Plate Tectonics

Geography Revision on Plate Tectonics with some case study notes

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  • Created by: Lex
  • Created on: 30-03-10 16:06
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Plate tectonics
1. Radioactive decay in the core causes heat radiation 1200'c
2. Molten rock is heated and rises
3. Semi-molten rock spreads, driving the plates
4. Movements of current = direction of plate
5. Rock cools, more dense and sinks
6. Reheated and travels back up (less dense)
7. Causes a cycle or convection current, taking over 200 million years
Types of Crust
Continental SIAL, 3 billion years old, composed of granite, 20-80 km thick
Oceanic SIMA, 70-100 million years old, composed of Basalt, 10 km thick
Constructive plate boundary
Divergent plate boundary ­ move away from
each other
Sea allows quick cooling of hot magma
Volcanic island ­ pokes out of sea
The crust on either side of the margins is
often faulted
Forms shield volcanoes
1. Convection currents in mantle cause two plates to move apart
2. Earthquakes are caused by the friction of the plates moving apart
3. Magma rises to fill gap, forming volcanoes as it cools
4. More magma rises up through the middle
Destructive Plate boundary
Convergent (compressional) plate boundary

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Oceanic Plate moves due to convection currents
2. Subduction zone ­ oceanic crust is heavy and sinks under continental plate
3. Rock melts due to friction and heat from mantle. Friction also causes earthquakes
4. Melted rock rises taking water with it, making it less dense
5. Edge of continental crust folds and buckles when it
gets squashed
6. Increase in size and pressure, causes fold mountains
to form
7.…read more

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Rising magma causes swelling and bulging of the volcano ­ tiltmeter or GPS ­
satellite detects movements
Seeping gas
Gurgling and belching noises
Fold Mountains
Formed by folded sedimentary rock
Found at convergent boundary
Examples = Alps, Rockies, Himalayas
1. Sediments settles in depressions on the seabed,
called Geosynclines
2. This becomes compressed to form sedimentary rocks
3. More layers of sediment form and the plates start to move together
4. Sediments becomes crumpled and folded
5.…read more

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Winter sports ­ resorts like Avalanches ­ constant
Chamonix = tourism = threat, money spent to
economy prevent them
Agriculture ­ south facing Climate ­ cold and wet , Cereals, sugar beet, vines
slopes e.g. industrially and agriculturally and fruits
Himalayans/Nepalese people difficult (machines can't
operate, short crop growing Transhumance ­ movement
season) of cattle in different seasons
e.g. Alps
Forestry ­ coniferous woods Mountainous regions ­
for building and fuels e.g.…read more

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Place Info Primary effects Secondary effects
Borders India and Badly built buildings Crops survived,
LEDC Pakistan collapsed markets re-opened,
Kashmir 7.6 R. Scale 79, 000 killed jobs for farmers
Earthquak 60 seconds long 100,000 injured Office/shop damage
8:40am, 8th Oct 05 3.…read more

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Chances Peak 50% population returned to the
eruption in July 1955 evacuated to north of island
Plymouth Brades the island
N & S American Forest fires
plates vs Caribbean
Expanding lava
dome + large
pyroclastic flow…read more

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Factors affecting severity of an earthquake
Aid sources
Response times of emergency services
Technology (e.g. quakeproof buildings )
Geographical Location ­ near boundaries, import of aid...
Economic Status ­ money for repairs...…read more


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