481. Fountain et al. (2023) Inventory of glaciers and perennial snowfields of the conterminous USA
     This report summarizes an updated inventory of glaciers and perennial snowfields of the conterminous United States. The inventory is based on interpretation of mostly aerial imagery provided by the National Agricultural Imagery Program, US Department of Agriculture, with some satellite imagery in places where aerial imagery was not suitable. The inventory includes all perennial snow and ice features ≥ 0.01 km². Due to aerial survey schedules and seasonal snow cover, imageries acquired over a number of years were required. The earliest date is 2013 and the latest is 2020, but more than 73% of the outlines were acquired from 2015 imagery. The inventory is compiled as shapefiles within a geographic information system that includes feature classification, area, and location. The inventory identified 1331 (366.52 ± 14.34 km²) glaciers, 1176 (31.01 ± 9.30 km²) perennial snowfields, and 35 (3.57 km² ± no uncertainty) buried-ice features. The data including both the shapefiles and tabulated results are publicly available at https://doi.org/10.15760/geology-data.03 (Fountain and Glenn, 2022).
517. Knuth (2024) Reconstructing topographic change from historical aerial images with photogrammetry and geostatistics
     Precisely measuring the Earth’s changing surface on decadal to centennial time scales is critical for many science and engineering applications, yet long-term records of quantitative landscape change are often temporally and geographically sparse. Archives of scanned historical aerial photographs provide an opportunity to augment these records and capture the historical state of the Earth’s surface at high resolution. However, historical images remain underutilized for quantitative analysis in Earth system science due to limitations of the input datasets and methodologies. In the first chapter of this dissertation, I developed an automated method to photogrammetrically reconstruct high-resolution digital elevation models (DEMs) from historical aerial photographs, with a particular focus on glacierized mountain ranges in the Western United States. Processing historical photographs at scale is challenging because images can be distorted due to film degradation and scanning artifacts, camera positions are often inaccurate or unknown, and the photographs were often collected with limited stereo overlap or inadequate stereo geometry. The method developed in this chapter addresses these challenges and is accompanied by publicly-released software that facilitates automated image standardization, block detection, multi-temporal camera model optimization, and robust DEM coregistration to high (e.g. 1 m) and low (e.g. 30 m) resolution reference terrain. In the second chapter, I designed a temporal Gaussian Process regression framework to interpolate spatially and temporally continuous surface elevation estimates from the DEMs produced in the first chapter. DEMs generated from stereo photogrammetry often lack data in areas where there are insufficient match points between images to confidently triangulate surface elevations. Data voids are problematic for glaciological analysis because a continuous estimate of the surface elevation change across the entire glacier is required to distinguish a change in mass from a kinematic redistribution of ice. The framework leverages the per-pixel temporal surface elevation covariance to predict an elevation estimate at any time step. Furthermore, the software that executes this framework is memory-efficient, user-friendly, and open-source, which enables processing at full resolution on any machine and thereby democratizes the methodology for the community. In my final chapter, I produced 70 years (∼1950 – 2020) of continuous topographic measurements and identified multiple periods of glacier advance, retreat, and stability. Mountain glaciers are perennial sources of freshwater that shape the natural landscape and provide important ecosystem services, such as aquatic stream habitat for keystone fish species and potential energy for hydropower generation. Over the past century, many glaciers in Western North America have lost mass and steadily retreated in response to long-term climate forcing. Some glaciers, especially those on stratovolcanoes with high-altitude accumulation areas and steep elevation gradients, present decadal climate-driven advances and kinematic movement on shorter (interannual) timescales. These changes can lead to significant sediment transport and devastating outburst floods that damage downstream infrastructure. To evaluate the method developed in the second chapter of this dissertation, I focused my analysis on three well-studied glaciers in the Pacific Northwest of the United States – South Cascade Glacier in the Cascade Range, Nisqually Glacier at Mount Rainier, and Easton Glacier at Mount Baker. The DEMs generated by this analysis characterize multiple periods of glacier advance, retreat, and stability at these sites, which can provide useful constraints for geophysical glacier model calibration. These long-term time series of high spatial and temporal resolution estimates produced by the methods developed in this dissertation can help constrain projections of future glacier mass change under different climate forcing and mitigate impacts on downstream water resources, infrastructure, and geohazard risk.
