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 left) 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 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."