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The earth is not simply one big ball of rock like you might imagine!  The planet, and the layer of gas round it, is alive in a geological sense.  Here we’ll peel back the layers of the Earth, one by one.


Inner Core – The earth has a solid inner core of made mostly of iron and nickel.  Although the inner core is intensely hot (5430 °C, about the same as the surface of the sun!), it is also under extreme pressure and is therefore unable to melt.

Outer Core – The outer core has less weight on top of it and therefore is liquid or molten, melted iron and nickel.  Because of movements of the liquid metal of the outer core, the earth generates its own magnetic field, which changes shape and position over time!

Mantle – Above the core is the mantle, which is made of rock that is less dense than iron and nickel but still much heavier than normal surface rocks.  The mantle, which represents over 60% of the earth’s mass, is heated by the core enough that it is semi-solid and able to move and slide around.  The upper mantle is made up of the asthenosphere (80-200 km depth from the surface, part of the mantle that is weak and fluid) and part of the lithosphere above that (the hardened rocks of the upper mantle and the crust which forms all of the tectonic plates of the earth).


Crust – Surface rocks on the earth are made of silicon and oxygen (lighter elements) rather than iron or nickel (heavy elements).  The crust is heavier and denser under the oceans (oceanic crust) and lighter and thicker where it forms continental crust.

Atmosphere – Light elements such as oxygen, hydrogen, nitrogen, carbon, and helium, are just barely held by earth’s gravity, resulting in a 100+ km thick layer of gas around the planet we call the atmosphere.

Did you know these interesting facts about the layers of the Earth?

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