516. Thelen et al. (2024) Monitoring lahars
     Lahars, or debris flows that originate from a volcano (Pierson and Scott, 1985; Pierson, 1995), are among the most destructive, far-reaching, and persistent hazards on stratovolcanoes. Lahars may be triggered by syneruptive rapid melting of snow and ice, lake breakouts, or heavy rains in conjunction with large eruptive columns. Alternatively, lahars can follow eruptions, when clastic deposits are mobilized by heavy rainfall or lake breakouts, occurring sporadically for years to decades after large eruptions. Some lahars can travel many tens of kilometers in river drainages stemming from volcanoes, as during the 1980 eruption of Mount St. Helens (Washington) (for example, Janda and others, 1981), recent eruptions of Redoubt Volcano (Alaska) (fig. H1; Dorava and Meyer, 1994; Waythomas and others, 2013), and the 1991 eruption of Mount Pinatubo (Philippines) (Major and others, 1996; Pierson and others, 1996). Large lahars are less likely in the absence of eruptive activity, but still possible. The Electron Mudflow at Mount Rainier (approximately A.D. 1500), Wash., is an example of a potential noneruptive lahar, likely initiated by a spontaneous collapse of weak rock, that reached the Puget Lowland after it flowed dozens of kilometers without a recognized eruptive trigger (Sisson and Vallance, 2009). The extreme hazard posed by lahars was demonstrated tragically by the 1985 Nevado del Ruiz (Colombia) catastrophe that claimed the lives of more than 20,000 people (Naranjo and others, 1986). The potential to provide warnings of minutes to hours in advance of lahar arrival in a populated area (for example, Voight, 1990) is a strong reason to provide special monitoring attention to the hazard. Populated river valleys are located downstream from many very high threat and high threat volcanoes, and these areas could be affected by lahars (for example, Hoblitt and others, 1998). The volume and mobility of lahars are two characteristics that can influence the extent of downstream effects (for example, George and others, 2022). The flows that reach the farthest downstream are mobile and voluminous. Additionally, entrainment of material as a lahar travels downstream may increase the volume, and a lahar that starts small may grow to a destructive size under certain conditions. Increasingly, stratovolcanoes host recreational enthusiasts who could be affected by relatively localized geologic hazards, such as rainfall-induced debris flows, glacial outburst floods, rockfalls, and avalanches. These types of events can be common on many volcanoes, occurring seasonally in the case of debris flows and several times per year in the case of avalanches and rockfalls (for example, Allstadt and others, 2018). Many very high threat stratovolcanoes, especially within the contiguous United States, have low eruption frequencies (less than once per century), such that monitoring networks could be used more often for detection and characterization of small surface flows than for identification of volcanic unrest. Such information can be used to validate avalanche forecasts, inform rescue efforts, or notify other agencies of potentially damaged infrastructure (for example, roads, powerlines, or trails). Note that although many of these smaller surface flows create seismic and infrasound waves, the signals are typically highly distorted by the complex volcanic topography and geology. In general, the smaller the flow, the weaker the geophysical signals that it generates, and thus a denser geophysical network is required to study smaller flows (for example, Allstadt and others, 2018). Lahar detection may not be an appropriate or necessary monitoring capability for all volcanoes. Some very high threat volcanoes, like Kīlauea and Mauna Loa, have no lahar hazards currently, and thus no detection, tracking, and characterization capabilities for lahars are needed. At other very high threat volcanoes, such as Pavlof Volcano, Alaska, lahars might be common but pose minimal threat because the volcano is so remote. Ideally, the local observatory would understand the combination of hazard and risk associated with surface flows and assign monitoring and detection capabilities appropriately. Several volcano monitoring techniques (for example, Real-Time Seismic Amplitude Measurement [RSAM], amplitude-based locations, and infrasound array processing) can be adapted to also detect, characterize, and track debris flows, lahars, and other surface flows, so instrumentation installed for detecting volcanic unrest and eruptions can have multiple purposes. The utility of instrumentation for the purpose of monitoring unrest and lahars further justifies the importance and utility of a dense network of monitoring stations, even if the volcano remains quiescent.
