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Transcript
Layers of the Earth OR The World is Like an Onion What we already know: • Two thirds of the earth is covered in water – NOT a layer • The parts not covered in water are called continents What you need to know: • Under the oceans and seas is the earth’s surface • The continents are also earth’s surface What this means: • The surface of the earth is the first layer • It is called the CRUST The Crust • The part of the crust that is under water is called OCEANIC CRUST • The part of the crust that is above sea level is CONTINENTAL CRUST More Crust • The thinnest portion of the crust is below the sea floor • 1500 meters (5000 feet) thick. All that crust fits in this skinny line crust Crust – sort of • The crust isn’t like a nut shell • More like a melon rind Crust and More • The crust and the very top portion mantle together form the LITHOSPHERE • The lithosphere is broken up into plates The Mantle • The second layer of the earth is the MANTLE • It’s the thickest layer of the earth • The top of the mantle is called the ASTHENOSPHERE • The crustal plates move around on top of the ASTHENOSPHERE Mantle Makings • The mantle is a bit like pudding –sort of solid, NOT liquid • Mantle is hot close to the center of the earth • Cooler out by the crust • The inside is 2500c hotter than the outside Moving Mantle • Because of the temperature difference within the mantle, the “pudding” moves • Hotter mantle rises toward the surface of the earth • Cool mantle moves toward the center Mantle Current crust MOHO boundary Lithospheric plate Mantle Convection • The continuous rising and falling of the mantle material is called the CONVECTION CURRENT • It is what causes the plates of the earth to move Outer Core • Really hot, VERY THICK, liquid • MOLTEN nickel, and iron • Inside of the outer core is 5,000 C Inner Core • Under a lot of pressure • So much that it is solid even though it is hotter than any other part of the earth How do we KNOW? • Direct evidence – From rock samples – Holes drilled 12 km deep • Indirect evidence – From seismic waves
