Here's Something I Know Something About

From NeMO


Our Earth is a warm planet sailing through cold space. Much of the rocky interior (the mantle) of our planet is hot enough to flow, like a candy bar kept too long in one's pocket. The surface of the Earth, however, is chilled by the cold of space, and so the familiar rocks of the Earth's surface are hard and brittle. The cold outer layer of our planet, which holds together as a rigid shell, is not made of one solid piece. Instead this shell is broken into many separate pieces, or tectonic plates, that slide around atop the mobile interior.

From the NOAA web site