"Scroll Down through History" displays the layers of rock exposed within the Grand Canyon and shows when in earth's history they formed. The region where the Grand Canyon now lies begins to shift ...

The next layer is the mantle. Many people think of this as lava, but it's actually rock. The rock is so hot, however, that it flows under pressure, like road tar. This creates very slow-moving ...

The principle of superposition states that in an undeformed sequence of sedimentary rocks, each layer of rock is older than the one above it and younger than the one below it (Figures 1 and 2).

What Was Happening on Earth at This Time The Precambrian is the earliest of the geologic ages, which are marked by different layers of sedimentary rock. Laid down over millions of years ...

undisturbed volcanic rock 3,850 million years old lies atop sedimentary rock. Within this deeper (and older) layer are minerals that contain telltale signs of past biological activity: carbon ...