515. Iezzi et al. (2024) Debris-flow monitoring on volcanoes via a novel usage of a laser rangefinder
     Mount Rainier has had at least 11 large lahars over the last 6,000 years, including one occurring without evidence of eruptive activity. This prompted the creation of a lahar detection system that uses a combination of seismic, infrasound, and tripwires. We test a laser rangefinder placed on a river channel bank for detecting and confirming mass movements flowing past a station as an alternative to the physical tripwires. After testing the device at an experimental debris-flow flume, the laser rangefinder successfully captured a small debris flow on Mount Rainier in 2023, confirming its effectiveness as a lahar detection and monitoring tool. Over the 2-month deployment at Mount Rainier, we find that spurious recordings in the laser rangefinder data (noise) tend to correlate with high humidity, and that periods of noise do not correlate with increased co-located seismic amplitude. Therefore, the impact of the noise on future alarms can be mitigated by coupling a laser rangefinder alarm with that of independent datasets.
514. Seitzinger et al. (2024) Adaptive management in the National Park Service: How Mount Rainier has grown and responded to imminent geomorphic threats
     The Imminent Threats Program at Mount Rainier National Park (MORA) is a novel addition to the typical structure of the National Park Service’s (NPS) Natural and Cultural Resources (NCR) divisions, operating as a branch of the distinguished Geology program. The landscape of MORA is characterized by steep, mountainous terrain; the very nature of the braided, glacier-fed rivers that cascade through this terrain is to change shape and structure constantly as sediment transport conditions vary. Such dynamic geomorphic surface processes pose complicated conditions for maintaining access throughout the park, affecting the integrity and longevity of park infrastructure, such as roadways, bridges, and trails. Recurrent damage to infrastructure proves that traditional maintenance and engineering techniques utilized for repairs do not work in the local environment. The need of a focused geomorphic risk group to address such inertia became identified in the early 2000’s and exists now formally as the Imminent Threats Program. The Imminent Threats technicians conduct scientific monitoring within the park to collect relevant observations of surface processes. This local knowledge is supported by additional literature review and is then used by the technicians to advise and implement holistic engineering designs fit to exist within rather than dominate the environment. The technicians also aim to influence the cultural perception of change and response to infrastructure damage within the agency workplace through their presence at interdisciplinary policy meetings, and also broader society through educational outreach. The long-running success of the projects they’re involved in encourages the Imminent Threats Program to continue to grow and influence the use of adaptive management techniques while responding to reparative needs in the park, ultimately creating improved, effective, and holistic change in resource management at MORA.
513. Todd and Jimenez (2024) Time-lapse monitoring of a small mountain glacier to capture debris flow activity
     South Tahoma Glacier is a 2 km² glacier in Mount Rainier National Park, WA that has produced 31 known debris flows since 1967, more than any other glacier on Mount Rainier. These geologic hazards threaten infrastructure and human lives along Tahoma Creek, downstream from the glacier terminus. The timing of these events and previous research suggests that debris flows from South Tahoma Glacier are most likely triggered by glacial outburst floods, which result when subglacial water storage increases due to (a) increased melt from a period of high temperatures, or (b) late summer or fall precipitation events. We installed a time lapse camera after a series of destructive debris flows in August 2015, and have monitored the glacier terminus from July - September, 2016 - 2023; we will reinstall a time lapse camera in summer 2024. We combine time lapse imagery with meteorological data, high resolution satellite imagery, and digital elevation models to investigate the relationship between recent debris flows and changes to the glacier terminus and proglacial meltwater channels. Our findings will document precursors to and impacts of debris flows from South Tahoma Glacier.

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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