LEDC
  3. Evacuation of more than 300,000, a late evacuation
  4. Aid agencies from MEDCs provided short term aid such as food and shelter but not so much longer term aid due to the political instability in the DRC
  5. Failed to prepare for the eruption, tremors were felt weeks before but were not acted on
  6. Only acted when large plums of smoke appeared
  7. Massive lava flows
  8. 80& of its commercial infrastructure destroyed around the area
  9. 120,000 people left homeless
  10. Many fled to neighbouring Rwanda, LEDC, they couldn't cope with the amount of people
  11. Evacuees had no water or electricty
  12. Looters
  13. Little support for the clean up effort
Earthquakes
1. Earthquakes occur at all three plate margins
  1. Destructive margins: tension builds up when one plate moves and gets stuck as it's moving down into the mantle
  2. Constructive margins: tension builds along cracks with the plates as they move away from each other
  3. Conservative margins: tensions build when the plates become stuck when trying to move past each other
2. Two ways of measuring Earthquakes
  1. The Richter scale
    1. Measures the amount of energy released by an earthquake (the magnitude)
    2. Magnitude is measured using a seismometer
    3. It's logarithmic and doesn't have an upper limit, this means that a 5 on the scale is 10 times more powerful than 4 on the scale
    4. Most people don't feel an earthquake with a magnitude of 1-2, major earthquakes are 5+
  2. The Mercalli
    1. Measures the effects of an earthquake
    2. Effects are measured by asking eyewitnesses for observations of what happened, through words or images
    3. On a scale of 1 to 12
3. How they occur
  1. Earthquakes are caused by built up tension
  2. When the pressure becomes too much, the plates snap past each other, this sends out shock waves (vibrations). These vibrations are the earthquake.
  3. These shock waves spread out from the focus, the point of origin of the earthquake from within the crust.
  4. Nearer the focus, the more powerful the waves and this causes more damage
  5. The epicentre is the point on the surface of the earth, straight above the focus, where the earthquake originated from
  6. Weak earthquakes are common and strong earthquakes are much more rare
4. Case Study: Kobe
  1. 17th January 1995
  2. 7.2 magnitude
  3. Lasted 20 seconds
  4. Kobe population of 1.5m
  5. Social
    1. 6,434 died
    2. 250,000 homeless
    3. 25,000 injured
  6. Economic
    1. $100bn
    2. 2.5% of Japans GDP
    3. Only 3% of the buildings in Kobe were insured for earthquakes
    4. Sixth largest container port in the world
    5. Destroyed 150,00 buildings
    6. Destroyed 120 out of 150 quays in Kobe
  7. Local responses
    1. Local hospitals struggled to keep up with demand for medical treatment, this was through the collapsed or obstructed roads this meant they couldn't reach the most affected area
    2. People were operated on in waiting rooms and corridors due to the overcrowding
    3. 1.2m volunteers were involved during the relief efforts in the first 3 months
    4. NTT and Motorola provided free service for victims
5. Case Study: Haiti
  1. 12th January 2010
  2. 7.0 magnitude
  3. Social
    1. 3,500,000 people were affected
    2. 220,000 died
    3. 300,000+ were injured
    4. 4,000 schools destroyed or damaged
    5. 1,000,000 left their homes
    6. Cholera outbreak a secondary affect
  4. Aftershocks of 5.9 and 5.5 magnitude
  5. Slow aid response
  6. LEDC
  7. Massive damage of roads and buildings
  8. Government to poor to rebuild
Tsunami
1. A special type of wave where entire depth of the sea or ocean is set in motion by an event, often an earthquake , which disiplaces the water above and creates a huge wave
2. Tsunami genesis, is the formation of a tsunami. They are often found at destructive plate boundaries when the plate snaps.
3. Case study: Indonsia
  1. Social
    1. 70% of all coastal populations near the epicentre, such as Banda Aceh, were killed or missing
    2. People were swept away from beaches in Renang, Malaysia
  2. Environmental
    1. Dozens of buildings were destroyed in the initial earthquake in Banda Aceh, before the flood waters hit
    2. In India, arable land, such as rice fields and crops were destroyed by the influx of water
    3. Saltwater contaminated fresh water sources killing freshwater fish, Andaman Islands, India
    4. Sri Lanka, part of Colombo was shut by flash floods affecting business
  3. Economic
    1. Tourist numbers fell after worries of this happening again, tourism is a lifeline in many parts of SE Asia
    2. Homes and businesses were destroyed with some whole towns being flattened, especially in Indonesia
    3. Crops were destroyed in Sri Lanka, these are a large income to the area
  4. LEDC
  5. 9.1 or 8.9 magnitude
4. Case study: Japan
  1. MEDC
  2. Economic
    1. Infrastructure destroyed
    2. Loss of jobs
    3. £133bn
  3. 9.0 magnitude
  4. Fukushima nuclear plant
    1. Reactors exploded
    2. Worst nuclear incident in 25 years
    3. Massive damage
    4. Secondary affect
  5. 11th March 2011
  6. 138,000 buildings destroyed
  7. 465,000 evacuated
  8. 16,000 dead
5. Short term effects
  1. No food
  2. No clean water
  3. Communications
  4. Lack of medical aids
  5. Ports and roads closed
  6. Spread disease
  7. Deaths and injuries
  8. Fires
  9. Destroyed buildings
  10. Gas and electricity supply affected
6. Long term effects
  1. Debt to other countries- from borrowing money to rebuild
  2. Need to rebuilding of homes and entire towns
  3. Need for stronger more 'earthquake proof' houses
  4. Need for emergency evacuation plans for families
  5. Spread of disease - may run through generations
  6. Demand for jobs in the construction industry for the rebuilding to take place

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	Created by Stephen Booth about 11 years ago