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SUMMARY
Earth, water, air and fire
t»y
Sveinbjörn Björnsson
Raunvísindastofnun Háskólans,
Dunhaga 3, Reykjavík
Intense electrical activity, lightning and
corona discharge often accompany phrea-
tic eruptions. Studies of these phenomena
during the Surtsey eruption led to the con-
clusion that the electrical activity results
from charge generation when water is
splashed on hot lava. The contact of water
with magma in craters causes phreatic
explosions. The contact of water with
intrusions which occurs under pressurized
conditions is generally not as violent, but
that process appears to be of fundamental
importance for efficient heat extraction
from hot rocks.
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