For those who remember the classic disaster-docudrama Supervolcano (BBC-Discovery Channel 2005), the adjective “eruptible” is likely to ring a bell. Set in the near future and generally quite scientifically literate, the movie envisions volcanologists trying desperately to evaluate the near-term threat posed by the giant Yellowstone magmatic system. At the heart of their mission, and of the drama, is their quest to determine the mass of “eruptible magma” under Yellowstone: that is, how much material that is capable of erupting is down there right now? Fortunately, the scientists have at their disposal VIRGIL, a seismic tomography system that is based upon but greatly upgraded from existing systems. VIRGIL can reliably detect eruptible magma but, unfortunately, it is just coming on-line, and when they discover that there is in fact an enormous reservoir beneath them that can erupt, the scientists lack context. Given a gigantic mass of eruptible magma, what if any sort of eruption—or eruptions—is likely to occur, how soon will it begin, how long will it last, how explosive will it be, and how should scientists and the government respond? Supervolcano doesn’t turn out well, despite the heroism of the scientists. In PNAS, the search for context is at the heart of research presented by Barboni et al. (1). Geophysical techniques, as represented by VIRGIL and its less-sophisticated present-day tomographic counterparts and by magnetotelluric and gravity surveys, provide a real-time glimpse of where magma is—or may be—stored within the crust (2). Results to date are intriguing but frustrating. Surveys suggest the presence of molten material beneath a growing number of volcanoes. In fact, gigantic volumes of the crust beneath Yellowstone and the Washington Cascade volcanoes, St. Helens, Rainier, and Adams, appear to contain melt (3, 4). However, these zones are interpreted to mostly contain very small melt … [↵][1]1Email: calvin.miller{at}vanderbilt.edu. [1]: #xref-corresp-1-1