Modeling Lava Flows

A grand challenge of lava flow modeling is to incorporate changing rheology and channel dynamics into quantitative models; current lava flow models are unable to successfully accommodate lava flow breakouts or dynamic changes in eruptive parameters (e.g. changes in effusion rate). While some lava flow models are able to forecast time-independent topographically controlled branching, no computational programs are currently able to model rheologically controlled flow breakouts or overflows. I am interested in using analogue models to close this gap. Using velocity measurements as a proxy for viscosity, we can gain insight into how the rheologic properties of lava evolve over time. Doing so at a manageable scale in high spatio-temporal resolution will allow for the step-wise quantification of how channels and networks grow and evolve as a function of vent dynamics, which can then be mathematically modeled. These models are necessary to create the ”rules” upon which computational codes are built.

Radar Applications for Volcanology

I am interested in using ground-based radar as a tool to monitor active lava flows. Ground based radar can create rapid sequences of digital elevation models (<5 minutes between each scan); this technology allows for the quantification of real time changes in morphology and lava flow velocity, which are important variables for lava flow models. I am also interested in using this technique to monitor deformation associated with explosive volcanism. The instrument can be used to create high-resolution DEMs in steep terrain (sub-cm scale, depending on conditions). The rapidly aquired DEMs provide a useful time series for monitoring changing ground conditions that may encourage lahar formation or rockfalls.

Communicating Hazards

Improvments on how model uncertainty is communicated are needed to incorporate the increasing complexity of forecasting tools into the way we illustrate hazards. New visualization methods will be required to present the full range of scenarios. Simple web-based hazard maps have proven very successful in disseminating information during the June 2018 eruption of Fuego, Guatemala. I would like to use the results of probabilistic modeling in the development of a new interactive mapping framework. The increasingly digital landscape of the future necessitates this type of approach.

Determining where activity will occur is one of the most important elements of assessing hazards and determining the subsequent risk. Spatial density estimation for volcanic vent distribution is used as a proxy for processes occurring at depth that control magma flux in a given region. By going straight from surface to source, we ignore the important role that crustal heterogeneities and tectonic setting play in vent distribution at a local scale. By creating a more accurate picture of the subsurface through ground penetrating radar, magnetic, and gravity based measurements, appropriate adjustments that account for the role of geology can be applied to spatial density estimates to make them more accurate. By combining these methods with tools from geomorphology (TCN and OSL dating techniques), we can better understand the evolution of these landscapes through time. These efforts will reduce uncertainty for subsequent modelling that relies on vent density estimation as a critical variable (i.e., tephra dispersion and lava flow inundation).

Ground Penetrating Radar (GPR) Surveying

GPR uses a variety of signals (50-800 MHz) to image near-surface stratigraphy. Colleagues and I have used GPR to survey the tephra blankets of cinder cones in distributed volcanic fields, colluvial wedges of faults, near-vent stratigraphy of rhyolitic domes, buried lava flow margins, and to identify ice deposits buried by tephra.

Terrestrial Radar Interferometry (TRI)

TRI is a ground-based scanning radar that measures the amplitude and phase of a backscattered microwave signal (1.74 cm λ). It can be used to measure velocities of deforming objects over short timescales (minutes between scans) and can create a time series of digital elevation models (DEMs) due to the offset of the two receiving antennae. Colleagues and I have used GPR to create high resolution DEMs and track deformation during periods of volcanic unrest.

Morphology and Elevation Modeling

High resolution elevation datasets are useful for studying the complexities of different landscape features, for processing other geophysical data, and for hazard modeling. Colleagues and I have integrated Structure-from-Motion (SfM) DEMs with satellite and ground-based radar DEMs to create high resolution models for volcanic hazard assessments. We have also used lidar to study dike and sill thicknesses in distributed volcanic fields, as well as the complexity of deposits from explosive volcanic eruptions.

Magnetic Surveying

Magnetic surveys measure the intensity of the magnetic field, which is sensitive to different magnetized deposits in the sub-surface. Colleagues and I have conducted magnetic surveys to locate buried volcanic features in sedimentary basins.

Gravity Surveying

Gravity surveys measure changes in the gravitational field at the surface and used to infer the density of materials in the sub-surface. Colleagues and I have conducted microgravity surveys to detect basin structures in the American west and to map extinct rift zones in Hawai'i.

Age Determination Sampling

Optically stimulated luminescence (OSL) dating determines the time elapsed since a sediment sample was last exposed to daylight. Cosmic rays generate terrestrial cosmogenic nuclides (TCNs) in Earth’s atmosphere and surface that are produced at a known rate and can be used to date a variety of materials and processes. Colleagues and I have used both of these techniques to date alluvial fan surfaces to determine fault slip rates in southern California.

Mapping and Stratigraphy

Integrating geologic studies with geophysical surveys is a crucial step for the application of these techniques. I have receieved extensive training in field mapping and stratigraphy in a wide range of geologic settings. I have also helped train hundreds of USF students in these techniques through my participation with our summer Field School.

Social Surveying

Quantifying geologic hazards becomes societally relevant when we view these phenomena in their relation to populations and infrastructure. Social science surveying techniques are an important method for capturing public perception of risk and hazard. I have helped disseminate surveys associated with disaster risk perception. I have also helped colleagues create and analyze surveys on evaluating engagement in technology based approaches to accessible geoscience field learning and satisfaction with geoscience training.