512. Ruzzante and Gleeson (2024) Increasingly hot and dry summers exacerbate low flows and threaten pacific salmon habitat throughout Northwestern North America
     Excessively low stream flows in the late summer can disrupt aquatic life cycles, including those of ecologically and culturally significant species such as Pacific Salmon. Climate change is expected to drive hydrologic changes throughout northwestern North America, but the magnitude and direction of changes to low flows remain highly uncertain. Here we study 375 near-natural catchments, across rainfall-dominated, hybrid, snowmelt-dominated, and glacial regimes throughout the habitat range of Pacific Salmon from California to Alaska. Annual minimum summer discharge has decreased in most catchments; rainfall-dominated and hybrid catchments, which predominate in coastal watersheds and in the southern half of the range, have seen the most severe declines. We predict low flows using linear regression models which significantly outperform existing process-based models. We hindcast low flows back to 1900 and project changes to 2100 under four emissions scenarios. Low flows have historically been driven primarily by summer precipitation and moderately influenced by winter snow accumulation and summer temperature. However, we find that future changes will likely be driven by temperature because the magnitude of projected heating is large compared to the historical variability of temperature. Some further declines in low flows are probably inevitable in rainfall-dominated and hybrid catchments: under a low-emissions scenario, low flows will continue to decline to mid-century but then stabilize. Under a high-emissions scenario, 1-in-50-year low flows could occur almost every summer in rainfall and hybrid catchments. Bold climate action and mitigation strategies are urgently required to safeguard these habitats.
522. Pang et al. (2025) Long-lived partial melt beneath Cascade Range volcanoes
     Quantitative estimates of magma storage are fundamental to evaluating volcanic dynamics and hazards. Yet our understanding of subvolcanic magmatic plumbing systems and their variability remains limited. There is ongoing debate regarding the ephemerality of shallow magma storage and its volume relative to eruptive output, and so whether an upper-crustal magma body could be a sign of imminent eruption. Here we present seismic imaging of subvolcanic magmatic systems along the Cascade Range arc from systematically modelling the three-dimensional scattered wavefield of teleseismic body waves. This reveals compelling evidence of low-seismic-velocity bodies indicative of partial melt between 5 and 15 km depth beneath most Cascade Range volcanoes. The magma reservoirs beneath these volcanoes vary in depth, size and complexity, but upper-crustal magma bodies are widespread, irrespective of the eruptive flux or time since the last eruption of the associated volcano. This indicates that large volumes of melts can persist at shallow depth throughout eruption cycles beneath large volcanoes.
521. Obryk et al. (2025) Utility of a swath laser rangefinder for characterizing mass movement flow depth and landslide initiation
     Mass movements such as debris flows and landslides are some of the deadliest and most destructive natural hazards occurring mostly in alpine and volcanic settings. With ever-growing populations located downslope from known debris flow channels, early warning systems can help prevent loss of life. Geophysical and technological advances have improved monitoring and detection capabilities in recent years; however, they can often be cost prohibitive and resource intensive, making them less accessible to disadvantaged populations. We tested and validated a readily available and cost-effective two-dimensional swath laser rangefinder in a controlled experimental setting against two independent flow-depth lasers. The swath laser successfully recorded cross-sectional changes in flow depth from four debris flows and a water-only flood, in addition to geomorphic changes associated with landslide initiation. The results suggest that a swath laser could be integrated into systems for debris flow detection and characterization of mass movements in natural settings, thus improving the ability to monitor these hazards.
