Geology topics

Research about United States

Source-linked reports with geographic coverage including United States.

At least 55 records · Page 3Linked to original sources

USGS2026

Human factors used to estimate and forecast water supply and demand in the Delaware River Basin

The objective of this report by the U.S. Geological Survey is to identify cultural and economic determinants of water demand, supply, and access, and to locate associated datasets of those determinants. Although climate and its influence on hydrology are important components of water availability, this study focused only on the components of the human system. The Delaware River Basin (the area including Delaware Bay, and parts of four States including Delaware, New Jersey, New York, and Pennsylvania) was used as a proxy. The basin covers approximately 13,600 square miles, supplies agricultural, municipal, and industrial water, and provides jobs for millions of people in the region. The most salient social and economic determinants affecting current water availability, as well as existing data sources on those determinants, were identified through a literature review. Regional water availability results from complex interactions of water supply and demand, as well as hydrological and climatological interactions between institutions and economics. Following the definition of water availability from Herman-Mercer and others (2023), “access to a specific quantity and quality of water at a point in time and space, for a specific use, recognizing the social and economic value of water across uses and institutions that facilitate or hinder its impartial and efficient provisioning,” we identify human determinants influencing water supply and demand and provide examples from the extensive datasets available to estimate these determinants in the agricultural, municipal, and industrial water-use sectors, using the Delaware River Basin as a case study. We also reference determinants related to recreation and ecosystem services that influence water availability in the Delaware River Basin. Gaps were found pertaining to best practices for prioritization of human determinants within water-availability assessments and a lack of consistent data collection across different scales. A major focus of the work identified a need to prioritize collection and refinement of the human determinants to improve water availability estimation and forecasting. We ascertained that predictions of water use in these sectors often fall short. Predictions may use approximations for changes in demand, such as population or economic activity. Changes in demand also may be influenced by political or other strategic behavior, which are more difficult to incorporate into predictions. Approximations and other assumptions about water supply and demand can be improved to better predict water availability. Therefore, there is an opportunity to further understand and use the fundamental human determinants of water supply and demand along with changing climate variables to predict water availability in the future.

Delaware, New Jersey, New York, Pennsylvania↗

USGS2026

Methods for the computation of streamflow statistics for selected streamgages in or near Nevada through water year 2021

Streamflow statistics are used by Federal, State, and local agencies to protect and manage the water resources of Nevada. Peak-streamflow, low-streamflow, streamflow-duration, mean, minimum, and maximum streamflow statistics were computed for 310 streamgages in Nevada and surrounding States through water year 2021 (the period from October 1, 2020, to September 30, 2021) by the U.S. Geological Survey. Trend analyses of a subset of 54 active streamgages with at least 30 years of data that were minimally affected by human activities indicated that most sites had “somewhat likely downward” or “likely downward” trends for peak, mean, and low streamflow. Statistically significant (probability value less than 0.05) negative trends were associated with peak streamflow at 12 percent of sites, annual mean streamflow at 31 percent of sites, and annual 7-day average low streamflow at 28 percent of sites. Statistically significant positive trends were associated with peak streamflow at 2 percent of sites, annual mean streamflow at 3 percent of sites, and annual 7-day average low streamflow at 9 percent of sites. Comparisons with previously computed statistics determined that changes in computational methods, the length of the streamgage record, and instance of wetter than average periods were the most influential on the computed statistics.

Arizona, California, Idaho, Nevada, Oregon, Utah↗

USGS2026

Updates to the Lake Washington Ship Canal and Ballard Locks model, Seattle, Washington, 2016–20

The Hiram M. Chittenden Locks (Ballard Locks or Locks) and Lake Washington Ship Canal connect freshwater Lake Washington with saline Shilshole Bay of Puget Sound. The Locks are operated by the U.S. Army Corps of Engineers (USACE) and serve commercial and recreational vessels. Anadromous salmonids migrate through the canal by making use of a fish ladder at the Locks. To help understand canal hydrodynamics, water temperature, and salinity, a two-dimensional model (CE-QUAL-W2) of the Locks and Lake Washington Ship Canal was constructed by WEST Consultants, Inc. In cooperation with USACE, the U.S. Geological Survey reviewed and updated this model and documentation. The review, published previously, recognized the strengths of the model and suggested some modifications and updates. This report documents these modifications, reports on sensitivity testing, describes model recalibration, and reports model results for calendar years 2016–20. Modeled water velocity was less than 0.2 meter per second at most sites and depths; velocity was greater nearer the Locks. Water age, which estimates residence time, was greatest during September and October. Water temperature was greater near-surface and cooler near the channel bottom at some times and locations. The model also simulated the inflow of lower-salinity waters from Lake Washington and the import of higher-salinity waters from the Locks.

