THE HOT ZONE
UNDER HAWAII
Since the 1970s, geologists have theorized that the Hawaiian Islands formed
from magma generated by a hot, rising
deep-mantle formation known as a plume.
The theory was verified in 2009 when
Cecily Wolfe, a University of Hawaii seismologist and a principal investigator of
the PLUME (Plume-Lithosphere Undersea
Melt Experiment) project, captured the
deep plume in a 3-D worm’s-eye view
(top) of the Hawaiian Islands (outlined in
yellow). “We mapped the differences
in temperature in the mantle and found
that this cylindrical shape had slower
seismic-wave speeds and was thus hotter
than the background mantle,” Wolfe
says. “We found ourselves looking at the
hot, upwelling plume that created the
Hawaiian Islands.” As the plume moves
surfaceward, it begins to partially melt,
finally emerging as lava in volcanoes
such as Kilauea, which features multiple
craters. Three thermal images (left) show
a series of Kilauea eruptions earlier this
year. Getting a clear picture of the plume
was no easy task. The project required a
dense, high-resolution network of seismometers surrounding the islands. So
Wolfe and the PLUME team deployed an
array of 70 retrievable seismometers on
the ocean floor, which no major research
group had ever done before. “These
ocean-floor seismometers are one of the
best ways to access the earth under the
oceans, and we need more of them,” she
says. “A lot of interesting things are happening beneath the ocean floor that we
don’t understand. It’s a big unknown.”
