Plate Tectonics Flashcards
Inner Core
Radius of 1200km
Is a solid, dense ball of metal
Composed of iron and nickel
Temperatures above 6000C
Outer Core
Radius of 2200km
Moves around the inner core, creating a magnetic field
Composed of iron and nickel
Temperatures 4000-5000C
Mantle
Radius of 2900km
Makes up 84% of Earth’s volume
Composed of iron, magnesium and sulphides
Top part is the solid lithosphere
Bottom part is the malleable asthenosphere where convection currents occur
Temperatures around 3000C
Oceanic Crust
Composed of basalt and gabbro
6km thick
Found under oceans
Continental crust
Composed of granite
35km thick
Found under land masses
Thicker, older and less dense
Slab pull
Occurs at a destructive boundary.
Dense, oceanic plate is subducted.
As the plate sinks into the mantle, the rest of the plate follows.
Convection currents
Hot magma rises and spreads out under the plate.
As it cools, it becomes denser and sinks.
Ridge push
Also known as Gravitational Sliding
Occurs at constructive plate boundaries
Magma rises up and solidifies, creating new plate and pushing old plate apart.
What did the Theory of Continental Drift suggest?
Suggested that all the continents were once joined together as a supercontinent.
Who proposed the Theory of Continental Drift?
Alfred Wegner
What was the single supercontinent called?
Pangea
What is the evidence that continental drift occurred?
Edges of continents fit together.
Identical fossils have been found in South America and Africa.
Tropics coal deposits found in Antarctica, North America and the UK.
Similar glacial deposits found in Antarctica, South America and India.
What did the Theory of Paleomagnetism suggest?
Suggested that the movement of the plates was caused by thermal convections in the mantle.
Who proposed the Theory of Paleomagnetism?
Alfred Holmes
What is the evidence for the Theory of Paleomagnetism?
As magma erupts from mid-ocean ridges, the magnetic material aligns itself with the Earth’s magnetic field. Some material has reversed polarity.
Alternating magnetic strips can be found along the sea floor, showing that the older the crust is away from the ridge.
