Lava is molten rock expelled by a volcano during an eruption. Lava fountains are volcanic phenomena in which lava is forcefully, but not explosively ejected from a volcano. Lava fountains may occur as a series of short pulses or continuous jets of lava.

Lava flows occur when low-viscosity lava is nonforcefully erupted from a volcanic vent. Lava flows can flow for miles. They have been known to destroy homes in Hawai'i.

Slowly flowing lava in Hawai'i covers a road. Park rangers are in the background moving a building to save it. Photo courtesy of USGS.

Lava fountaining at Pavlof volcano in Alaska. Photo courtesy of AVO.