Monday,
March 12, 2012
6:00 - 7:30 pm
Pellissippi
State Technical Community College
10915 Hardin
Valley Road, Knoxville
J.L Goins Administration Building, Cafeteria Annex
MARCH
PRESENTATION
Subaerial
Lava Pillars: Evidence for Non-Explosive
Lava-Water Interactions in Iceland
By
Kenneth Christle
Knoxville, Tennessee
Abstract
Submarine lava
pillars are hollow pipes of solidified basaltic lava that are
interpreted to form in lobate lava flows on the deep (>2000
meter water depth) seafloor as heated water rises between
adjacent advancing lava lobes. As long as the flow of water
within the pillar interior continues, it is inferred that the
pillar conduit will remain open. If the water ceases to flow
through the conduit, the pillar may be filled in with lava.
Models suggest that submarine pillars remain standing while the
molten interior of the lava flow drains out. Features that
resemble submarine lava pillars have been observed in the
subaerial environment in Iceland near Lake Mývatn and in the
Skælingur region as part of the Younger Laxá and Laki fissure
lava flows respectively. The subaerial pillars have similar
morphologies to their submarine counterparts: they are cylinders
of basalt with central conduits that display different amounts of
infilling. I propose that these subaerial pillars formed in
lobate lava flows that advanced over wet substrates (or possibly
into shallow ponded water) and were left standing after the body
of the lava flow drained away.
There are differences between submarine and subaerial pillars.
These include pillar interiors that, in submarine pillars, are
lined with glassy lava drips and, in subaerial pillars, are
filled with small (<10 cm across), bulbous lava protrusions.
Additionally, submarine pillars have horizontal glassy shelves
covering the external walls. These shelves are interpreted to
have formed by lava quenching during drainout. In contrast,
shelves on subaerial pillars are less common and with larger
spaces between them. Along with horizontal shelves, subaerial
pillars display curled segments of lava crust that have the
appearance of peeling away from the vertical pillar wall. I infer
that these features form on the exterior walls of subaerial
pillars during drainout. Based on field observations of the
textures on subaerial pillar walls, I infer that, during lava
drainout, superheated gasses are trapped beneath a solidified
lava flow roof that keeps the outside of the pillar wall hot
while the molten lava drains out. This is similar to thermal
conditions in a partially filled lava tube.
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