This
animation shows an interpretation of the sequence of events during the
drainback phase of a submarine volcanic eruption. The movie shows how
the rhythmic formation of vapor cavities and lava crusts form the thin,
closely spaced, horizontal "lava shelves" on the sides of
a lava pillars. The view is a cross-section through a lava flow, including
one side of a lava pillar (the hollow interior of the pillaris along
the left edge). Red is molten lava, black is solid lava crust, dark
blue is cold seawater, and light blue is hot vaporized seawater.
A description
of the sequence of events in the animation:
(1)
The movie starts after the flow is fully inflated. The lava flow has
a solid upper crust and a molten interior. The lava pillar is a hollow
pipe connecting the upper and lower crusts of the flow, allowing seawater
trapped beneath the flow to escape upwards.
(2)
As lava drainback begins, small cavities form under the upper lava crust,
and seawater is immediately syringed into these cavities through the
crust above. When the seawater encounters the molten lava a hot vapor
phase forms, allowing residual lava to drip down from the underside
of the upper crust.
(3)
The upper crust eventually fails where it is unsupported from below,
condensing the vapor and exposing the molten lava to cold seawater.
A new crust starts to form on the subsiding lava which attaches to the
side of the pillar.
(4)
As drainback continues the new lava crust becomes stranded and a new
vapor cavity forms, this time only near the pillar because the crust
stays in contact with the lava surface away from the pillar.
(5)
The perched crust also eventually fails creating a lava shelf with quenched
lava drips on its underside. This process repeats over and over until
drainback ends.
