Our World

What went on here?
When magma erupts at the surtace in a volcanic explosion, it cools so quickly that qrains (crystals) do not form. This results in obsidian, which has a vitreous (glass-like) and compact texture, Pumice which can also result, is also vitreous, but it is more like a sponge- with many holes. The holes represent bubbles of gas that escaped from the magma as it cooled quickly.