The Restless Earth
- Created by: Han2812
- Created on: 03-06-13 09:44
Types of Plate Boundaries
Conservative Plate Margins:
- Plates slide past each other (going past each other)
- Can cause really large earthquakes if plates get stuck
- Eg. San Andreas Fault (Californa), boundary between North American and Pacific Plate
Destructive Plate Margins:
- Plate push against each other
- Cause earthquakes, COMPOSITE volcanoes, fold mountains and ocean trenches
- Eg. The Andes, (South America), Nazca and South American Plate
Constructive Plate Margins:
- Plates pulling apart from each other
- Can cause earthquakes, SHIELD volcanoes and volcanic islands
- Eg. The Mid-Atlantic Ridge (goes through Iceland), boundry of N.American and Eurasion plate
Formation of Types of Volcanoes
Sheild Volcanoes:
- CONE SHAPE, WIDE BASE, GENTLE SLOPES, MADE OF LAVE, REGULAR ERRUPTIONS, LAVE POURS OUT WITH NO VIOLENCE
- Plates move apart, magma rise upwards from the mantle to fill the gap
- This adds new rock to the spreading plates
- Some maybe be forced to go to the surface through the vent
- If an underwater volcano grows high enough, can form volcanic islands eg Iceland
Composite Volcanoes:
- TALL CONE, NARROW BASE, STEEP SIDES, ALTERNATE LAYERS OF ASH AND LAVA, IRREGULAR WITH DORMANT PERIODS, VIOLENT EXPLOSIONS POSSIBLE
- Plate collide, denser oceanc plate is pushed down into the mantle, get melts in the subduction zone and forms a pool of lava
- The heat and pressure may force the magma along a crack where it errupts at the surface and forms a volcano
- Eg. Krakatoa in Indonesia
Supervolcanoes
What are they?
- Huge volcanoes, that errupt with at least 1000 km3 of erruptable material
- It forms a depression, called a caldera
- They errupt infrequently,1000s of years apart, have very large and violent eruptions if they do
- The effects are felt globally, with the ash affecting the land around and the atmosphere above, having significant and long term effects across the world
Formation:
- Magma cannot escape to the surface and collects under the lower crust
- An 'uplifted bulge' begins to form under the lower crust as the magma chamber enlarge
- Cracks appear on the surface. Gas and ash erupt from the magma chamber through these cracks
- Yellowstone, Yellowstone National Park, USA - its depression is 55km by 80k wide
Fold Mountains
Land Use of Fold Mountains - European Alps
Farming:
- Dairy - moving cattle to higher Alps in summer (grass) and feeding on hay in the winter
- Today cable cars bring milk down to the valley floor
- Also buys foodstuff for cattle to stay on valley floor all year round
Forestry:
- On North facing slopes - cuting down of coniferous trees
- Use wood for buildings and fuel, to make pulp and paper
Tourism:
- All year round (skiing, snowboarding, climbing, walking etc)
- Hotels, restuarants, ski lifts etc build on flat land of the high alps - helps economy
- Promblems: warming up means less snow, more skiers - worn slopes/soil erosion
HEP (Hydroelectric Power)
- Steep slopes, high rainfall, snow melt = fast flowing rivers, ideal for HEP
- Narrow valleys can be dammed, lakes can store the water
- Cheep HEP - used for industry eg, saw mills, aluminium smelting. Sold to other countries
- No minerals but high population is wealthy so technology can be used to develop the area, eg, electric railways, cable cars, build tunnels etc, allowing more tourism
Earthquake Case Studies - Japan
MEDC - Japan, March 11th 2011
Epicentre: 30 miles of the East coast of Japans largest island
Time: 2.46 pm
Magnitude: Richter Scale - 9.1 Mercalli Scale - IX
Plates involved: Pacific + Eurasion plates, DESTRUCTIVE plate boundary
Primary Effects: 15,854 deaths, some buildings collapsed but mostly stayed standing
Secondary Effects: Tsunami - waves up to 40m hight, flowed 6 miles inland, Fukashima nuclear power melt down, over 1000 aftershocks
Immediate Responses: Warning + evacuation of coastal areas due to good warning systems, many countries gave emergency aid
Long Term Responses: Rebuilding of destroyed towns, costing $122 billion, building of larger tsunami walls
Earthquake Case Studies - Haiti
LEDC - Haiti, 24th January 2010
Epicentre: 16 miles west of the capital Port-au-Prince
Time: 4.53 pm
Magnitude: Richter Scale - 7 Mercalli Scale - X (10)
Plates Involved: Caribbean + North American Plate, a CONSERVATIVE plate boundary
Primary Effects: 316,000 dead, 300,000 injured, 1 million homeless people. Major buildings in Port-au-Prince were destroyed - Presidential palace, parliment, cathedral, UN building, jail
Secondary Effects: 1 million people living in shelters, shortages of food. Disease - cholera, especially in refugee camps. Hospitals overwhelmed. Economy collapsed
Immediate Responses: Emergancy Aid given from MEDCs. USA took control of rescue effor as Haiti govement had been killed
Long Term Responses: $5.3 billion has been pled by MEDCs (USA, UK) to rebuild the capital
Tsunami Case Study - Japan Tukuku 2011
Causes:
- Earthquake magnitude (9.1) - slippage on Paific ocean floor, causing it to fall by 10m
- Water is displaced, wave moved west towards Japan and across the pacific
Effects:
- Breached sea walls, flooded 10km in land
- killed estimate 20,000
- knocked out the Fukushima nuclear power plant
- production slowed (honda - swindon)
Responses:
- immediate alerts sent via tv, phones, radios etc, costal areas were warned,
- safe places were identified and drills were paracticed every 3 months, so people knew what they should do
- buildings constructed to withstand earthquakes
- sea walls were build around 40% of japan coast to defend against tsunamis
BUT....
- Earthquake waas bigger than predicted, tsunami was taller than predicted, protective measures werent that good so massive scale of damage + relativly high death toll
- 2 year afterwards, nuclear power plant is still too dangerous to enter
Other Key Terms
Lava: Molten rock on the surface
Acid Lava: High viscosity, moves slowly, thick, from composite volcanoes
Basic Lava: Runny, love viscosity, moves fast, from shield volcanoes
Magma: Molten rock, found in the crust/mantle/volcano
Crust: Hard rock, cracked into different tectonic plates
Oceanic Crust: Made out of basalt, more dense, averages 5 km in thickness
Continental Crust: Made out of granite, less dense, averages 30 km in thickness
Mantle: Closer to the surface, molten rock
Core: In the centre of the earth, Temp 5500 degrees, solid rock
Crater: Opening of a volcano, where the lava comes out
Vent: Vertical cut/gap in a volcano that magma rises through to the surface
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