Heat output through hydrothermal venting in this region is high, but studies suggest that a much greater amount of magma is cooled within the crust. Because little is known about the properties and extent of this magma, Heise et al. map subsurface structures within the Taupo zone. Through magnetotelluric imaging methods, which plot spatial variations in electric currents induced by natural fluctuations in Earth's magnetic field, the authors generate a map of the zone’s conductivity structure. They find a steep increase in conductivity at a depth of 10 kilometers (6 miles), corresponding to a region about three kilometers (1.9 miles) beneath the base of the seismogenic zone and eight kilometers (5 miles) above the base of the continental crust. The authors hypothesize that this increased conductivity marks the presence of molten material within the lower crust.-American Geophysical Union