Fire and IceAsh and roughly thirty-story-tall lava fountains shoot from a half-mile-long (0.8-kilometer-long) rupture in the icy cap of southern Iceland's Eyjafjallajokull (pronounced AY-uh-full-ay-ho-kul) volcano early Sunday.Because volcanic ash can cripple jet engines, flights were not allowed in Icelandic airspace Sunday. As of Monday, air travel was gradually returning to normal, the Associated Press reported.

The geology of Iceland, though, is anything but normal. The volcanic island lies just south of the Arctic Circle atop the Mid-Atlantic Ridge, where two tectonic plates are forever pulling apart.

Magma from deep inside Earth rushes upward, filling the gaps and fueling Iceland's volcanic eruptions, which occur about once every five years.

(Read more about Iceland's volcanoes.)

Photograph by Ragnar Axelsson, AP