Volcanic eruptions are major hazards that can cause significant socio-economic effects on local populations and short-term changes to the climate that have a global impact. Many eruptions are fed by a single conduit that brings magma to the surface repeatedly over time producing major volcanic edifices associated with volcanic arcs around the world. In contrast, volcanic fields are composed of tens to hundreds of volcanic vents that are distributed over areas of 100 to 100,000 km2. These vents typically only produce a single eruption before becoming inactive and the locations of subsequent eruptions can be unpredictable and at significant distances from the previous events. Furthermore, the eruption styles within these volcanic fields can vary between non-explosive lava flows to violently explosive events that eject volcanic ash and gases tens of kilometers into the atmosphere. The San Francisco Volcanic Field (SFVF) in Northern Arizona exhibits these classic characteristics of a volcanic field and includes one of the best documented examples of an explosive eruption within these settings at Sunset Crater northeast of Flagstaff, AZ. The distribution of volcanic vents in the SFVF and why significant variability exists in the eruption styles of the volcanic field remain poorly understood. This is not only the case for the SFVF, but for every volcanic field on Earth, making it difficult to understand potential hazards these systems represent to local populations. This project seeks to better understand this system by combining seismological and eruption modeling approaches. Hundreds of instruments used for measuring ground motion (seismometers) will be installed throughout the SFVF in order to detect signals from local earthquakes. This seismological component of the project will be complemented by the development of computer models that simulate volcanic eruptions. In addition to exploring the general conditions necessary for producing non-explosive and explosive eruptions in volcanic fields, this component of the project will use the details of magma distribution beneath Sunset Crater derived from the seismological work, to constrain the specific conditions that led to this eruption. This will be the first project of its kind to produce a detailed image of the magmatic system beneath an entire volcanic field and directly use these constraints to improve eruption modeling. The work will improve hazard assessment for local populations (e.g., Flagstaff, AZ), as well as for population centers near other volcanic fields around the world (e.g., Auckland, New Zealand). Students from Chandler-Gilbert Community College in Arizona will participate in the research for this project and will be recruited to come to the University of Arizona following completion of their 2-year degrees. Teaching modules related to volcanic hazards will also be produced from this project and distributed to the broader academic community. The San Francisco Volcanic Field (SFVF) covers an area approximately 5,000 km2 in northern Arizona and includes nearly 600 basaltic vents interspersed with a few, large-volume intermediate to silicic volcanic centers. Over the past ~5-6 Myr, the locus of volcanism at the SFVF has migrated eastward at a rate of 1-3 cm/yr with the 1085 CE eruption that produced Sunset Crater being the youngest in this volcanic field. Though most of the volcanic vents within the SFVF exhibit landforms common to the effusive eruption styles of distributed volcanic fields, the Sunset Crater eruption was violently explosive and significantly affected the indigenous population living in the region at the time. Key to improving our understanding of the hazards of the SFVF is better constraining the conditions that led to the sub-Plinian style eruption at Sunset Crater which did not affect nearby volcanic vents. Existing studies have indicated that a mid-crustal magma storage zone played a key role in the Sunset Crater eruption, however, currently our understanding is limited regarding how the properties of this storage zone (e.g., size, depth, melt fraction, volatile content) influenced the eruption. Details of the crustal magma storage system that have resulted in differing volcanic compositions (mafic vs. felsic) within the SFVF are also unknown. By integrating seismic imaging and eruption modeling, this project lays out a holistic approach to better understand the subsurface magmatic plumbing system and processes that drive volcanic activity within the SFVF. Specific components of this project will include (1) detailed characterization of seismicity and the development of high-resolution 3D seismic velocity models of the crust beneath the SFVF to image current and past magmatic systems associated with this volcanic field, (2) the development of coupled magma chamber pressurization and multiphase magma ascent models to determine the conditions necessary to drive effusive to explosive basaltic eruption styles, and (3) combining constraints from seismic imaging work on the volumes and depths of crustal magma reservoirs with these state-of-the-art eruption models to better understand the subsurface processes that drove the violently explosive Sunset Crater eruption. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.