restless earth Flashcards
Name the two types of tectonic plate
Oceanic and continental
Name the 4 layers of the earth
Crust, Mantle, outer core, inner core
Which type of plate tectonic is more dense yet thinner
oceanic crust
Which layer makes the plates move?
The mantle
What are convection currents? Give detail. Mention core and mantle.
Inner core filled with radioactive decay which heats the magma in the mantle, magma in mantle becomes less dense and rises until it reaches near the crust. Where it then cools down and becomes more dense so it sinks back down again in a circular motion.
What happens at a destructive plate margin? (three things)
- two plates move towards each other
- oceanic (more dense) gets subducted under mantle and destroyed.
- This causes volcanoes and ocean trenches
What happens at a constructive plate margin? (three things)
- plates slowly move away from each other
- Magma rises from mantle to gill gap and cools (causing a volcano to erupt)
- new crust formed
What happens at a conservative plate margin? (three things)
- when two plates are moving sideways or in the same direction next to each other
- they move at different speeds
- crust isn’t made or destroyed
What happens at a collision plate margin? (three things)
- when two continental plate margins collide
- they are the same density so neither is subducted
- collide and create fold mountains
At what boundarie(s) do fold mountains formed and what rock type?
destructive/collision
sedimentry
Give an example of fold mountains made at a destructive plate margin? Collision?
Andes (south America)
Himalayas ( Asia)
What five things do humans use fold mountains for?
Farming, Hydro-electric power, mining, tourism and forestry
Talk about the fold mountain case study (6 things)
- population of 12 million
- 100 million tourists annually
- 70% for skiing etc
- 60% of power from HEP in Alps (Berne Switzerland)
- steep unland areas used to farm goats/sheeps
- salt/iron/gold/copper mining
How have the alps adapted to fit the landscape? (3 things)
Steep relief: goats farmed as they live on mountain side
Poor soils: Animals grazed in higher areas where soil is too poor for crops
Limited communications: Roads built over lower mountain parts, and tunnels made through mountain.
Which two plate boundaries are volcanoes found at?
Destructive, constructive
How is a volcano formed at a destructive plate boundary?
- oceanic plate subducted and melted
- magma forms in pool
- rises through cracks and vents
- magma erupts onto surface as lava forming volcano
How is a volcano formed at a constructive margin?
- magma rises through gaps as plates move apart
- forms a submarine volcano
- builds over time
- erupts
How else can a volcano be made?
If its over a hotspot
Describe the characteristics of a composite volcano.
- made up of ash and lava layers
- steep sided
- thick and slow lava
describe the characteristics of a shield volcano
- made up of only lava
- lava is runny and flows quickly
- spreads over a wise area so volcano is low and flat
describe the characteristics of a dome volcano
- made of only lava
- thick lava that’s slow
- steep sided volcano
Talk about the Soufriere Hills (Montserrat) volcano CS.
include primary/secondary effects and immediate/long term responses
- 19 killed in Harris village
- Atlantic subducted under carribean
- primary effects; capital buried under 12m of ash, 2/3 homes destroyed
- secondary effects: fires, 8000 people left (12,000 original), improved soil fertility
- immediate response; people evacuated, £17 million donated by UK of emergency aid
- long term responses; exclusion zone put in place
Where are super volcanoes found
destructive plate margin and hot spots
How is a supervolcano formed?
- magma rises through cracks, forms a magma basin
- pressure on magma causes a bulge
- bulge cracks leaving magma vents
- lava erupts causing earthquake and ash and rock plumes
- magama basin empties leaving caldera