Washington↗

USGS2026

An extensive and short-lived episode of mid-Holocene fayalite- bearing high-silica rhyolite eruptions at Mono Craters, California

Having last erupted ~ 700 years ago, the Mono Craters volcanic chain is an active system with a history of explosive and effusive high-silica rhyolite eruptions. Approximately ~ 30 lava domes and flows range from ~ 42 to ~ 0.7 ka, form a ~ 15 km curvilinear trend, and change mineralogy (biotite-, orthopyroxene-, or fayalite-bearing) and crystallinity through time. However, the eruptive chronology of this system is incompletely understood. We report new 238 U- 230 Th isochron ages for nine fayalite-bearing domes from paired zircon and allanite crystal surfaces that reveal a major shift in eruptive frequency and volume over the history of the chain, with extrusion of > 0.45 km 3 of high-silica rhyolite lava between 7.1 and 5.2 ka. This contrasts with older biotite- (~ 42–20 ka) and orthopyroxene-bearing (~ 12–9 ka) domes, each of which erupted smaller volumes over a more protracted period. Whole-rock compositions suggest these older domes tapped separate domains within a shared magmatic system because the former are higher in Sr and Ba whereas the latter are lower in SiO 2 , higher in Zr, and more enriched in light rare-earth elements. Titanomagnetite chemistry and zircon saturation temperatures also reflect changing magma compositions and conditions associated with these domes. Fayalite-bearing domes, in contrast, have uniform whole-rock and titanomagnetite compositions which support rapid extrusion of magma over an interval short enough to prevent Fe-Ti oxides from recording any changes in magmatic conditions. The youngest lavas were also produced in a short-lived episode ~ 700 years ago, showing that multivent, geologically brief eruptive episodes occur repeatedly at Mono Craters.

California↗

USGS2026

Water depth fluctuations and water chemistry in five ephemeral rock pools (tinajas), Clark County, Nevada, 2021–23

Southern Nevada is characterized by an arid climate with limited perennial water resources. In this environment, rock pools (tinajas) are both a habitat and drinking water source for wildlife. In this reconnaissance-level project, the U.S. Geological Survey studied the water depth and water chemistry at five tinajas in Clark County, Nevada. The tinaja sites in this study are representative of the dominant plunge pool morphology and the sandstone or carbonate bedrock substrates that characterize tinajas in the region. Continuous water depth measurements at four tinajas between December 2021 and December 2023 indicated that tinajas may contain water for weeks to months after being recharged but are not a permanent drinking water source for wildlife. Tinajas were driest between April and August 2022, before the beginning of the monsoon season. Chemical analysis of select nutrients, major ions, metals, and trace elements from five tinajas detected concentrations below limits established by the U.S. Environmental Protection Agency for aquatic life and drinking water.

Nevada↗

USGS2026

Springs of the Catskill Mountains: A conduit flow system in predominantly siliciclastic strata

The Catskill Mountains of New York state are composed of thick sequences of interbedded mudstone, sandstone, and siltstone that are intercalated with thin beds of paludal limestone and calcareous mudstone. Sandstones often contain rip-up clasts of calcareous material at their bases and contain minor amounts of carbonate cement throughout their mass. This minor amount of calcareous material weathers out to produce thin zones of solutional porosity and permeability integrated within perched aquifers that feed perennial hillslope springs. Solutional features are evident within thin carbonate lenses and along fractures in sandstones, occasionally resulting in explorable cave-sized conduits. This study focuses on the behavior of bedrock springs and seeps in the headwaters of the Neversink River basin above the Neversink Reservoir. Bedrock springs are numerous throughout the Catskill Mountains and serve to provide baseflow to the headwater streams that tends to be more persistent during dry times than other baseflow sources. We observed dissolution-influenced conduits within the bedrock, and suffosional conduits within unconsolidated materials. Continuous water temperature at six springs was monitored at hourly intervals from May to October 2022 to investigate the thermal response of groundwater to daily and seasonal changes in air temperature along with event-based meteorological events. Temperature monitoring was augmented at some springs with time-lapse photography to evaluate persistence of flow. The thermal responses of springs to precipitation events were highly variable across sites, with some springs exhibiting flashy responses indicating a strong connection to the surface, while other springs showed muted or no thermal response to events. The seasonal thermal response also varied across sites having lag times of 23-48 days between peak air temperature and peak spring water temperature. The water temperatures and geochemical compositions of these bedrock springs support a conceptual model of multiple residence times, showing both event and seasonal groundwater storage within the conduit flow system that feeds the springs of the Catskill Mountains.

