74. Frank (1995) Surficial extent and conceptual model of hydrothermal system at Mount Rainier, Washington
    A once massive hydrothermal system was disgorged from the summit of Mount Rainier in a highly destructive manner about 5000 years ago. Today, hydrothermal processes are depositing clayey alteration products that have the potential to reset the stage for similar events in the future. Areas of active hydrothermal alteration occur in three representative settings: (1) An extensive area (greater than 12,000 m²) of heated ground and slightly acidic boiling-point fumaroles at 76–82 °C at East and West Craters on the volcano's summit, where alteration products include smectite, halloysite and disordered kaolinite, cristobalite, tridymite, opal, alunite, gibbsite, and calcite. (2) A small area (less than 500 m²) of heated ground and sub-boiling-point fumaroles at 55–60 °C on the upper flank at Disappointment Cleaver with smectite alteration and chalcedony, tridymite, and opal-A encrustations. Similar areas probably occur at Willis Wall, Sunset Amphitheater, and the South Tahoma and Kautz headwalls. (3) Sulfate- and carbon dioxide-enriched thermal springs at 9–24 °C on the lower flank of the volcano in valley walls beside the Winthrop and Paradise Glaciers, where calcite, opal-A, and gypsum are being deposited. In addition, chloride- and carbon dioxide-enriched thermal springs issue from thin sediments that overlie Tertiary rocks at, or somewhat beyond, the base of the volcanic edifice in valley bottoms of the Nisqually and Ohanapecosh Rivers. Maximum spring temperatures of 19–25 °C and 38–50 °C, respectively, and extensive travertine deposits have developed in these more distant localities. The heat flow, distribution of thermal activity, and nature of alteration minerals and fluids suggest a conceptual model of a narrow, central hydrothermal system within Mount Rainier, with steam-heated snowmelt at the summit craters and localized leakage of steam-heated fluids within 2 km of the summit. The lateral extent of the hydrothermal system is marked by discharge of neutral sulfate-enriched thermal water from the lower flank of the cone. Simulations of geochemical mass transfer suggest that the thermal springs may be derived from an acid sulfate-chloride parent fluid which has been neutralized by reaction with andesite and highly diluted with shallow groundwater. The model may accomodate some of the thermal springs beyond the base of the edifice. Present heat flow from Mount Rainier is substantial relative to other Cascade Range volcanoes and does not appear to have diminished since at least the late 19th century. Evidence of older hydrothermal processes found in Holocene lithic tephra and debris avalanches record activity more extensive but similar in chemical composition to that of today.
545. Zahir (2024) An analysis of the names for Mount Rainier
     Over the years, there have been frequent attempts to rename Mount Rainier to its Indigenous name by both Native and non-Native parties (Carson, 2010; Changing the Name of Mount Rainier?, n.d.; Herbert Hoover Petition Signature Photo, 1926; Wickersham & Tacoma Academy Of Science, 1893). Through these endeavors, it has become apparent that Mount Rainier has a variety of Native names and words associated with it written in various ways that have an assortment of meanings. The result is often a lack of clarity as to what the original, Indigenous name is for Mount Rainier, and how it should be written. In this article I will present the various names and words associated with Mount Rainier and their written forms. I will then present etymological (grammar) and diachronic (historical evolution) analyses for these names. I will then discuss metaphorical meanings that have attached to these words that reflect the First People’s cultural narratives and world view of Mount Rainier.
