When very ﬂuid lava erupts through the constricted opening of a narrow volcanic vent, expanding gas bubbles may cause it to jet, like water from a hose, in a fountain of glowing, molten rock. The earliest visible event in the eruption of a shield volcano may be a series of such fountains, called a “curtain of ﬁre,” spewing from a ﬁssure at the top of the volcano or along a rift zone. On Hawai‘i Island in 1959, lava fountained for several weeks from a pipelike vent in Kilauea Iki Crater, adjacent to the main caldera of Kilauea Volcano. The vent acted like a high-pressure nozzle, spraying lava as high as 1,900 feet and spewing cinder downwind for several miles. That height record was broken by a lava fountain on Izu-Oshima Volcano in Japan in 1986 that reached over 5,000 feet. The Galileo spacecraft has photographed lava fountains with an estimated height of one mile on Io, one of Jupiter’s moons.