Our Beautiful World
Explosions at the Edge of an Active Lava Delta
When lava pours into the ocean at high rates from a lava-tube entry, beautiful and spectacular explosions called tephra jets commonly occur. With temperatures higher than 1,100 degrees C, lava can instantly transform seawater into steam, causing explosions that blasts hot rocks, water, and molten lava fragments into the air. In general, the more intense the incoming waves, the more energetic the tephra jets. The incoming waves disrupt the lava exiting the tube and increases the surface area of the molten stream that is exposed to seawater by more than 10 to 20 times.
The most violent and dangerous steam-driven explosions, however, occur when the leading edge of a growing lava delta suddenly subsides or collapses into the sea. The resulting disruption of the lava tube system within the delta forces seawater to mix with lava and hot rock surrounding the tube system in a confined environment.
For people standing on the delta or its leading edge,
these sudden steam-driven
Types of Explosions
Based on observations during the growth of several lava deltas along Kilauea Volcano's southeast coast between 1992 and 1994, four general types of explosive interactions between lava and seawater have been identified;
1) Tephra jets and blasts typically occur
when part of a lava delta completely
2) Bubble bursts and littoral lava fountains
may occur when the leading edge of a delta
Since a growing delta may collapse or subside at any time and the intensity of any one type of explosion may change suddenly, a growing lava delta is hazardous and should only be viewed from behind the former sea cliffs.
Complete collapse of lava delta triggers large tephra jets and blasts
A complete collapse of a delta's leading edge will
sever lava tubes within the delta so that an