Does Volcanic Ash Fertilize The Globe? (22 Sep 2026)

Wed, 23 Sep 2026 00:30:00 GMT

Does Volcanic Ash Fertilize The Globe?

Hubert Staudigel

Scripps Institution of Oceanography at the University of California in San Diego

Volcanic soils are legendary for their fertility, and in particular volcanic ash is commonly considered as a potentially commercial use as a mineral fertilizer. The benefit of volcanic ash as a fertilizer appears obvious based on its nutrient contents but it is not clear whether, and under which circumstances this holds true. Staudigel will discuss the relationships between soil fertility and volcanic input into a soil through controlled greenhouse experiments that have shown that volcanic ash may result in a threefold increase in bioproductivity. This talk is based on a recent, freely downloadable paper published in the Journal Ecosphere (DOI: 10.1002/ecs2.70406) .

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7:00 pm presentation

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Corridor of Cataclysm -- mapping the perilous geologic journey of the Owyhee River (27 Oct 2026)

Wed, 28 Oct 2026 00:30:00 GMT

P. Kyle House, PhD

University of Arizona

Arizona Geological Survey

Over the last 2 My, the Owyhee River—aided by diverse geologic processes and events—has carved a spectacular landscape into the high-desert volcanic terrain of southeastern Oregon. River-corridor-focused geologic mapping reveals a repeating ‘triad of catastrophe’: immense lava dams that fossilize valleys, regrade canyons, and eventually breach; channel-blocking landslides that reorganize drainage and generate outburst floods; and pluvial lake outburst floods from remote sources that sweep through the corridor. Yet through each episode, the river reasserts itself, resuming incision until the next cataclysm. This catastrophic cycle is regenerative. A late Miocene, pre-river framework of volcanic and lacustrine deposits is susceptible to slope instability. As the river incises, it exposes additional unstable strata, while lava damming redirects channels into susceptible slopes and reloads the canyon with basalt flows and lacustrine deposits. In this way, lava damming reconstitutes the vulnerable stratigraphy promoting future instability.

When lava enters the corridor, momentum drives lobes upstream, where explosive contact with the river builds a prograding delta of interbedded subaerial lava, pillow lava, and hyaloclastite, a structurally weak assemblage. As the lava dam and lake grow, the canyon downstream becomes a conduit for lava that repaves and regrades the dry channel with tens of meters of basalt resulting in a steep tapered wedge of rock. The battle upstream produces the dam’s internal vulnerability; the downstream flows produce its mass. Together they construct a blockage that self-destructs. Because water fills reservoirs faster than sediment, the first phase of dam degradation is hydraulic. The dam begins consuming itself via plucking and transporting coarse monolithologic gravel we termcannibal gravels. Lowering of the crest accelerates delta advance, and once the delta reaches the declining outlet, its rich sediment load accelerates incision, while the poorly consolidated lava-delta margins serve as landslide food, rebuilding slope instability along the canyon walls. The river then resumes incision into an even narrower canyon where the triad looms. Drawing on nearly two decades of field mapping, this presentation traces and maps the Owyhee’s course through repeated impoundment, catastrophic release, and drainage reconstruction. Moreover, this remarkable record reveals how rivers persist, and landscapes evolve in the face of multiple origins of channel blockage and outburst flooding.