Crust, Currents, Plates Flashcards
What is the earth made from, 4 things?
Inner core
Outer core
Mantel
Crust
What is the lithosphere?
The solid top layer of crust in which plates are formed, consists of crust and upper mantel
What is asthenosphere?
Soft, plastic like rock in the upper mantel just below the lithosphere
What is the earths core temperature roughly?
5000 to 7000 degrees Celsius. That’s about as hot as the surface of the sun, but vastly cooler than the suns interior
What’s the first stage of convection currents in the mantle?
Heat source- radioactive decay in the earths core (iron + nickel)
What is the second stage of CC ?
The heat cools and sinks back down to be reheated
What is the third stage of CC?
Semi molten rock spreads out carrying the above plate with it
What is the forth stage of CC?
Direction of plate movement due to convection current below ( <— —>)
What is the fifth stage of CC?
The rising limb of convection current. Heated rock in the mantle rises as it is less dense
What is slab pull?
At subduction zones gravity “pulls” the oceanic plate down into the mantle. This destroys crust material and keeps the earth in shape
What is ridge push?
The process of material pushing out from the ridge
Thickness of continental crust vs oceanic
30-70 km thick vs 5-10 km
Age of continental crust vs oceanic
As old as 4 billion vs 200 million
Density of continental crust vs oceanic
2.7g/cubic cm vs 3g/cubic cm
Mineral content to continental crust vs oceanic
Silicate and oxides vs silicate and magnesium
Rock type of continental vs oceanic crust
Granites vs basalts
What are the 5 evidences of plate tectonics?
Jigsaw fit
Geological fit
Fossil evidence
Tectonic fit
Paleomagnetism
What is paleomagnetism?
Paleomagnetism is the study of the record of Earth’s magnetic field preserved in rocks and sediments. It helps scientists understand the history of the Earth’s magnetic field, including pole reversals and past movements of tectonic plates
What is a constructive plate boundary?
2 plates are moving apart creating a gap in the middle for magma to rise up through.
Volcanoes form here but don’t erupt with force as the magma escapes quickly
Earthquakes occur e.g. mid Atlantic ridge
Rift valleys occur as land fall into the space left as plates move apart
What is a destructive plate boundary?
Dense oceanic plate descends below less dense continental plate.
As the plate descends it is melted due to friction with the continental plate, forming hot, liquid magma, which rises through cracks in the continental plate and form volcanoes as it reaches the surface
What is a collision plate boundary?
Occurs when two plates of similar densities move together i.e. a continental with another continental. This causes the material between them to buckle and rise up, forming fold mountains. E.g. the Himalayas (chain of fold mountains), they have been formed by the African plate colliding into the Eurasian plate
What is a conservative plate boundary?
When two plates slide past each other along a fault (weakness).
No volcanoes occur here but earthquakes do occur.
Example includes the San Andreas fault in California
