70. Watters et al. (2000) Rock mass strength assessment and significance to edifice stability, Mount Rainier and Mount Hood, Cascade Range Volcanoes
    Catastrophic edifice and sector failure occur commonly on stratovolcanoes worldwide and in some cases leave telltale horseshoe-shaped calderas. Many of these failures are now recognised as having resulted from large-scale landsliding. These slides often transform into debris avalanches and lahars that can devastate populations downstream of the volcano. Research on these phenomena has been directed mainly at understanding avalanche mechanics and travel distances and related socioeconomic impacts. Few investigations have examined volcanic avalanche source characteristics. The focus of this paper is to 1) describe a methodology for obtaining rock strengths that control initial failure and 2) report results of rock mass strength testing from Mount Rainier and Mount Hood. Rock mass and shear strength for fresh and hydrothermally altered rocks were obtained by 1) utilizing rock strength and structural information obtained from field studies and 2) applying rock mechanics techniques common in mining and civil engineering to the edifice region. Rock mass and intact rock strength differences greatly in excess of one order of magnitude were obtained when comparing strength behavior of fresh and completely altered volcanic rock. The recognition and determination of marked strength differences existing on the volcano edifice and flank, when combined with detailed geologic mapping, can be used to quantify volcano stability assessment and improve hazard mitigation efforts.
536. Koepfli et al. (2025) Discovering spatial variability of critical zone processes at Mount Rainier using DAS
     Mount Rainier (4392 m a.s.l.), an active stratovolcano located ~95 km south-east of Seattle, WA, USA, poses hazards due to its steep glaciated slopes and highly porous volcanic surface. The combination of snowmelt, rainfall, and unstable surface materials frequently triggers debris flows and lahars, threatening downstream communities. At the same time, Mount Rainier’s glaciers play a crucial hydrological role, storing water that sustains rivers and therefore agriculture across the heavily populated lowlands during dry summer months. To better understand the shallow subsurface (critical zone) and its connection to the surface, we collected data using Distributed Acoustic Sensing (DAS) along a ~40 km fiber-optic cable that spans over ~1000 m elevation and crosses diverse lithologies. We analyze ambient seismic noise by using auto- and cross-correlations to image and monitor near subsurface conditions and compare our results with data from nearby weather stations, river gauges, and soil pits. We identify various coherent fiber sections and link the frequency content of seismic noise sources to local hydrological settings. We also find an increased signal-to-noise ratio for specific lithologies. Observed seismic velocity changes (dv/v) align with nearby ground moisture measurements but vary along the fiber. To explain these spatial variations, we investigate hydrological processes that connect surface conditions and subsurface responses
535. Kenyon (2025) Behind the curtain: Characterizing the Nisqually Watershed of MORA as a means to explore the use of non-contact data sources in mountain hydrology
     Impacts from a changing climate are affecting the hydrology, geomorphology, and overall variability of rivers around the world. Upland water especially prone to these effects. Mountainous rivers are experiencing significant shifts in precipitation patterns and the storage of snow and ice in source areas, resulting in stark changes to hydrologic variability, sediment transport, and fluvial morphodynamics. Most hydrology methods have been developed for use in rivers with a slope of <0.001 m/m, and the advancement of knowledge relevant to steeper rivers with has followed slowly in comparison. This research aims to address gaps in mountain hydrology associated with the measurement of discharge and bedload sediment transport in mountain rivers with a slope ≥0.02 m/m, seeking means to improve our ability to observe hydrologic trends and morphodynamics. Containing widely distributed low-resilience infrastructure, significant increases to precipitation intensities, and glacial recession rates greater than 0.1 m/day, the Nisqually River within Mount Rainier National Park (MORA) exemplifies a nexus of modern land management issues driven by climate stressors of the Pacific Northwest. With this study we seek to further characterize observable surface processes in the Nisqually watershed within MORA, and begin considering new methods and frameworks enabling reliable monitoring of steep mountain rivers. We consider the use of seismic, infrasound, and video analysis data as non-contact methods to measure discharge and sediment transport in steep mountain rivers. The primary non-contact data series can then be supported by remote LiDAR products and Sentinel-1 data to assess changes in the source areas and their potential impacts on observable behaviors. Initial data shows signals in the seismic/infrasound that seem to correlate to both water flow and bedload transport. We hypothesize there will be observable correlations with topography and snowmelt timing seen though remote sensing analysis, but also anticipate site-to-site variability based on substrate and local morphology
534. Conner et al. (2025) Characterizing surges from a debris flow induced by a glacial outburst flood at Mount Rainier, USA
