17. Ellinger (2010) The changing glaciers of Mt. Hood, Oregon and Mt. Rainier, Washington: Implications for periglacial debris flows
    Mountain glaciers are receding worldwide with numerous consequences including changing hydrology and geomorphology. This study focuses on changes in glacier area on Mt. Hood, Oregon and Mt. Rainier, Washington where damaging debris flows have occurred in glaciated basins. Landsat imagery is used to map debris-free ice on a decadal time scale from 1987 to 2005. Debris-free glacier ice is clearly delineated using a ratio of Landsat spectral bands in the near-infrared part of the spectrum (bands 4 & 5). Landsat scenes were chosen during the months of September and October to minimize snow cover left over from the accumulation season and maximize exposure of debris-free glacial ice. SNOTEL data were also used to find the lowest snow year for each decade to minimize the potential of misclassifying remnant snow as glacial ice. Changes in debris-free ice are mapped to produce the most up-to-date rates of glacier retreat. Average glacial slopes, derived from airborne LiDAR data are used to compute slope corrected debris-free ice areas for all glaciers. A threshold value for the Landsat NDGI scenes was selected based on threshold testing on the Eliot and Reid glaciers on Mt. Hood. Contradicting earlier studies that say the glaciers on Mt. Hood are receding faster than the glaciers on Mt. Rainier, results show that from 1987 to 2005 Mt. Rainier and Mt. Hood lost similar amounts of debris-free ice extent at 14.0% and 13.9%, respectively. For both Mt. Hood and Mt. Rainier the change in slope corrected debris-free ice area was greater than that of the projected area change due to the steep slopes of both mountains. For Mt. Rainier an increase in recession rate was shown from 1992-2005 compared to 1987-1992 while on Mt. Hood the opposite is seen. On Mt. Rainier it was found that highly fragmented glaciers at lower elevations such as the Inter, Pyramid, and the Van Trump Glaciers lost the highest percent of their original 1987 ice extent and were also shown to be associated with new debris flows in 2006. On Mt. Hood none of the 2006 debris flows initiated within zones of recent glacial recession, however, all debris flows from 2006 originated from streams with a direct connection to glaciers. The Newton Clark Glacier, having lost the most coverage of debris-free ice from 1987 to 2005, is also associated with the highest number of debris-flows in its drainage since 1980. Precipitation data for both mountains show no trend but there was a statistically significant increase in summer air temperature at Mt. Hood over the period 1984-2009. This study suggests that glaciers may play a role in the location of initiation sites, of debris flows, but there is not enough evidence to argue that glacier recession is responsible for producing debris flows.
484. Gagilano et al. (2023) Capturing the onset of mountain snowmelt runoff using satellite synthetic aperture radar
     The timing of snowmelt runoff is critical for water resource applications, but its spatiotemporal evolution remains poorly understood. We present a scalable approach to map snowmelt runoff onset using Sentinel-1 synthetic aperture radar data for the past 8 years with 10 m spatial resolution and a median temporal resolution of 3.9 days. A systematic analysis of stratovolcanoes in the Western United States showed that snowmelt runoff onset is strongly dependent on elevation (r = 0.81), with a median runoff onset lapse rate of 4.9 days per 100 m of elevation gain. During the 2015 snow drought, we observed snowmelt runoff onset 25 days early relative to the 2015–2022 median. We document a median shift in snowmelt runoff onset of +2.0 days later in the year per year between 2016 and 2022. Our open-source tools can be used to create snowmelt runoff onset maps anywhere on Earth.
483. Anderson and Jaeger (2019) Coarse sediment dynamics in the White River watershed
     Changes in upstream sediment delivery or downstream base level can cause propagating geomorphic responses in alluvial river systems. Understanding if or how these changing boundary conditions propagate through a watershed is central to understanding changes in channel morphology, flood conveyance and river habitat suitability. Here, we use a large set of high-resolution topographic surveys to assess coarse sediment delivery and routing in the 1,279 km² glaciated White River, Washington State, USA. This study was motivated by the concern that changes in climate may increase coarse sediment delivery from the watershed's volcanic and glaciated headwaters, potentially accelerating chronic deposition in a populated alluvial fan near the river's mouth. However, we find that most of the coarse sediment load in the lower river is derived from erosion of the lower-watershed valley floor, as the river continues to respond to an early-20th century drop in local base-level. Base-level initially declined following a major avulsion across the fan in 1906, an event conditioned by the watershed history of continental glaciation and a massive mid-Holocene lahar, but was then further lowered by dredging along the new channel alignment. In headwater proglacial areas, coarse sediment export has been dominated by infrequent large pulses that blanket downstream valley floors with material. In the periods between these pulses, most bed material transport in the proglacial rivers is sourced from erosion of previously-emplaced valley floor deposits. We suggest coarse sediment fluxes in the lower White River are unlikely to be sensitive to short-term changes in headwater delivery rates, both because punctuated proglacial sediment pulses are attenuated by storage and because headwater delivery is an overall modest component of lower river sediment load. More generally, the introduction of bed material into the White River appears dominated by extreme hydrologic or extra-fluvial (glacial, volcanic) events with 10²-10⁴ year recurrence intervals, while more typical floods primarily redistribute existing stored sediment.
482. Wright et al. (2023) Development of a volcanic risk management system at Mount St. Helens: 1980 to present
