Quickly cooling rock, often extrusive lava that comes from volcanoes or fissures in the earth's surface has small crystals and may be quite smooth, such as the volcanic obsidian rock.
(often extrusive lava; comes; from volcanoes or fissures in the earth's surface) (Quickly cooling rock; has; small crystals) (Quickly cooling rock; may be; quite smooth, such as the volcanic obsidian rock)
often extrusive lava Quickly cooling rock Quickly cooling rock
comes has may be
from volcanoes or fissures in the earth's surface
small crystals
quite smooth, such as the volcanic obsidian rock