Collaborative Research: Moving mountains: timing and emplacement of the Marysvale gravity slide complex

Volcanic fields are dynamic environments, characterized by rapidly evolving landscapes and extreme hazard potential. This research project is focused on learning and understanding the processes involved in collapse of volcanic fields and production of mega-scale landslides. The project objectives will be achieved by geologic mapping of the ancient Marysvale gravity slide complex in southwestern Utah, one of the largest such structures in the world that is made up of three individual mega-scale slides, determining the age of rocks contained in the slides, and modeling slide initiation and lateral transport to distances over 35 km to the south of their initiation sites. This research project assembles a new multi-institution, multi-disciplinary collaboration and will provide support for graduate and undergraduate students. High-resolution 3D geologic data collected during this study will be used to develop virtual field trips and field camp mapping modules. These modules will be interactive and contain outcrop models, geologic maps, and samples that will enable students and the public to learn more about volcanic hazards and mega-scale landslides. The modules will also serve a broader mission to make the Earth Sciences accessible to a broad, diverse population. During the late Oligocene to Miocene, the Marysvale volcanic field of southwestern Utah, USA, experienced three consecutive mega-scale catastrophic collapse events, collectively called the Marysvale gravity slide complex (MGSC). The stratigraphic succession, kinematic indicators, basal structures, pervasive fragmentation, and pseudotachylyte collectively suggest that emplacement of each of these slides occurred at high velocity during individual events. Outstanding questions for these landslides include (1) the conditions of the volcanic field that made it susceptible to mega-scale collapse, and (2) the factors which allowed the resulting gigantic slides to travel tens of kilometers at high velocity, driven by gravity. The MGSC provides an excellent opportunity to address these questions due to the exceptional exposure of the internal structure and basal slide planes of the slide blocks. Through a multidisciplinary approach combining geologic mapping, geochronology, rock mechanics analyses, and numerical modeling, we will evaluate the timing of slide initiation with respect to evolution of the volcanic field and major eruptive events, the role of a frictionally weak substrate on slide initiation, and the combined roles of thermal pressurization, damage, and shear localization on slide mobility and deceleration. Geological mapping and field work, combined with 40Ar/39Ar and zircon U-Pb geochronology, will provide constraints on timing, the dimensions and continuity of each slide, and the structure of the basal sliding surface. Laboratory measurements of rock properties, combined with field-based geologic parameters, will be used to constrain numerical models of both the coupled processes facilitating slide mobility and the conditions of pre-slide stability, representing an unprecedented level of geologic constraint on models of massive-scale, long runout landslides. This project is jointly funded by the Tectonics program and the Petrology & Geochemistry program in the division of Earth Sciences. 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.