     On 15 August 2023, a small debris flow occurred in Tahoma Creek on the southwest side of Mt. Rainier National Park, Washington, USA. The debris flow originated from an outburst flood from the South Tahoma Glacier. Multiple instruments installed in the Tahoma Creek drainage recorded evidence of the debris flow, including nodal and broadband seismometers, infrasound sensors, a laser rangefinder located about 3.4 km downstream of the glacier, and a timelapse camera that captured images of the glacier terminus. In particular, nodal seismometers with a sampling rate of 500 Hz were deployed roughly every 350 m along approximately 2 km of the stream. After initiation of the debris flow, we find evidence in the seismic data of at least three debris flow surges due to either additional small outbursts from the glacier or the debris flow separating into multiple surge fronts caused by wave development from flow instability. Though the arrivals of the surge fronts are often obscured by higher-frequency signals contributed by the full debris flow, we find that the surges can be tracked as they travel downstream. From the seismic data, we are able to approximate where and when the surges merged or separated from the main flow and estimate the flow velocity of each surge front. As the fronts of debris flows generally contain the largest and most damaging materials in the flow, each surge front increases the hazard associated with an event. The dense instrumentation in the Tahoma Creek drainage allows for an in-depth analysis of the evolution of debris flow surges, providing information on how similar debris flows may behave in the future and contributing to the overall understanding of how debris flows evolve over time.
533. Beason et al. (2025) Revitalizing an honor society journal: Outreach strategies for broadening undergraduate and graduate-level participation in geosciences
     Peer-reviewed publication opportunities are a vital component of professional development for undergraduate and graduate students in the geosciences. The Compass: Earth Science Journal of Sigma Gamma Epsilon, the official publication of Sigma Gamma Epsilon (the national Earth science honor society founded in 1915), has long served as a platform for student-authored research and early-career scholarship. First issued in May 1920, The Compass originally focused on chapter news and society updates, but began regularly publishing research articles in the mid-1930s. From 1982 to 1989, volumes consistently included 4–5 research articles per issue—totaling 127 scholarly contributions across seven volumes. Despite this legacy and the continued support of a national editor, submission volume has declined in recent years. The once-vibrant quarterly journal, now published digitally and featuring DOIs to enhance accessibility and citation, increasingly struggles to attract enough undergraduate and graduate research articles to fill each issue. Recent revitalization efforts aim to re-engage students and broaden participation across the geoscience community. These include the formation of a student advisory group, expanded presence at national scientific meetings, and targeted outreach through social media and campus chapters. This presentation will explore both the structural and cultural challenges of sustaining a professional-quality journal within a student-centered society, and highlight ongoing interdisciplinary strategies to promote inclusion, build awareness, and strengthen contributions. By expanding access to credible publication opportunities, we aim to support a more inclusive geoscience community and empower the next generation of science communicators.
532. Biegel et al. (2025) Seismic characteristics of the transition from debris flow to hyperconcentrated flow, Tahoma Creek, Washington
     Hyperconcentrated flows and debris flows are two types of high-discharge, highly sedimented flow events. These types of flow can be differentiated by metrics such as the amount of suspended sediment by volume, the maximum size of suspended particles within the flow column, and the critical yield strength of the flow. While there are significant differences in behavior, debris flows and hyperconcentrated flows exist on a continuum, making the transition between them not always clear. In August 2023, a debris flow occurred in Tahoma Creek in Mount Rainier National Park in Washington, USA, due to a glacial outburst coinciding with elevated streamflow from the South Tahoma Glacier. This debris flow occurred contemporaneously with a nodal geophone deployment along Tahoma Creek that allowed for close monitoring of the debris flow’s movement through the drainage system. Seismic signals recorded at stations along Tahoma Creek show evidence of the transition from debris flow to hyperconcentrated flow approximately 4.5 km downstream from the glacial source. The waveform characteristics of this transition include the loss of low-frequency energy below 10 Hz, the loss of an abrupt debris flow snout arrival within the main body signal of the flow, and a change in length, shape, and energy distribution within the main body of the signal. This transition from debris flow to hyperconcentrated flow coincides with a gradual flattening of the Tahoma Creek drainage slope and a decrease in the velocity of the debris flow as it moves down the channel. Therefore, the location of this transition in flow state is consistent with the physical system. Identifying this transition in flow state is crucial for assessing the potential hazard posed by debris flows to downstream communities, enabling better forecasts of when such events may lead to heightened hazard or to less impactful flow conditions.

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The U.S. Geological Survey Cascades Volcano Observatory and the University of Washington Pacific Northwest Seismic Network continue to monitor Washington and Oregon volcanoes closely and will issue additional notifications as warranted.

Website Resources

For images, graphics, and general information on Cascade Range volcanoes: https://www.usgs.gov/observatories/cvo
For seismic information on Oregon and Washington volcanoes: http://www.pnsn.org/volcanoes
For information on USGS volcano alert levels and notifications: https://www.usgs.gov/programs/VHP/volcano-notifications-deliver-situational-information

Jon Major, Scientist-in-Charge, Cascades Volcano Observatory, jjmajor@usgs.gov

General inquiries: vhpweb@usgs.gov