     Here, we review volcanic risk management at Mount St. Helens from the perspective of the US Geological Survey’s (USGS) experience over the four decades since its 18 May 1980 climactic eruption. Prior to 1980, volcano monitoring, multidisciplinary eruption forecasting, and interagency coordination for eruption response were new to the Cascade Range. A Mount St. Helens volcano hazards assessment had recently been published and volcanic crisis response capabilities tested during 1975 thermal unrest at nearby Mount Baker. Volcanic unrest began in March 1980, accelerating the rate of advance of volcano monitoring, prompting coordinated eruption forecasting and hazards communication, and motivating emergency response planning. The destruction caused by the 18 May 1980 eruption led to an enormous emergency response effort and prompted extensive coordination and planning for continuing eruptive activity. Eruptions continued with pulsatory dome growth and explosive eruptions over the following 6 years and with transport of sediment downstream over many more. In response, USGS scientists and their partners expanded their staffing, deployed new instruments, developed new tools (including the first use of a volcanic event tree) for eruption forecasting, and created new pathways for agency internal and external communication. Involvement in the Mount St. Helens response motivated the establishment of response measures at other Cascade Range volcanoes. Since assembly during the early and mid-1990s, volcano hazard working groups continue to unite scientists, emergency and land managers, tribal nations, and community leaders in common cause for the promotion of risk reduction. By the onset of renewed volcanic activity in 2004, these new systems enabled a more efficient response that was greatly facilitated by the participation of organizations within volcano hazard working groups. Although the magnitude of the 2004 eruptive sequence was much smaller than that of 1980, a new challenge emerged focused on hazard communication demands. Since 2008, our understanding of Mount St. Helens volcanic system has improved, helping us refine hazard assessments and eruption forecasts. Some professions have worked independently to apply the Mount St. Helens story to their products and services. Planning meetings and working group activities fortify partnerships among information disseminators, policy and decision-makers, scientists, and communities. We call the sum of these pieces the Volcanic Risk Management System (VRMS). In its most robust form, the VRMS encompasses effective production and coordinated exchange of volcano hazards and risk information among all interested parties.
481. Fountain et al. (2023) Inventory of glaciers and perennial snowfields of the conterminous USA
     This report summarizes an updated inventory of glaciers and perennial snowfields of the conterminous United States. The inventory is based on interpretation of mostly aerial imagery provided by the National Agricultural Imagery Program, US Department of Agriculture, with some satellite imagery in places where aerial imagery was not suitable. The inventory includes all perennial snow and ice features ≥ 0.01 km². Due to aerial survey schedules and seasonal snow cover, imageries acquired over a number of years were required. The earliest date is 2013 and the latest is 2020, but more than 73% of the outlines were acquired from 2015 imagery. The inventory is compiled as shapefiles within a geographic information system that includes feature classification, area, and location. The inventory identified 1331 (366.52 ± 14.34 km²) glaciers, 1176 (31.01 ± 9.30 km²) perennial snowfields, and 35 (3.57 km² ± no uncertainty) buried-ice features. The data including both the shapefiles and tabulated results are publicly available at https://doi.org/10.15760/geology-data.03 (Fountain and Glenn, 2022).
480. Schwat et al. (2023) Multi-decadal erosion rates from glacierized watersheds on Mount Baker, Washington, USA, reveal topographic, climatic, and lithologic controls on sediment yields
     Understanding land surface change in and sediment export out of proglacial landscapes is critical for understanding geohazard and flood risks over engineering timescales and characterizing landscape evolution over geomorphic timescales. We used automated Structure from Motion software to process historical aerial photographs and, with modern lidar data, generated a high-resolution DEM time series with coverage over 10 glacierized watersheds on Mount Baker, Washington, USA for the time period between 1947 and 2015. We measured basin-wide sediment yields and sediment redistribution on hillslopes and in stream channels. Slopes within most measured erosion sites are above theoretical and observed debris-flow thresholds. We observed significant erosion of hillslopes and limited deposition on hillslopes and in stream channels. Sediment delivery ratios during time periods with net erosion averaged 0.73. We determined, consistent with previous field observations, that debris flows originating from moraines are a primary erosion mechanism in proglacial zones on Mount Baker. Time series measurements indicate that temporal variability in erosion rates is associated with climate oscillations, with higher erosion rates during cooler-wetter periods. Basin-wide sediment yield is positively correlated with lithology (r2 = 0.54), hillslope angle (r2 = 0.52), drainage area (r2 = 0.82), and negatively correlated with stream channel slope (r2 = 0.67). Topographic differences between high and low yielding basins indicate that spatial variability in erosion on Mount Baker is sensitive to Pleistocene and Holocene glacial and volcanic activity. Specific sediment yields in six basins averaged 4600 ton/km2/yr, consistent with global measurements in glacierized catchments. Specific sediment yield decreased with increasing basin area, with total loads in the downstream main stem Nooksack River estimated between 480 and 820 ton/km2/yr. Proglacial sediment yields account for between 18 and 32 % of total sediment load in the main stem Nooksack River and exceed contributions by bluff and terrace erosion, which account for between 8 and 13 % of total load. Our findings indicate that erosion in glacierized basins is sensitive to decadal climate oscillations and that high proglacial sediment yields provide an important contribution to river systems downstream, particularly in catchments where upland topography and lithology is favorable.

View More Publications...

The U.S. Geological Survey Cascades Volcano Observatory and the Pacific Northwest Seismic Network continue to monitor Washington and Oregon volcanoes closely and will issue additional notifications as warranted.

Website Resources

Mount St. Helens history and hazards: https://www.usgs.gov/volcanoes/mount-st.-helens

Current Mount St. Helens seismicity: https://pnsn.org/volcanoes/mount-st-helens#seismicity
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

Subscribe to these messages: https://volcanoes.usgs.gov/vns2/

Jon Major, Scientist-in-Charge, USGS Cascades Volcano Observatory, jjmajor@usgs.gov, 360-993-8927

Wes Thelen, Geophysicist, USGS Cascades Volcano Observatory, wthelen@usgs.gov, 360-993-8977

Liz Westby, Geologist, USGS Cascades Volcano Observatory, lwestby@usgs.gov, 360-993-8979