They're found 5,000 to 6,000 feet down below us. The minerals of igneous rocks crystallize from molten liquid. He throws them a curve. Ice forms by cooling from a liquid to a solid state. This formed from a frothy lava that had a lot of gas in it, so it's very light.
Granite is the next sample.
The size of crystals tells you how fast the molten material cooled. Slower cooling forms larger grains, like these in granite. Apparently, there was a lot of water in the magma, which made it quite fluid and allowed huge crystals to grow. Later, the chamber in which the rock was forming probably cracked open, letting the fluid escape. Then the magma cooled quickly, forming the fine-grained crystals you see surrounding the large ones.