Yellowstone National Park is indeed an electrifying place. Researchers have used observations of Earth's electromagnetic field collected at more than 100 sites surrounding the park to create a CT scan-like image of the plume of hot rock responsible for today's geysers and hot springs (main image) as well as past volcanic activity in the region. Variations in the conductivity of rock underlying the region—which conducts electricity in some places as well as seawater does (dark red, inset)—reveal zones rich in molten silicate rocks and hot briny fluids, the researchers report in a forthcoming issue of Geophysical Research Letters. The plume may stretch more than 600 kilometers westward of the Yellowstone basin, the new report suggests. In the past decade or so, several other teams of geoscientists, including one with one of the researchers making the new report, have spotted the plume using seismic waves. The electromagnetic image of the plume is broader than the one derived from seismic data but doesn't extend as deep, largely because the electromagnetic waves the study analyzed can penetrate only 300 kilometers or so of Earth's crust.
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