Inner Core: 1. Pressure and temperatures in the inner core squeeze the metal so much it is not able to move like a liquid, but is forced to vibrate in one place like a solid. 2. Temperatures reach about 9000 degrees F. 3. Pressures are so great, we would be squeezed into a marble-sized ball. 4. About 800 miles thick. Outer Core: 1. The outer core is so hot, the metals that make it up are all in a liquid state. 2. The outer core is comprised of iron (Fe) and nickel (Ni). 3. The rotation of Earth on its axis causes the outer core to spin, creating Earth's protective magnetic field. 4. About 1400 miles thick. Mantle: 1. The asthenosphere is the semi-rigid part of the middle mantle. It moves like hot asphalt. 2. The mantle is the thickest layer of the earth, at about 1800 miles thick. 3. It is composed of hot, dense rock that flows. 4. The movement of the middle mantle (the asthenosphere) is the reason the crustal plates move. 5. Convection currents in the asthenosphere are caused by very hot material in the deepest part of the mantle rising, then cooling near the top of the mantle, and then sinking againrepeating this cycle over and over. Crust: 1. The crust is the outer-most layer of the earth; the part we live on, the surface. 2. It is the thinnest layer, like the skin on an apple. 3. The crust and the upper-most solid portion of the mantle together are the lithosphere. 4. The crust is only about 3-5 miles thick under the oceans. These oceanic crustal plates are mostly made of dense basalt. 5. The crust is up to about 25 miles thick under the continents. This continental crust is mostly granite, which is less dense than basalt. 6. The crust is broken into pieces called lithospheric or tectonic plates which float on the soft, semi-rigid asthenosphere.