544. Zawol and Kenyon (2026) Behind the curtain: Developing methods and toolkits supporting practical assessment of discharge and bedload of the Nisqually River within Mount Rainier National Park
     Impacts from a changing climate continue to drive changes in the hydrology, geomorphology, and inherent variability of the world's rivers. Upland watersheds with strongly coupled fluvial/hillslope dynamics are especially vulnerable to these effects, leaving mountainous watersheds in a precarious position. Classic methods for hydrologic monitoring are almost exclusively developed for rivers with slopes of <0.001 m/m, leaving steep mountain rivers comparatively unstudied, and slow to advance by comparison. This work seeks to continue efforts from the Mount Rainier National Park (MORA) Imminent Threats Program to address research gaps pertaining to the continuous measurement of discharge and sediment transport in mountain rivers with a slope ≥0.02 m/m, furthering our understanding of impacts to morphodynamic processes advancing into downstream communities. Containing widely distributed low-resilience infrastructure, significant increases to precipitation intensities, and glacial recession rates greater than 0.1 m/day, the Nisqually River of MORA exemplifies the 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 consider new frameworks enabling reliable monitoring of steep mountain rivers. Here, we continue the efforts to refine the use of seismic analysis focused on pristine mountain rivers by creating tools to package analyses, and testing combinations of field practices for calibrating model frameworks. We combine visualization and data selection tools to aid large data management of our repository (>10TB), targeting analysis for time periods of interest. We also attempt to use experimental schema of active-source calibration testing for stations within a remote monitoring network to determine Green's function parameters, moving from relative monitoring toward quantifying discharge and bedload. If successful, MORA will finally begin collecting a record of river discharge after 127 years of management.
543. Wood and Peters (2026) Influence of modeling assumptions on pedestrian evacuation success for non-eruptive lahar hazards at Mount Rainier, Washington
     Previous efforts to characterize lahar threats posed to communities downstream of volcanoes have focused primarily on delineating hazard zones that lack information on lahar-arrival times and exposure estimates that implicitly treat threats to be the same regardless of distance from the volcano. Estimated lahar-arrival times, travel times for individuals to leave hazard zones, and possible evacuation delays related to event identification, warning dissemination, and evacuee behavior are important, but often overlooked, aspects of understanding the societal threats posed by lahars. These temporal considerations are important for unexpected lahars that could occur due to slope failure in the absence of precursory volcanic unrest or eruption. This case study examines the role of time in lahar evacuations by quantifying population exposure and evacuation potential for non-eruptive lahar hazards associated with Mount Rainier, Washington. Lahars could directly affect tens of thousands of residents and employees, thousands of students at primary and secondary schools, and hundreds of individuals at long-term residential care facilities. Geospatial path-distance modeling quantified evacuation potential for 736 scenarios that represent combinations of lahar sources, evacuation destinations, pedestrian travel speeds, and a range of departure-delay assumptions. Depending on location, some communities may have substantial loss of life in tens of minutes after lahar initiation, whereas other communities may be managing large-scale evacuations over several hours. Estimates of evacuation success based on a range of scenarios provide individuals in hazard zones and risk-reduction agencies with insights on how their actions may increase or decrease the number of people that survive future lahars.
542. Raup et al. (2025) Tracking extinct glaciers in GLIMS
     Global Land Ice Measurements from Space (GLIMS), an initiative to build and distribute a database of global glacier data, has recently begun to track glaciers that have recently disappeared. GLIMS provides a definition of “extinct” glaciers for our community, and the final determination of extinction is left to local experts. There are currently 181 glaciers in the GLIMS Glacier Database that are marked as “extinct”, though we recognize that there have been many more reported in the literature. GLIMS welcomes more submissions to make the list more complete.
541. Carlson et al. (2026) Disappearing glaciers of the Oregon Cascades, USA
     The Oregon Cascades had 35 named glaciers on seven volcanoes in the 1980s, with 34 of those glaciers remaining by 2000. Here, we document the glaciers that fall into the Global Glacier Casualty List categories based on five years of field observations of these 34 glaciers. Five glaciers have disappeared, four have almost disappeared and eight are critically endangered. Thus, half of the Oregon Cascades named glaciers have disappeared, almost disappeared, or reached critically endangered status in the 21st century. Between 1980 and 2024, the May–October ablation season of the Oregon Cascades region warmed at ∼0.3°C per decade, with a 2020–24 mean temperature ∼1.7°C warmer than the 1975–84 mean. In contrast, there was no significant trend in November–April accumulation season precipitation. Given the significant rise in melt-season temperature, we attribute ongoing glacier disappearance in the Oregon Cascades to the warming climate.

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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