450. Fordham (2022) Glacier Peak and the chocolate factory: Recurring debris flows from the eastern flank of Glacier Peak stratovolocano, North Cascades, Washington State, USA
     Alpine mass wasting events can have wide ranging impacts that extend past their headwater origins reaching down to lowland population centers. The Suiattle River, which drains the eastern flank of Glacier Peak in the North Cascades of Washington State, is a dominant contributor of suspended sediment in the region. Normalized for drainage area, the Suiattle River supplies more suspended sediment than nearly any other river in the region and more than twice as much as the White Chuck River, which drains the western flank of the volcano. Despite its known importance to the regional sediment budget, the specific geomorphic drivers of the anomalous sediment load on the Suiattle have received relatively little attention in the literature. In this study, I build on previous work to explore the magnitude, timing, triggering mechanisms, and the spatial distribution of sediment loading events in the Suiattle River Basin. My historical analysis shows that major debris flow activity initiated in the late-1930s, with a total of nine historic debris flows since then (RI = 9.3 years). One previously unreported circa late-1940s debris flow was identified from reanalysis of dendrochronology (Slaughter, 2004) and historical aerial imagery. From topographic differencing, I placed a minimum bound of ~4.9 M m3 (±0.6 M m3) on the material incised from the most recent valley filling debris flow deposits. Historical accounts suggest that major debris flows happen at the hottest times of the year in the absence of precipitation, with two eyewitness accounts of debris flows triggered by glacial outburst floods. Historical photos, remote sensing, and field measurements of terrace heights suggest that incision into historic debris flow deposits occurs soon after deposition and tapers after the first few years. To examine smaller more recent debris flows, I created a framework to automatically extract debris flow timing, duration, and magnitude from USGS turbidity and discharge data over the period 2011 to 2020. I identified 28 individual debris flow events that occurred in every year in the record. To evaluate triggering mechanisms, I calculated prior day maximum temperature anomalies for all non-debris flow days and for days when a debris flow started. Debris flow start days were shown to be statistically warmer than non-debris flow days (mean of -0.21 °C and 2.48 °C, respectively; ks test, dm = 0.314, p = 0.007). This suggests that minor debris flows are triggered by high temperatures and, like the historical major debris flows, points to glacier outburst floods as the primary initiation process. I estimate suspended sediment loads attributable to minor debris flows, anomalous sediment flushing events following debris flows, and suspended sediment loads outside of these categories. Together debris flows and flushing account for ~21% of the mean annual load on the Suiattle. At Glacier Peak, Chocolate Glacier is unique. Its high propensity for glacier outburst floods makes it the dominant source of debris flows and suspended sediment, vastly outweighing contributions from other glaciers on the mountain. The frequency and magnitude of debris flows from Chocolate Glacier bare similarities to South Tahoma Glacier at Mount Rainier. Combined, my findings show that debris flows deliver large quantities of sediment to the mainstem river at both annual and decadal timescales. This work is a step toward understanding how sediment supplied from alpine mass wasting events shapes downstream geomorphic processes. My findings have implications for how ongoing climate change may alter cascading hazards in these systems.
554. Beason and Kenyon (2026) Interpreting summit elevations on Mount Rainier: Contextualizing ice-surface change, bedrock elevation, and geodetic frameworks
     Recent work has documented measurable changes in the elevation of ice-capped summits across the western United States, including Mount Rainier. At Mount Rainier, comparisons between mid-20th century survey data and modern GNSS measurements indicate a decrease in the elevation of the highest point on the mountain, driven by long-term thinning of summit ice. Here, we examine these results within the broader glaciological and geodetic context of Mount Rainier, where more than a century of observations document sustained changes in glacier thickness, extent, and mass balance. We emphasize the importance of distinguishing between ice-surface elevation and bedrock elevation when interpreting summit measurements on glaciated volcanoes, and describe how differences in vertical datums, measurement approaches, and temporal variability influence apparent elevation change. We synthesize existing datasets to demonstrate that observed elevation differences are consistent with long-term glacier thinning and are not indicative of lowering of the underlying volcanic edifice. We further highlight how terminology and framing influence interpretation of elevation change, particularly for prominent peaks where findings may be communicated beyond academic contexts. This contribution expands on recent work by providing geodetic context, integrating long-term datasets, and offering recommendations for consistent terminology and measurement practices in studies of glaciated summits.
