Pele Meets the Sea
Part II: Still Photographs of Active Lava
Under water lava flows
Studying moving lava flows underwater in Hawaii provides a rare
opportunity for scientists to see how quickly the lava flows are
quenched by the ocean, and how this cooling affects the appearance
of the lava. Here we see just a few of the views captured by the
University divers.
Close to the active lava, our diver finds that pillow basalts form from
relatively slow moving submarine lava flows. This slow movement allows the
overlying seawater to rapidly cool the molten lava, which causes a surface
crust to quickly form, giving the resulting rock its distinctive pillow
shape. Large numbers of gas bubbles are released from the pillow basalts
while they form. These bubbles are distinctive in that they contain
relatively high levels of explosive hydrogen gas, which is formed by the
chemical reaction of sea water with the hot lava.
The formation of pillow lava underwater is accompanied by a steady stream
of sounds. Some are the result of fracturing of the cooling crust and the
implosion of the solid pillows. Other loud explosions result from the
combustion of hydrogen trapped under the cooled outer skin of the lava
flow.
It is also fascinating to see growing hot lava flows under water. Some of
the pillows observed at Kilauea are exceptionally fluid, and form long toes
such as the one seen here that have a central crack that propagates the
growing toe of incandescent lava.
It has been generally assumed by geologists that underwater lava flows
always produce pillows. However, at Kilauea we have seen other types of
underwater flows. These are fast-moving flows, similar to the channelized
lava flows observed on shore, and are fed by tubes that open directly onto
the seafloor.
Violent hydrogen explosions and jets of hot water can frequently be seen
along the larger active underwater flows below the mouth of the lava tube.
These explosions and hot springs are the results of sea water seeping down
into the seafloor and coming in contact with buried lava tubes. The
temperature of the jets is near the boiling point of water, as indicated by
the steam they vent. The jets are also another source of hydrogen-rich
bubbles.
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[Beginning of Pele Meets the Sea]
Diving and video movie: Richard Pyle, Jane Culp,
Frank Sansone
,
Gordon Tribble, Jane Tribble, David Schideler, Kevin Kelly, John
Earle, Randall Kosaki; Digitization and HTML presentation:
Cristina Lumpkin and Pierre Flament
To see some related photos and for references to some more
information that may be of interest, please check out the link
to Frank Sansone's web page on our
Project Linkspage.
