The superdense center of the earth composed of two layers: a liquid outer layer and a solid inner core of metallic iron-nickel alloy.
- Interior of the Earth [More info]
- General Interest Publication on the structure of the planet Earth including the crust, the mantle, and the core with drawings to scale on the cover and a table listing the thickness of the parts.
- What on Earth is plate tectonics? [More info]
- Discussion and diagrams on plate tectonics and the structure of the Earth for beginners with link to a detailed version: This Dynamic Earth for more information.