83. Beason et al. (2014) Lessons learned from a bi-national exchange between Colombia and the United States: Real-life emergency planning and preparedness from a worst-case scenario
    On 13 November 1985, after almost a year of increased activity, Nevado del Ruiz volcano in Colombia’s Cordillera Central range of the Andes erupted violently. Pyroclastic flows swiftly melted glacial ice and snow to generate lahars (volcanic mudflows) that swept down river valleys through urban and rural areas tens of kilometers from the volcano. Despite several hours of warning and potential evacuation time, lahars caused more than 23,000 casualties, largely due to an uninformed populace and ineffective emergency protocols. Since the event, Colombian geologists, emergency planners, and elected officials have greatly improved community education and emergency evacuation systems near multiple active volcanoes and these new systems have proven highly effective during subsequent eruptions. As an opportunity to learn from the Nevado del Ruiz disaster and the subsequent planning by Colombian authorities, a ten-member delegation from Washington State representing Federal, state, and local emergency managers, planners, and scientists visited Colombia in August 2013 as part of a bi-national exchange with their Colombian counterparts. Participants viewed effects of the 1985 eruption and the Colombians’ more recent mitigation efforts. The most striking lessons learned by US participants concerned the importance of pre-designated and well publicized evacuation routes, information hubs, community involvement in all aspects of planning and preparedness, and frequent exercising of notification devices and evacuation. Subsequently, ten Colombians visited Washington State in September 2013 to learn from our efforts in volcano preparedness and mitigation. Using new knowledge about effective eruption preparations, U.S. bi-national exchange participants are expanding efforts for preparedness and mitigation in communities at risk. Some examples include: preliminary development of a statewide volcano awareness/preparedness plan in Washington, and upgraded Pierce County evacuation maps, information kiosks placed around the county; development of new Mount Rainier Volcano Hazards website (http://www.piercecountywa.org/activevolcano); local FEMA-USGS Volcano Crisis Awareness trainings and plan exercises; and almost two dozen public presentations during the 2014 Volcano Preparedness Month.
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.
540. Ghent et al. (2026) When every second counts: Parental decision-making in Mt Rainier’s lahar inundation zone
     Mount Rainier, a heavily glaciated stratovolcano in Washington State [USA], has a documented history of producing major lahars. The potential for future high-magnitude flows threatens approximately 90,000 downstream residents and has prompted one of the nation’s most extensive volcanic monitoring systems, including a specialized lahar detection network. Because portions of Rainier’s west flank are composed of hydrothermally altered, unstable rock, the region is especially vulnerable to “no-notice” lahars triggered by sudden, non-eruptive slope failure. In response, schools in at-risk zones have conducted lahar evacuation drills – now a legal requirement – for over two decades, demonstrating that on-foot evacuation is the most effective strategy for student and staff safety. Despite these efforts, many parents report an intention to retrieve their children from school during an emergency lahar evacuation, contradicting official guidance. Such actions could obstruct evacuation routes, delay emergency response, and increase personal risk, especially in areas where modeled lahar arrival times are under one hour. Parent decision-making thus presents a critical, yet understudied, variable in evacuation planning and is considered integral to the success of city-wide evacuations. Here we present the ongoing work from focus groups held with local parents to explore motivations behind their intentions. Topics of discussion within the focus groups include parents’ general understanding of lahar hazards, their intended actions, their confidence in school evacuation plans, and underlying factors in their decision-making. These insights can support more effective communication and preparedness strategies by emergency managers and school officials, while also contributing to broader discussions about protective action decision-making in rapid-onset hazards beyond volcanic settings.