553. Nuth and Kaab (2011) Co-registration and bias corrections of satellite elevation data sets for quantifying glacier thickness change
     There are an increasing number of digital elevation models (DEMs) available worldwide for deriving elevation differences over time, including vertical changes on glaciers. Most of these DEMs are heavily post-processed or merged, so that physical error modelling becomes difficult and statistical error modelling is required instead. We propose a three-step methodological framework for assessing and correcting DEMs to quantify glacier elevation changes: (i) remove DEM shifts, (ii) check for elevation-dependent biases, and (iii) check for higher-order, sensor-specific biases. A simple, analytic and robust method to co-register elevation data is presented in regions where stable terrain is either plentiful (case study New Zealand) or limited (case study Svalbard). The method is demonstrated using the three global elevation data sets available to date, SRTM, ICESat and the ASTER GDEM, and with automatically generated DEMs from satellite stereo instruments of ASTER and SPOT5-HRS. After 3-D co-registration, significant biases related to elevation were found in some of the stereoscopic DEMs. Biases related to the satellite acquisition geometry (along/cross track) were detected at two frequencies in the automatically generated ASTER DEMs. The higher frequency bias seems to be related to satellite jitter, most apparent in the back-looking pass of the satellite. The origins of the more significant lower frequency bias is uncertain. ICESat-derived elevations are found to be the most consistent globally available elevation data set available so far. Before performing regional-scale glacier elevation change studies or mosaicking DEMs from multiple individual tiles (e.g. ASTER GDEM), we recommend to co-register all elevation data to ICESat as a global vertical reference system.
552. Hotaling et al. (2022) Summer dynamics of microbial diversity on a mountain glacier
     Glaciers are rapidly receding under climate change. A melting cryosphere will dramatically alter global sea levels, carbon cycling, and water resource availability. Glaciers host rich biotic communities that are dominated by microbial diversity, and this biodiversity can impact surface albedo, thereby driving a feedback loop between biodiversity and cryosphere melt. However, the microbial diversity of glacier ecosystems remains largely unknown outside of major ice sheets, particularly from a temporal perspective. Here, we characterized temporal dynamics of bacteria, eukaryotes, and algae on the Paradise Glacier, Mount Rainier, USA, over nine time points spanning the summer melt season. During our study, the glacier surface steadily darkened as seasonal snow melted and darkening agents accumulated until new snow fell in late September. From a community-wide perspective, the bacterial community remained generally constant while eukaryotes and algae exhibited temporal progression and community turnover. Patterns of individual taxonomic groups, however, were highly stochastic. We found little support for our a priori prediction that autotroph abundance would peak before heterotrophs. Notably, two different trends in snow algae emerged—an abundant early- and late-season operational taxonomic unit (OTU) with a different midsummer OTU that peaked in August. Overall, our results highlight the need for temporal sampling to clarify microbial diversity on glaciers and that caution should be exercised when interpreting results from single or few time points.
551. Kincaid (2024) Using historic glacial data and GIS to predict Mount Rainier National Park's glacial future
     Will Washington state have glaciers 100 years from now (year 2124)? Due to generally warmer weather glaciers are largely in retreat globally, including the glaciers in Washington state. In Washington state summer glacial meltwater plays a vital role in the survival of wildlife and is needed for human purposes that include recreation, power generation, drinking, agricultural, and industrial. This project looked at the most resilient glaciers in Washington state, the glaciers at Mount Rainier National Park. Historic measurements were used in an exponential growth calculation to project the amount in acres each glacier at Mount Rainer will advance or retreat over the next 100 years. The glaciers were digitized into ArcGIS Pro and then adjusted according to the calculations. The results of the project show that all the glaciers at Mount Rainier should be intact in 2124. This is of vital importance to wildlife and human populations that depend on the summer meltwater for various purposes.
550. Florea et al. (2022) Fumarole-ice dynamics in cryo-speleology on volcanic edifices—Mount Rainier, Washington, USA
     The persistent fumarole ice caves nearly circumnavigating the East Crater of Mount Rainier in the Cascade Volcanic Arc in Washington, USA, are a natural laboratory to study the dynamic equilibrium between thermal flux and glacial ice. The large circum‐crater passage connects to entrances on the crater rim by steep transverse passages, and fumarole gas convection and advection maintains the cave passage distribution and morphology. Between August 2016 and August 2017, we collected hourly data using remote sondes that include temperatures at three fumarole, cave air temperature and pressure, water temperature and depth in an in‐cave meltwater lake, and the outside temperature and snow depth at Paradise Visitors Center. Correlation and wavelet analyses of these data reveal complex associations between patterns of weather, fumarole activity, and lake level. At longer scales, fumarole temperatures behave largely independently and connected to spatial and temporal changes in volcanic heat flux and glacial melt circulation. At the scale of individual storm‐events, major snowfalls seal the cave entrances, increasing cave air temperature and pressure from fumarole output and causing rising lake levels from increased melt until entrances reopen. Repeating freeze‐thaw cycles observed in the cave monitoring data are a primary cause of crater mass‐wasting.

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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