1. STRUCTURE OF THE EARTH
Noadswood Science, 2011

2. Structure Of The Earth To know the structure of the Earth
Friday, April 14, 2017
Structure Of The Earth
To know the structure of the Earth

3. Earth
What is the structure of the Earth like?

4. A mantle – has the properties of a solid but it can also flow
Earth
The Earth is almost a sphere, consisting of four main layers…
Crust – relatively thin and rocky
Mantle – has the properties of a solid, but can flow very slowly
Outer core – made from liquid nickel and iron
Inner core – made from solid nickel and iron
A thin crust – km thick
A mantle – has the properties of a solid but it can also flow
A core – made of molten nickel and iron. Outer part is liquid and inner part is solid
The average density of the Earth is much higher than the crust, meaning the inner core must be very dense – solid nickel and iron

5. Earth

6. Earth
The radius of the core is just over half the radius of the Earth (the core itself consists of a solid inner core and a liquid outer core)

7. Plate Tectonics
Why does the Earth look the way it does – has it always looked this way and will it remain?

8. Plate Tectonics
Why does the Earth look the way it does – has it always looked this way and will it remain?
The Earth's crust and upper part of the mantle are broken into large pieces called tectonic plates – these are constantly moving at a few centimetres each year
Although this rate is not great, over millions of years the movement allows whole continents to shift thousands of kilometres apart – called continental drift
The plates move because of convection currents in the Earth's mantle, driven by the heat produced by the decay of radioactive elements and heat left over from the formation of the Earth

9. Plate Tectonics
Where tectonic plates meet, the Earth's crust becomes unstable as the plates push against each other, or ride under or over each other
Earthquakes and volcanic eruptions happen at the boundaries between plates, and the crust may ‘crumple’ to form mountain ranges

10. Alfred Wegener
The theory of plate tectonics and continental drift were proposed at the beginning of the last century by a German scientist, Alfred Wegener
Before his time it was believed that the planet's features, such as mountains, were caused by the crust shrinking as the Earth cooled after it was formed
It took more than 50 years for Wegener’s theory to be accepted because it was difficult to work out what the mechanism was that could make whole continents move, and it was not until the 1960s that enough evidence was discovered to support the theory fully

11. Tectonic Theory
Alfred Wegener suggested that the continents looked like they ‘fit’ together
He also noted they have similar rock patterns and fossil records – these two pieces of evidence led him to believe that there was once a single land mass, and form the tectonic theory
The massive amounts of heat generated through radioactive decay in the core power convection currents in the mantle causing the crust to move, as well as the spreading of the sea floor at plate boundaries as new crust is formed – both key discoveries and proof of Wegener’s theory

12. Evidence
Plate tectonics explained why earthquakes and volcanoes were concentrated in specific places - around the boundaries of moving plates
The match in shape between the east coast of South America and the west coast of Africa suggests both were once part of a single continent
There are similar patterns of rocks and similar fossils on both sides of the Atlantic - including the fossil remains of land animals that would have been unable to swim across an ocean

13. Plates

14. Continental Drift

15. Pangaea
Pangaea – the original super-continent is thought to have broken up in the following manner…
Earth around 200 million years ago, at the time of Pangaea
The single landmass began to crack and divide, due to the convection currents of the magma beneath
Current continental positions

16. Plate Boundaries

17. Crust
Complete the structure of the Earth worksheet…

18. Crust
The Earth’s lithosphere (crust) is split up into different sections called tectonic plates, which are moving apart from each other a few centimetres every year due to the convection currents in the mantle caused by the radioactive decay of rocks inside the core