Plate Tectonics Flashcards
Details on the core
Inner core is solid
Outer core is semi-molten
Contains iron and nickel
6,000°C
Details on the mantle
Rigid nearest the core
Asthenosphere is molten and in the middle of the mantle
Rigid nearest the crust - Moho discontinuity
Details on the crust
Continental
- 30-70km thick
- less dense
- Sial
Oceanic
- 6-10km thick
- more dense
- Sima
What is the earth’s main source of internal energy?
Heat
Where is the earth’s heat derived from?
Some is left over from when the earth was formed
Some comes from radioactive decay from things such as uranium
How do convection currents cause plates to move?
The earth’s mantle is hottest closest to the core, this causes lower parts of the asthenosphere to heat up, become less dense and rise.
As they get to the top of the mantle, they cool down and sink. This process creates circular motions known as convection currents.
These convection currents create drag on the base of the plate, causing them to move
How does slab pull cause plates to move?
At a destructive plate margin, the denser crust is forced under.
The sinking of the plate, aided by gravity, pulls the rest of the plate towards the boundary
How does ridge push cause plates to move?
At a constructive plate margin, magma rises to the surface and forms new crust.
The new crust cools down and becomes denser
Gravity causes the denser rock to move downwards
This puts pressure on the tectonic plates and causes them to move apart
Explain the process of sea floor spreading
As tectonic plates move apart, magma rises up to fill the gap and then cools to create new crust
Over time, the new crust is pulled apart and more new crust forms.
This leads to the sea floor becoming wider and wider
This can create mid ocean ridges
I this process occurs on land, this creates rift valleys
