Partial collapse of lava delta triggers littoral
and bubble bursts.
A partial collapse of a delta's leading edge may significantly
fracture the solidified rock
around the active lava tubes, which allows seawater to seep into
the tube system.
When seawater and lava mix within the confines of a lava tube, pressure
may build to cause explosions that blast a hole through the roof
of the tube. Two types of steam-driven explosions may be generated
in such a 'confined' environment; littoral lava fountains and bubble
Littoral lava fountains
view of littora lava fountain on an active lava bench.
of a littoral lava fountain and lava tube beneath.
Spectacular and rare, this type of lava-seawater explosion produces
fountains of molten
lava and steam that reach heights of more than 100 m. The explosions
of molten spatter,
bombs, and smaller tephra fragments quickly build a circular cone
on the subsided lava delta, sometimes in a matter of minutes. Originating
from deeper within the subsided delta and closer
to the shoreline than bubble bursts, littoral lava fountains are
much more energetic
Bubble bursts are characterised by sporadic bursts of molten, dome-shaped
emanating from a circular rupture in the roof of a tube a few meters
inland from the shoreline. Individual bubbles can reach diameters
of 10 m in less than 2 seconds before they burst.
The bubble fragments continue on their radial trajectories for up
to 10 m before falling to the ground. At the end of a burst, a pool
of lava that remains in the roof of the lava tube gradually drains
away. These bursts are frequently accompanied by a loud 'boom' that
the entire delta.