Tectonics revision notes

some notes to help with the AQA GCSE

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Tectonics
Seismic ­ movement of earth's crust
Structure of earth, inner core, outer core, mantle, crust
Core is a ball of solid iron and nickel; it is surrounded by the mantle of semi-molten rock that moves very
slowly, outer layer is crust which is very thin (20km). Crust divided into plates made up of two types of
crust
Oceanic crust is thinner and more dense
Continental crust is thicker and less dense
Plates move as rock underneath moves,
Boundaries ­ where plates meet (also called plate margins/boundaries).
Constructive plate boundary, plates pull away from each other, magma comes out
Destructive plate boundary, oceanic plate subducts under continental, pacific and Eurasian
Conservative plate boundary, plates slide along past each other, pacific and north African
Collision plate boundary, two plate of same type meet, indo Australian and Eurasian if two continental bits
meet then it makes fold mountains
Fold Mountains
Formed when tectonic plates collide and the sedimentary rocks that have built up between them are folded
and forced upwards to form mountains
Formed at destructive plate boundaries and places where there used to be destructive plate boundaries
Can be when continental and oceanic plates collide (Andes) or just when two continental plates collide
(Himalayas)
Higher slopes used for grazing animals
Lower slopes for crops
Steep slopes sometimes terraced to make growing crops easier
Mining - steep slopes make access difficult so zigzag roads are carved out on the sides of
mountains to get to them
Hydro-electric power(HEP)- steep sided mountains and high lakes make ideal for generating it
Forestry ­ good environment to grow some types of trees (e.g.) conifers, grown on steep valley
slopes and used for things like fuel, building materials and to make things like paper and furniture
Tourism ­ have spectacular scenery. In winter sports such as skiing, snowboarding. Summer walking,
tunnels drilled through to make straight fast roads improving communications for tourists and
people in area as quicker to get to places
Ocean trenches are formed in a similar way to fold mountains except with two oceanic plates colliding and
folding downwards

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Alps ­ Fold Mountain Case Study
In central Europe, stretches across Austria, France, Germany, Italy, etc
Formed about 30 million years ago by collision between the African and European plates
Tallest peak is Mont Blanc at 4810 on Italian- French border
12 million people
Used for
Farm goats for milk cheese and meat
Sunnier slopes terraced to plant vineyards
100 million tourist visit a year
70% of tourists visit in winter for skiing etc
Summer visit for walking, mountain biking, paragliding, climbing
New villages built…read more

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Advantages for living near volcanoes ­ soil fertile, geothermal energy, building materials, tourism, scenery,
minerals, mining
Mt St Helens- Volcano Case Study
Location: - west coast of north America on the ring of fire and the cascade mountain range
Causes of eruption: - Juan de fuca plate (oceanic) is subducting beneath North American plate (continental)
Sequence of events:-
1. Normal composite volcano
2. Bulge appears on North-facing side in early May 1980 (prior to this earthquake
had been experienced since March)
3.…read more

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Supervolcanoes are mainly in the northern hemisphere with two in the southern hemisphere, there are 3
quite close to each other in the USA there are 2 of the coast of Asia and two off Australia 7 in total
See PowerPoint
How formed
1. Rising magma can't escape and a large bulge appears on the surface
2. Cracks appear in the surface and gas and ash and lava erupt from the magma chamber
3.…read more

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Measure magnitude (how much energy) Measures intensity (how much damage)
Uses a seismometer to measure Uses people's opinions, eyewitness
statements, surveys to measure
Scientific scale Good for initial damage
Easier to compare Objective
Standardised scale You don't need technology and can use
historical data
Logarithmic scale:
1=1
2 = 1x10 = 10
3 =2x10 = 100
4 = 3 x10 = 1000
Case studies
Kobe, Japan 1995 17th January 5.46 Sichuan, China 12 may 2.…read more

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Tsunamis are earthquakes under the sea, a plate is getting pushed down under another plate and just
suddenly jerks back up displacing a large amount of water upwards. An example is the Boxing Day Indian
ocean tsunami between the indo Australian and Eurasian plate colliding
Case Study - Tsunami
Indian Ocean Boxing Day 2004
Earthquake off west coast of Sumatra that was 9.1 of Richter scale.…read more

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