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Our transcription: Geophysicists have developed a remarkably clear picture of Earth's interior. At the very center of the Earth, we have a solid inner core which is frozen iron. It's about the size of the moon. It's a crystalline ball just floating at the center of the earth. Outside of that is the molten outer core. This is liquid iron, very low viscosity, and as I mentioned, the inner core is just floating inside this molten iron ball. Then, as we get to about half the radius of the Earth, we enter the solid mantle. This is a silicate rock. Most of the Earth is made out of mantle. About 70 percent of the Earth is the mantle. This is inaccessible except by seismic waves although once in a while a piece of the mantle gets shoved up on top of the crust, and we can look at it. Then, the part of the Earth that everybody's familiar with is the crust, and that's where we live on. That's where we get our resources. That's what we mine, but it's only a very thin scum on top of the mantle.
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