Lava flow hazards are one of the few constant themes across the wide spectrum of volcanic research in the solar system. These dynamic hazards are controlled by the location of the eruption, the topography and material properties of the land upon which the flow spreads, and the properties of the lava (e.g., volume, temperature, and rheology). Understanding the influences on eruption location and how lava flows modify the landscape are important steps to accurately forecast volcanic hazards. Three studies are presented in this dissertation that address di˙erent aspects of modeling and assessing vent opening and lava flow hazards. The first study uses hierarchical clustering to explore the distribution of activity at Craters of the Moon (COM) lava field on the eastern Snake River Plain (ESRP). Volcanism at COM is characterized by 53 mapped eruptive vents and 60+ lava flows over the last 15 ka. Temporal, spatial, and spatio-temporal clustering methods that examine different aspects of the distribution of volcanic vents are introduced. The sensitivity of temporal clustering to different criteria that capture the age range of magma generation and ascent is examined Spatial clustering is dictated by structures on the ESRP that attempt to capture the footprint of an emplacing dike. A combined spatio-temporal is the best approach to understanding the distribution of linked eruptive centers and can also provide insight into the evolution of volcanism for the region. Spatial density estimation is used to visualize the differences between these models. The goal of this work is to improve vent opening forecasting tools for use in assessing lava flow hazards. The second study presents a new probabilistic lava flow hazard assessment for the U.S. Department of Energy’s Idaho National Laboratory (INL) nuclear facility that (1) explores the way eruptions are defined and modeled, (2) stochastically samples lava flow parameters from observed values for use in MOLASSES, a lava flow simulator, (3) calculates the likelihood of a new vent opening within the boundaries of INL, (4) determines probabilities of lava flow inundation for INL through Monte Carlo simulation, and (5) couples inundation probabilities with recurrence rates to determine the annual likelihood of lava flow inundation for INL. Results show a 30% probability of partial inundation of the INL given an e˙usive eruption on the ESRP, with an annual inundation probability of 8.4×10^−5 to 1.8×10^−4. An annual probability of 6.2×10^−5 to 1.2×10^−4 is estimated for the opening of a new eruptive center within INL boundaries. The third study models thermo-mechanical erosion of a pyroclastic substrate by flow-ing lava on Volcán Momotombo, Nicaragua. It describes the unique morphology of a lava flow channel using TanDEM-X/TerraSAR-X and terrestrial radar digital elevation models. New methods for modeling paleotopography on steep-sided cones are introduced to mea-sure incision depths and document cross-channel profiles. The channel is incised ~35 m into the edifice at the summit and transitions into a constructional feature halfway down the ~1,300 m high cone. An eroded volume of ~4×10^5 m3 was calculated. It is likely that a lava flow eroded into the cone as it emplaced during an eruption in 1905. There is not suÿcient energy to thermally erode this volume, given the observed morphology of the flow. Models are tested that explore the relationship of shearing and material properties of the lava and substrate against measured erosion depths and find that thermo-mechanical erosion is the most likely mode of channel formation. Additionally, it is likely that all forms of erosion via lava flow are impacted by thermal conditions due to the relationship between temperature and substrate hardness. The evolution of these structures (their creation and subsequent infilling) plays an important role in the growth of young volcanoes and also controls future lava flows hazards, as seen by the routing of the 2015 flow into the 1905 channel.

Magmatism is a dominant process on Earth and Mars that has significantly modified and evolved the lithospheres of each planet by delivering magma to shallow depths and to the surface. Two common modes of volcanism are present on both Earth and Mars: central-vent dominated volcanism that creates large edifices from concentrating magma in chambers before eruptions and distributed volcanism that creates many smaller edifices on the surface through the independent ascent of individual magmatic dikes. In regions of distributed volcanism, clusters of volcanoes develop over thousands to millions of years. This dissertation explores the geology of distributed volcanism on Earth and Mars from shallow depths (~1 km) to the surface. On long time scales, distributed volcanism emplaces magmatic sills below the surface and feeds volcanoes at the surface. The change in spatial distribution and formation rate of volcanoes over time is used to infer the evolution of the source region of magma generation. At short time scales, the emplacement of lava flows in these fields present an urgent hazard for nearby people and infrastructure. I present software that can be used to simulate lava flow inundation and show that individual computer codes can be validated using real-world flows. On Mars, distributed volcanism occurs in the Tharsis Volcanic Province, sometimes associated with larger, central-vent shield volcanoes. Two volcanic fields in this province are mapped here. The Syria Planum field is composed three major volcanic units, two of which are clusters of 10s to >100 shield volcanoes. This area had volcanic activity that spanned 900 million years, from 3.5-2.6 Ga. The Arsia Mons Caldera field is associated with a large shield volcano. Using crater age-dating and mapping stratigraphy between lava flows, activity in this field peaked at ~150 Ma and monotonically waned until 10-90 Ma, when volcanism likely ceased.