539. Conner et al. (2026) Quantifying seismic properties of a river channel at Mount Rainier for use in debris flow monitoring and analysis
     Theoretical models that relate debris flow properties to their seismic signature suggest seismic methods may be used to remotely characterize properties of these events. However, the complexity of debris flow sources and poorly constrained material properties in near‐surface environments limit our ability to determine important attributes of debris flows, such as volume and particle size distribution, from seismic records alone. In this study, we explore the sensitivity of debris flow seismic signals to subsurface seismic characteristics using an established debris flow seismicity model and subsurface properties derived from active‐source measurements in the Tahoma Creek stream channel at Mount Rainier, United States. Using refraction and multichannel analysis of surface waves, we estimate 1D primary and secondary wave velocity profiles to a depth of 11 m and calculate the frequency‐varying phase velocity (⁠v_c) and Rayleigh‐wave quality factor (⁠Q_R⁠) for frequencies between 9 and 50 Hz. We find that the Tahoma Creek stream channel has low ⁠v_c, varying with frequency between 226 and 434 m/s, and is highly attenuating, with Q_R⁠ estimated below 13.3 at all analyzed frequencies. We model the seismic signal of a hypothetical debris flow in Tahoma Creek using our measured values and compare the results against the same model but varying v_c and ⁠Q_R over a range of frequency‐independent, single values commonly used in the literature when measurements are not available (⁠v_c = 250-750 m/s, ⁠Q_R = 3-33⁠). We find that the power spectral densities of the modeled debris flows vary by orders of magnitude within the subset of our test values, highlighting the benefits of measuring material properties when using modeled debris flow seismic signals for quantitative monitoring.
538. Wall et al. (2026) Origin and evolution of mafic volcanism associated with 3 m.y. of andesite production at the Goat Rocks volcanic cluster, southern Washington Cascade Range
     More than 3 m.y. of mafic volcanism near the Goat Rocks volcanic cluster in the southern Washington Cascade Range, USA, lends insight into the evolution of basalts and the subarc mantle at a long-lived, major arc volcanic locus. We contribute field observations, 40Ar/39Ar dates, paleomagnetic directions, and bulk rock and mineral compositions to characterize nine mafic units that erupted in association with the Goat Rocks volcanic cluster. The time frame of mafic volcanism, ca. 3.6 Ma to 60 ka, encompasses the lifespan of the central volcanic cluster (3.1 Ma to 115 ka), with a lull from ca. 2.7 Ma to 1.4 Ma. A climactic period of voluminous mafic activity and far-traveled lava flows, including construction of the Hogback Mountain shield volcano, coincided with voluminous andesite eruptions from the central volcanic cluster. The basaltic rocks in the Goat Rocks area are calc-alkaline to barely tholeiitic and have high field strength element depletion relative to large-ion lithophile elements characteristic of calc-alkaline basalts (CAB) of the Cascade volcanic arc. Unlike at neighboring andesitic volcanic centers (Mounts Adams, St. Helens, and Rainier), no other mafic end members such as high-aluminum olivine tholeiite (HAOT) or intraplate-type basalt (IPB) are present at or near the Goat Rocks volcanic cluster, although some of the calc-alkaline basalts in this study have IPB-like affinities. The Goat Rocks mafic units exhibit two main temporal trends in composition: (1) the most primitive basalts erupted earlier, compared to less primitive and more evolved compositions later, and (2) high field strength element concentrations are higher in the younger basalt units relative to the oldest two. In contrast to these temporal trends, the mafic units define two compositional groups that recur through time, a low-Sr and a high-Sr group, each with distinct trace element and Sr and Nd isotope ratios. Although radiogenic isotope ratios are generally aligned with High Cascades CAB and HAOT, some extend toward IPB of Mount Adams and Simcoe Mountains volcanic field. Olivine-dominated crystal fractionation at shallow pressure from a small range of parent magma compositions accounts for much of the variation among the basalts and basaltic andesites. A high-pressure fractionation model is plausible for only one of the youngest basalt units (basalt of Walupt Lake volcano). Mafic recharge and crustal assimilation accounts for the incompatible-element enriched composition of basaltic andesites erupted during construction of the largest andesitic centers, further supporting sustained basalt mass flux and thermal energy driving andesite genesis. We model the most primitive members of the Goat Rocks mafic units as partial melts of successively less depleted mantle in time. Variable degrees of fluxing with fluids and melts from subduction explain the distinction between high-Sr and low-Sr groups. We propose that mantle metasomatism by ancestral subduction and fluid-flux melting is heterogeneously distributed through the local subarc mantle and played a greater role in the genesis of the high-Sr basalt group. The limited range of primitive basalt types around the Goat Rocks volcanic cluster contrasts with the much greater diversity of basalts throughout the southern Washington to northern Oregon Cascade arc. On the other hand, the central volcanic cluster encompasses nearly the entire diversity observed at neighboring composite volcanoes. In the case of the Goat Rocks area at least, and perhaps attributable to the entire region, this means that the genesis of diverse intermediate magmas is independent from and does not require vastly different parental basalt compositions.

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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