Earth structure & plate movement

Crust

• Surface layer - habitable
• 8 - 65km thick

Mantle

• Forms half of the earth (biggest section)
• Made of heavy rock
• 2900km thick
• Solid but acts as a liquid

Core (Inner and outer)

• Mainly iron
• Outer core is liquid and 2200km thick
• Inner core is solid and 1260km thick

How do we know the Earth is like this?

• Direct evidence - Rocks from volcanos, waves
• Inderict evidence - Meteors from space

How hot is the inner core? - 6000 degrees celsius. Same temperature as the surface of the sun

How many techtonic plates are there? - 14

How is Earth's magnetic field generated? - Molten metal moving within the Earth

Is the Earth's magnetic field a good thing? - Yes as it protects us from harmful sun particles

Earthquakes and volcanoes occur most frequently where plate boundaries meet.

Theory 1: Sea-level rise theory

The land hasn't moved, oceans have flooded areas of land and volcanoes have been creating new rocks, therefore changing the shape and position of the continents.

Theory 2: Convection current theory

• The core is 6000 degrees celsius
• Heated rock from the mantle rises as it is less dense
• Semi molten rock spreads out in the mantle carrying tectonic plates
• Magma cools down and sinks back down to be reheated

Theory 3: Ridge push and slab pull theory

• Ocean ridges rise high above the ocean floor and volcanic lava erupts
• As the lava cools it becomes more dense and slides down the ocean ridge
• When a denser plate sinks into the mantle under the force of gravity, it pulls the rest of the plate along behind it.