A crew drilling on the Big Island of Hawaii has
discovered magma, the molten rock material —
never before found in its natural habitat underground
— that is the central ingredient in the evolution
of planets and the lifeblood of all volcanoes.
The chance discovery far beneath the earth's surface
gives scientists an unprece-dented
opportunity to understand the important substance.
"As scientists, we've hypothesized about the nature
and behavior of magma in literally countless
studies, but before now the real thing has never been found
or been physically investigated in its
natural habitat within the earth," said Bruce Marsh, a
professor in the
Department of Earth and
Planetary Sciences at Johns Hopkins' Krieger School of
Arts and Sciences.
Magma is the subterranean form of what is known as
lava when it is ejected from the earth in
volcanoes and cools. Underground, it reaches temperatures
of more than 1,900 degrees Fahrenheit.
"Magma resides inside the earth, and lava is its
equivalent on the surface. But once magma
erupts, it begins cooling unusually quickly and it loses
any gases that it may contain, so it really is a
different animal," Marsh said. "We've never seen, until
now, the real animal in its natural habitat. And
it's not going anywhere: It's caged, so to speak."
Earth scientists are excited about the discovery not
only because it's a first but also because
the magma is a highly unusual type called dacite. Evidence
of cooled-off dacite magma is not common in
the geology of Hawaii; it is believed to be made by, in
effect, distilling basalt, the material that makes
up the floor of the ocean.
Marsh is collaborating on the discovery with William
Teplow, a consultant to Nevada-based
Ormat Technologies, the company that discovered the magma
during drilling operations at its Puna
Geothermal Venture power plant.
"This gives scientists an extraordinary chance to
examine magma in its natural habitat, which is
very, very exciting," he said.
Teplow and Marsh announced the discovery on Dec. 16 at
the 2008 fall meeting of the American
Geophysical Union in San Francisco.
Marsh, nicknamed the "Magma PI," has spent his career
investigating the processes by which
magma is forced from the bowels of the planet to the
surface and creates the geologic features —
continents, mountains, valleys — among which we live.
He does much of his fieldwork in an area quite
different from Hawaii: Antarctica. In 2005, a glacial
valley there, in the Olympus Range just south of
Mount Hercules, was named Marsh Cirque in his honor.
Workers at Ormat, one of the world's largest
geothermal producers, discovered the magma in
October 2005, when they hit a chamber of the magma about a
mile and a half down while drilling an
injection well. The substance quickly rose up about 20 feet
into the drill hole before becoming
glasslike as it cooled. Ormat workers redrilled the area
several times, with the same result.
It quickly became apparent that the magma was the
highly unusual dacite, Marsh said.
"No dacite lava or rocks have ever been found on the
Big Island of Hawaii, though some have
hypothesized that basalt can transform into dacite through
a form of distillation through
crystallization," he said.
After discovering the magma, Ormat installed a
permanent seismic- and ground-monitoring
network to provide early warning of any impending volcanic
activity for the power plant and
surrounding community.
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