Most volcanism on Earth occurs in the oceans, but only about 10% of eruptions witnessed each year are submarine. This lack of observation means that there are significant gaps in our understanding of the style and impacts of submarine volcanism.

To close this gap, we use satellite remote sensing observations to observe and monitor eruptive events when submarine plumes reach or breach the ocean surface.  In some cases, this has meant the application of remote sensing techniques that are novel in the volcanic setting. So far, we have found that pumice rafts and atmospheric plumes can form at the same time, that the 2022 Hunga eruption produced a double umbrella cloud, and that the 2020 eruption of Nishinoshima triggered chlorophyll blooms in the ocean. 

(with Ralf Bennartz – Vanderbilt, Tushar Mittal – Penn State, Martin Jutzelter - University of Tasmania) 

How do pyroclasts cool and saturation with water? How do pyroclasts get to the ocean surface?

Submarine eruptions are difficult to observe and many questions remain about the dynamics of explosive submarine eruptions. For example, the processes that control the dispersal of pyroclasts underwater are poorly understood but are important for interpreting deposits and forecasting hazards. During my PhD I used experiments to quantify how pyroclasts cool and saturate in water and found that cooling, rather than permeability, controls the saturation of porous clasts ( Fauria and Manga, 2018, JVGR). Because the traditional paradigm is that permeable pathways control clast saturation, this result changes our view of, and models for, pumice saturation. 

Why does pumice float and why does pumice sink?

Cold pumice is known to float on water for months to years, yet theoretical models predict that pumice should sink within hours to weeks. To address this paradox, I worked with summer student Zihan Wei to test the idea that pumice floats because of gas trapping, the isolation of gas by water within pore throats such that the gas becomes disconnected from the atmosphere and unable to escape. We found, using X-ray microtomography experiments, that pumice does trap gas. We then proposed that pumice eventually sinks because of outward gas diffusion. Our work on pumice floatation has been published here. A news release is available here.

What mechanisms sort pumice into "floaters" and "sinkers" during submarine eruptions?

The largest submarine explosive eruption in the last century occurred at Havre Volcano, Kermadec Arc in July 2012. In April 2015 I participated in a Mapping, Exploration, and Sampling at Havre (MESH) research expedition to sample the Havre eruption products. A fundamental question about the Havre eruption remains: why did most of the volcanic material enter the pumice raft while a smaller fraction of pumice remained on the seafloor?

Using x-ray computed microtomography, and with SMART intern Christina Lin, I found that pumice is sorted into floaters and sinkers as a function of its ability to ingest water versus trap gas.  Small differences in internal texture lead to different amounts of water ingestion, which in turn determines if a clast will float or sinnk. 

Pyroclastic density currents (PDCs) are turbulent mixtures of rock and gas that propagate because they are denser than air. PDCs are hot, fast-moving, can travel across water and surmount barriers hundreds of meters high.  I use laboratory experiments and numerical models to study how topography and small-scale processes affect the distance these flows travel.

How do dilute PDCs entrain particles? How does particle entrainment affect large-scale dynamics?

In collaboration with Michael Manga and Michael Chamberlain, I conducted laboratory experiments to quantify particle entrainment due to particle "splash," the ejection of particles due to impact by a projectile. We found that the number of ejected particles scales with the velocity squared of the impactor and depth of crater generated by the impactor. We introduced particle entrainment into a new 1-D model of a dilute pyroclastic density current and found that particle entrainment can increase the runout distance of PDCs by an order of magnitude. The results from this work are available here.

How does 3-dimensional topography affect dilute PDC dynamics?

I am working with Michael Manga and Ben Andrews (Smithsonian) to explore dilute pyroclastic density current (PDC) dynamics with scaled laboratory experiments. The laboratory facilities at the Smithsonian allow us to look inside dilute density currents and determine how internal flow structures relate to large scale dynamics. I am specifically examining how topographic barriers affect dilute PDC runout distance and liftoff dynamics.