plate tectonics Flashcards
which way do divergent/constructive plates move?
apart
which way do convergent/destructive plates move?
towards eachother
what substances make up the core?
iron and nickel
why is the inner core a solid?
due to the pressure acted upon it from the atmosphere and earth.
what are the main sources of earths internal heat?
extraterrestrial impact
gravitational contraction
frictional heating
radioactive decay of uranium
what is extrusive rock
rock that is solidified outside of the earths surface, eg basalt
what is intrusive rock
rock that has solidified under the earths surface, eg granite
describe felsic rock
high in light coloured minerals such as quartz and feldspar
describe mafic rock
high in dark coloured minerals, mainly comprised of magnesium and iron.
what is formed when two continental plates converge?
a rift valley
what happens when oceanic plates move apart?
deep faults in the ocean form, cold seawater percolates down through the small gaps and is superheated through contact with the magma.
how deep is the mantle?
2885 km deep
how thick is the crust?
typically 30km deep, however thick mountain belts can be up to 70km
where is earths magnetic field generated?
the outer core.
3 characteristics of continental plates
less dense granatic rocks
high silica content
major continents
3 characteristics of oceanic plates
thinner but denser,
dense basaltic rocks
sinks into the mantle with age
