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Abstract

The near-field source region for volcanic eruptions is magma. At present, evaluating the risk of imminent volcanic eruption is based almost entirely on untested interpretations of data from a variety of remote sensors, separated from the eruption source by kilometers of solid rock. There is not even consensus as to what the source is: a mush chimney with regions of melt segregation? An accumulation of mostly melt? Or at what pressure it exists: hydrostatic? least principal stress? lithostatic (ρgh)? lithostatic + ΔP? In contrast to currently dominant views, accidental (the only kind there have been) drilling encounters with magma have found only melt-rich magma, no mush. Given this dangerous state of ignorance, we need to explore the source of volcanic eruptions directly. What is the state of this material before eruption, as revealed by quenching it in situ under pressure? What do the signals of unrest recorded at the surface actually mean about processes in magma-hydrothermal systems? The Krafla Magma Testbed (KMT), Iceland, an ICDP project, seeks to answer these questions with a doublet of boreholes to magma. The first will core and permanently instrument the interval from brittle rock to magma, establishing physical, chemical, and mechanical source conditions. This borehole will become a monitoring post for the second well, where intentional perturbation of pressure and temperature of the magma and flow testing of the expected high-enthalpy fluid will be matched to signals at depth and at the surface. Obviously, there are implications for exploiting superhot geothermal energy as well.