Tephra-jet explosion at leading edge of an active lava delta, Kīlauea

Explosive interaction between lava and seawater blasts a tephra jet consisting of steam, hot water, black tephra, and molten fragments into the air. Such explosions are typically directed toward the sea, but many explosions also send a shower of lava more than 10 to 20 m (33 to 66 ft) inland. Tehpra jets are the most common type of lava-seawater explosion, and typically occur when an open stream of lava is subjected to intense wave action.