Tephra cloud generated by a large methane explosionjon Mauna Loa Volcano, Hawai`i

Photograph by J.P. Lockwood on March 31, 1984

Sketch of methane explosion in front of lava flow

Sketch by J. Johnson, 1998

M size="+2">ethane explosion

Sudden explosions of methane gas occur frequently near the edges of active lava flows. Methane gas is generated when vegetation is covered and heated by molten lava. The explosive gas travels beneath the ground through cracks and fills abandoned lava tubes for long distances around the margins of the flow. Methane gas explosions have occurred at least 100 m from the leading edge of a flow, blasting rocks and debris in all directions.

Top photo:

A dark tephra cloud rises from a large methane gas explosion in front of a slow-moving `a`a flow on Mauna Loa Volcano, Hawai`i.

Bottom sketch:

Illustration showing methane gas explosion occurring above an old empty lava tube. Cracks, fractures, and tubes in older flows beneath an active lava flow (red) serve to an explosion.