406. Wall et al. (2020) Mantle sources interpreted from mafic volcanoes adjacent to the andesitic Goat Rocks Volcanic Complex, Southern Washington Cascades
     In the Southern Washington Cascades (SWC), broadly distributed mafic volcanoes provide information about the mantle compositions and conditions that underlie the arc. Basalts and basaltic andesites erupted on the periphery of the Goat Rocks volcanic complex, a long-lived, recently extinct andesitic center between Mt. Adams and Mt. Rainier, between about 3 Ma and 200 ka. Vent areas include Devils Washbasin, Hogback Mountain, and the Walupt Lake area. The most primitive lavas from each of these suites are calc-alkaline basalts, with an array of trace element and radiogenic isotope compositions that point to repeated tapping of multiple mantle sources. The Devils Washbasin volcano, one of the oldest mafic centers, erupted basalts distinct from others in the Goat Rocks area and from the SWC as a whole: high in Ca at given Mg, depleted in HFSE and HREE, and containing the most refractory spinel (Cr# 0.5-0.6), but isotopically similar to other Goat Rocks area basalts. Broadly, basalts from the periphery of the Goat Rocks complex fall within two groups: 1) more LILE-enriched, higher Ba/Nb, more fractionated HREE, and more radiogenic ⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd (including Devils Washbasin); and 2) less LILE-enriched, lower Ba/Nb, less fractionated HREE, and less radiogenic ⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd. Notably, lavas from both groups erupted in close spatial and temporal proximity, e.g. at Hogback Mountain and Walupt Lake. Our preliminary interpretation is that the basaltic melts are derived from repeated tapping of both a deeper, more subduction-influenced source (Group 1, with a larger degree of flux melting yielding the unique compositions of Devils Washbasin) and a shallower source with a weaker subduction component (Group 2). Isotopically, the Goat Rocks area basalts are intermediate between Mt. Adams CAB (closer to Group 1) and Mt. Adams IPB (closer to Group 2), and along with basalts from other SWC vents, form an array that is slightly oblique to the High Cascades and subparallel to the Adams Array in Pb-isotopes (Mullen et al., 2017). We infer that the HIMU-like mantle component that contributes to some Mt. Adams basalts is also distributed further north and west beneath the SWC, including the Goat Rocks area, where its contribution is diluted by a greater subduction component.
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