|Lava fountains (10 m high) spouting from eruptive fissures during the October 1980 eruption of Krafla Volcano. (Photograph by Gudmundur E. Sigvaldason, Nordic Volcanological Institute, Reykjavik, Iceland.) http://pubs.usgs.gov/gip/dynamic/Krafla.html
Volcanic activity on the Earth occurs mainly along the junctions of the great plates of the Earth's lithosphere.
This is a USGS illustration from http://pubs.usgs.gov/gip/dynamic/fire.htm
Lutgens & Tarbuck