3 How THICK are the layers? (entire Earth is ~ 8000 miles wide)Crust: oceanic crust miles thickcontinental crust miles thickMantle: about1700 miles thick(2/3 of Earth’s mass)Outer core: about1400 miles thickInner core: about1500 miles thick
4 How HOT are the layers?Crust: 0oC at surface 400oC where it contacts mantleMantle: ~500oC to~3700oC deeper downOuter core: ~4000oCInner core: ~7000oC(hotter than the surfaceof the sun!!)
5 What are the layers made of? Crust: RockMantle: Dense rockOuter core:Liquid metal (iron) !!Inner core:Solid metal(mostly iron)
6 Of course, it’s not quite that simple: The “lithosphere” is the crust + part of the upper mantle.It is made of rock and is brittle. The “plates” of the earth’scrust make up the lithosphere.Below the lithosphereis a softer layer calledthe “asthenosphere”.In the asthenosphere,The rock is near it’smelting point, andflows very slowly, kindof like asphalt or tar.
7 Why the partly melted asthenosphere?? This graph shows why there is a layer of soft, partially melted rock (the ASTHENOSPHERE) in the top part of the mantle of the earth.From 100 to 200 km ( miles) below the surface, the temperatures are above the melting point of the rock - even at the very high pressure at this depth.MELTINGPOINT OFROCK(yellow)ACTUALTEMP(green)This layer - the ASTHENOSPHERE - is what the plates of the crust“float on” and explains why they can move around.
8 Finally – a very cool map showing thickness of earth’s crust (in km) Continental crustis thick.Oceanic crustis thinner