tectonics Flashcards
what are the different plate boundary’s ( A level terms also )
conservative (Transform)
constructive (divergent boundaries)
collision (convergent boundaries)
destructive (convergent boundaries)
what is the seismic activity like on the plate boundaries
constructive = shallow focus, usually low magnitude (5-6)
destructive = range of focal depths from shallow to around 700km along Benioff zone. High magnitude ( 8-9 )
collision = shallow to intermediate focus, moderate magnitude (6-8)
conservative = shallow to intermediate focus moderate magnitude (6-8)
what are the features on the plate boundaries
constructive = island arch, oceanic trench
destructive = fault lines ridges and surface scarring
collision = fold mountains and plateaus
transform ocean ridge and narrow alleys
what is slab pull
Older, cooler plates sink at subduction zones, as they cool they become more dense than the underlying mantle. The cooler subducting plate pulls the warmer plates along behind it
what is palaeomagnetism
every 200,00 to 300,000 years the magnetic field swaps and by this we can see how old the crust is via the magnetic stripes
what happened in India in 2001
there was a intraplate earthquake which was 7.7 and caused 13000-20,000 deaths
how do intraplate earthquakes happen
they can occur when pressure builds up in the middle of the plate since the plates move over a spherical surface zones of weakness can be created. When it releases it can cause an earthquake
What are the tectonic theory’s
jigsaw fit theory
fossil evidence
dating oceanic crust
observing fault lines
images of ocean crust
mineral deposits
what happens in the jigsaw fit theory and the fossil evidence
jigsaw = Different continents around the world can fit together like a jigsaw e.g south america and africa
fossil= fossils of species such as plant and mamal found in one continent but also another e.g species called lystrosaurus found in antarica,india and africa
what happens in the dating ocean crust and observing fault lines evidence
dating ocean crust = Happens via palaeomagnetism allowing us to age the rock. Youngest rock found around south America and Africa. Form on constructive plates and via slab pull
observing fault lines = By pictures where you can see obvious movement in the land such as cracks and shifts. Most likely a conservative plate boundary
what happens in the images of the oceanic floor and mineral deposits evidence
images of oceanic floor = see where new land has been created via constructive plate margins where magma has rose
mineral deposits = limestone sedimentary rock was found around India and also discovered around Greenland
why are the theory of tectonics important
it proves that Pangea may have existed and shows us how our plates move
Describe P-waves
Primary wave
- quickest wave
- ground moves up and down
- Can travel through solid liquid and gas
- Is a body wave
the wave goes side ways and compresses and expands
Describe an S-wave
secondary wave
- Ground moves back and forth
- Arrives after p-waves
- slower
- Can only travel through solids
- High amplitude
- body wave
S- waves move like waves on a beach up and down but the ground goes side to side
