If you could shrink Earth to the scale of an egg, the rock crust beneath you would be resting on a shell 1/1000th the thickness of an eggshell.

Earth is made up of three nested spheres. The center is called the core and it is a body of hot iron and nickel. A less dense, and much larger middle sphere is called the mantle, which is made of materials rich in iron, magnesium, and calcium. Last is a thin layer of lighter rocks called the crust.

Tectonics is the study of Earth’s crustal make-up and the forces that produce changes in it. Plate tectonics is the theory that Earth’s lithosphere (the outermost layer including all of the crust and the upper portion of the mantle) is split into approximately a dozen plates that float on the mantle. These plates rift into pieces to form new ocean basins and converge back together to form mountains and continents.

Since much of the interior of Earth is hot and under great pressure, it transfers much of its internal heat by convection. Inside Earth, irregular convection cells with the mantle transfer heat from the core to the surface. This process is the driving powerhouse behind heat transfer and plate tectonics.

Valley Of Fire Interpretive Sign

Ted: Now what?

Bill: I dunno.

Philosophize with him!

Ted: All we are . . . is dust in the wind, dude.

Bill: Dust. Wind. Dude.

So Crates: Yes, yes!

Like sands of the hourglass, so are the days of our lives!

Phhhheeeeewww, huh-hah hah haaaaaa!

Bill: Let’s get outta here, dude.