Hazardous Earth - Tectonics Flashcards
what are the three main layers of the earth
crust, mantle and core
what is the Earth’s crust made up of
The crust is solid and rigid - made up of tectonic plates
what do tectonic plates move on top of
asthenosphere
what is the asthenosphere
a solid but “plastic layer” that’s under such high pressure that the rock flows
how hot are the lower layers of the mantle
it’s liquid magma at 3000degrees
what is the outer core made out of and what is the temp
Liquid iron and nickel - temp is 4,000-6,000
what is the inner core made out of and what is the temp
Iron - 5,000-6000. The pressure is so high that this iron is solid
how does convection currents help move plates
(1) The core heats up the molten rock in the mantle to create a convection current
(2) The heated rock from the mantle rises to the Earth’s surface
(3) At the surface, the convection current moves the tectonic plates in the crust
(4) Molten rock cools and flows back to the core to be reheated
What are the two main types of crust
Continental crust and oceanic crust
What is the Continental made up of mainly; what is oceanic crust made up of mainly
Continental = granite
Oceanic = basalt
Which is more dense - Continental or Oceanic
Oceanic
Are the Continental+ Oceanic crusts more or less dense than the rocks of the asthenosphere
Less dense
Which is the main heat source that powers convection - is it (i) magma (ii) radioactive decay (iii) continental drift or (iv) subduction
radioactive decay
Explain why radioactive heat is important to tectonics
Around half of the heat of the interior of earth is generated by radioactive decay (uranium and thorium) and this heat rises up through the mantle to power the convection process.
The other half of the earth’s heat, which is heat left over from earth’s formation, stays close to the core and is not involved in convection
