The Earths structure & tectonic plates

What are the layers of earth?

Crust, mantle, outer core, inner core.

Describe the crust

0 - 60km thick and is solid rock that we live on. Either oceanic or continental crust.

Describe the mantle

Thickest layer, approx. 2900km. It is made up of semi-molten rock

Describe the outer core

Liquid layer made up of iron and nickel.

Describe the inner core

Hottest part - 5,500*c and made up of iron and nickel.

What is the theory of continental drift?

Posed by Alfred Wegener in 1914, continental drift is the theory that all the continents were once connected (Pangaea) but had drifted apart over time.

What were his 3 pieces of evidence?

Jigsaw fit = The continents were able to fit together like a jigsaw.

Fossils = Similar fossils were found on continents separated by miles of ocean.

Rock formations = Similar rock patterns were found on various coastlines.

Rock formations = Similar rock patterns were found on various coastlines.

Why didn't scientists believe him at the time and why do they now?

Because he could not explain why it was happening, furthermore he was a trained astronomer and meteorologist not geologist. They believe him now because of evidence found in the 1950's - magnetism in the ocean floor showed that the seafloors were spreading a few centimetres each year. Also new rock was found on seafloors proving it had been recently made.

What are plate boundaries?

Plate boundaries are where plates meet, and there are 3 types: Constructive, Destructive and Conservative.

Explain what happens at a Constructive plate boundary

At a constructive plate boundary the plates move apart due to convection currents in the earths mantle. Magma rises into the space between the plates, to cool and form new 'igneous' rock. These repeats many times and volcanoes are often made.

Explain what happens at a Destructive plate boundary

Destructive plate boundaries usually involve a continental plate and an oceanic plate. This time, the plates move together and the more dense oceanic plate is forced under the continental plate. This rock melts into magma. This may cause fold mountains and a volcano if theres a build up of pressure.

Explain what happens at a Conservative plate boundary

Conservative plate boundaries are when two plates move sideways past each other, or in the same direction at different speeds. Crust is not created or destroyed here, but the friction between them can cause earthquakes.