520. Gendaszek et al. (2025) Spatial stream network modeling of water temperature within the White River Basin, Mount Rainier National Park, Washington
     Water temperature is a primary control on the occurrence and distribution of fish and other ectothermic aquatic species. In the Pacific Northwest, cold-water species such as Pacific salmon (Oncorhynchus spp.) and bull trout (Salvelinus confluentus) have specific temperature requirements during different life stages that must be met to ensure the viability of their populations. Rivers draining Mount Rainier in western Washington, including the White River along its northern flank, support a number of cold-water fish populations, but the spatial distribution of water temperatures, particularly during late-summer baseflow during August and September, and the climatic, hydrologic, and physical processes regulating it are not well constrained. Spatial stream network (SSN) models, which are generalized linear models that incorporate streamwise spatial autocovariance structures, were fit to mean and 7-day average daily maximum water temperature for August and September for the White River Basin. The SSN models were calibrated using water temperature measurements collected in 2010 through 2020. The extent of the models included the White River and its tributaries upstream from its confluence with Silver Creek in Mount Rainier National Park, Washington. SSN models incorporated covariates hypothesized to represent the climatic, hydrologic, and physical processes that influence water temperature. SSN models were fit to the measured data and compared to generalized linear models that lacked spatial autocovariance structures. Statistically significant covariates within the best-fit models included the proportion of ice cover and forest cover within the basin, mean August air temperature, the proportion of consolidated geologic units, and snow-water equivalent. Statistical models that included spatial autocovariance structures had better predictive performance than those that did not. Additionally, models of mean August and September water temperature had better predictive performance than those of 7-day average daily maximum temperature in August and September. Predictions of the spatial distribution of water temperature were similar between August and September with a general warming in the downstream part of the mainstem White River compared to cooler water temperatures in the high-elevation headwater streams. The proportion of ice cover emerged as an inversely related significant covariate to both mean August and September water temperature because streams that receive glacial meltwater are colder than non-glaciated streams. Water temperatures of the upper White River increased downstream and are attributed to warming of water temperature from accumulated solar radiation and inflow of non-glaciated tributaries. Estimated water temperatures for the upper White River model are 3–4 degrees Celsius (°C) warmer for tributaries, but 1–2 °C cooler for the mainstem compared to the regional-scale model. Differences between the upper White River SSN model and the regional-scale NorWeST model are attributed to the fact that the upper White River SSN included water temperature observations specific to the upper White River, whereas water temperature observations from lower elevation streams and downstream from the Mount Rainer National Park boundary were used in the regional scale model.
519. Jimenez (2025) Degradation of Martian glacier-like forms in relation to the observed evolution of Emmons glacier on Mount Rainier, WA
     This study establishes parallels between the observed degradational evolution of debris-covered glaciers on Mount Rainier, WA and select glacier-like forms (GLFs) by studying the time-varying morphologies of the debris cover. Mount Rainier is home to 28 debris-covered valley glaciers, including Emmons Glacier which has a history of orthoimages taken from 1951 to 2023 and high-resolution Digital Elevation Model (DEM) coverage of 2008, 2021 and 2022. We can observe the degradational evolution of Emmons Glacier through orthorectified black and white imagery collected from an airborne platform and the National Agricultural Imagery Program (NAIP) colored satellite images periodically collected over the last 72 years. GLFs in the Mars mid-latitude areas are indicative of past ice flow based on visual interpretations of their overall forms and from surface textures that are similar to glaciers on Earth. On Mars, GLFs are the smaller flows by area that appear most similar to debris-covered valley glaciers on Earth. Morphological textures discernable in tonal and spatial variation display supraglacial landform evolution of debris-covered glaciers on Earth, including Emmons Glacier on Mount Rainier observable at the meter scale with DEMs. Observations of Emmons Glacier show that these textures—such as crevasses, ridges, and moraines—develop and degrade over time as ice thins and debris accumulates. These evolutionary stages provide a baseline for interpreting similar textural patterns in Martian GLFs, suggesting that these Martian features may represent advanced stages of degradation, potentially analogous to the later stages observed at Mount Rainier.
518. Crandell (1967) Potential effects of future volcanic eruptions in Mount Rainier National Park
     An evaluation of the geologic events of the last 10,000 years at Mount Rainier suggests that, if the past pattern of volcanic activity continues, a substantial steam, pumice, or lava eruption will occur on an average of once each 500-1,000 years. Furthermore, these eruptions predictably will be accompanied by destructive floods and mudflows along the floors of some valleys that head on the sides of the volcano. The purpose of this report is to describe the ways in which an impending eruption might be recognized, to discuss the effects that might be anticipated from an eruption, and to recommend ways in which potential threats to human life might be reduced or eliminated. In addition, the potential hazards at various visitor-use facilities and Park maintenance installations are discussed, and suggestions are made concerning the possible relocation of some of these facilities. The accompanying Appendix, "Procedures to follow in case of a volcanic eruption," is prepared in such a way that, if desired, it can be reproduced for distribution to Park Service personnel responsible for various installations at the Park. The information given here concerning the eruptions of the last 10,000 years is summarized from Geological Survey Bulleting 1238, "Volcanic hazards at Mount Rainier, Washington," by Dwight R. Crandell and Donal R. Mullineaux, which is now in press.

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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