New York↗

USGS2026

How tough a passage? Nonnative fish entrainment survivability at a major dam in the western USA

The Colorado River downstream of Glen Canyon Dam (GCD) in the southwest USA demonstrates anthropogenic modification including altered flow and temperature regimes and established nonnative species in upstream reservoirs. Water overallocation and megadrought are contributing to new potential invasion pathways for nonnative fishes through dam releases. In this study, we quantified factors that influence survival of fish entrained at GCD, a pathway for nonnative fishes to leave Lake Powell and enter the Grand Canyon as reservoir levels remain near historic lows since the reservoir initially filled. We measured conditions of entrainment through GCD using a mechanical Sensor Fish device and evaluated potential barotrauma by comparing our results to previous studies. Under measured conditions, a fish's gas bladder would expand by a factor of 2.7 due to entrainment, potentially resulting in injury from barotrauma. We estimated members of Centrarchidae may survive entrainment at problematically high rates across all water levels where entrainment is expected. Minimizing nonnative fish entrainment through GCD is best achieved through maintenance of water levels higher than those in recent years, potentially decreasing both entrainment likelihood and survival.

Arizona↗

USGS2026

Production of secondary microbial methane from a gas hydrate-bearing reservoir at the HYDRATE P1 Production Test Well (PTW-1) on the Alaskan North Slope

Gas hydrate in the Alaskan North Slope (ANS) is believed to contain as much methane as the known conventional gas accumulations in the Prudhoe Bay field. The JOGMEC-DOE-USGS Collaborative Gas Hydrate R&D Project conducted an extended-duration production test from the sub-permafrost, gas-hydrate saturated B1 sand reservoir (unit B) at the Kuparuk State 7-11-12 Site in the Prudhoe Bay Unit of the ANS. Using compositional and stable isotopic data measured on gas produced from well cuttings and pressure cores collected from the HYDRATE 02 Geo Data Well (GDW), we differentiate primary microbial, secondary microbial, and trace thermogenic gas sources. The upper part of the well contained predominantly primary microbial methane from near the surface to the SV6 stratigraphic horizon at 1133 ft (345.3 m) measured depth (MD). Below that, the gas composition transitioned to a mixture of mostly primary and secondary microbial methane to near the base of ice-bearing permafrost at 1968 ft (599.8 m) MD. With greater depth to 3558 ft (1084.5 m) MD, which includes the D1 sand (unit D), the B1 sand (unit B), and the base of gas hydrate stability at 3113 ft (948.8 m) MD, the gas composition was greater than 98% secondary microbial methane with the remainder being oil-associated thermogenic gas migrated from the deep Sadlerochit Formation. The unit B vertical gas profile derived from degassed pressure cores demonstrated that gas dissolved in the clay-rich sediment intervals bounding the B1 sand reservoir was distinct from dissolved and hydrate-caged gases in the sand-rich hydrate-bearing reservoir. The HYDRATE P1 Production Test Well (PTW-1) targeted and successfully extracted gas dissociated from hydrate gas in the B1 sand for 151 days when using an electrical submersible pump to depressurize the reservoir with subsequent depressurization achieved through the use of a jet pump. Gas produced from PTW-1 was mostly indistinguishable from the gas compositional profile measured through the B1 sand and generally distinct from dissolved gas in the bounding clay-rich sediments, confirming that the upper and lower bounding units limited infiltration into the reservoir during production. Isolation of the bounding units from the reservoir contributed to the unexpectedly high ratio of production gas to water observed during the extended-duration gas hydrate production test at PTW-1.

Alaska↗

USGS2026

Multiple lines of evidence reveal rapid, seasonal watershed responses to enhanced weathering

Enhanced weathering accelerates carbon dioxide removal from the atmosphere through the rapid dissolution of land amendments of crushed, cation-rich rocks. The export of enhanced weathering dissolution products to drainage networks has important implications for carbon dioxide removal durability and measurement yet has received little attention. Here we observe rapid and pronounced streamwater chemistry responses within weeks of a crushed basalt application to a temperate headwater catchment: alkalinity exceeded counterfactual estimates by as much as 557 μeq l −1 , accompanied by changes in silica, lithium and major-ion chemistry consistent with basalt weathering. Difference-in-differences analysis identified repeated treatment effects with enhanced weathering accounting for 7–17% of streamwater alkalinity in successive summers and autumns, but less in winter and spring. This seasonal response reflects a combination of temperature controls on basalt dissolution kinetics and hydrologic controls on weathering-product export. Over 2 years, 9.5–11% of theoretical carbon dioxide removal potential was exported as alkalinity (34.7 t CO 2 km −2 yr −1 ).

Vermont↗

USGS2026

Tapwater contaminant mixtures and cumulative risk screening on the Crow (Apsáalooke) Reservation

Introduction: Water insecurity is a challenge for the Apsáalooke (Crow) Tribal Nation in south-central Montana, United States. Both private-well and public-supply tapwater (TW) are vulnerable to a range of contaminants, posing potential risks to community health and well-being. Ongoing community concerns about unrecognized inorganic, organic, and microbial contaminants underscore the need for continued comprehensive monitoring and improved water management strategies. Materials and methods: TW samples were collected from 26 private-well and 12 public-supply participant locations, selected and recruited by the Crow Water Quality Project. A total of 35 inorganic, 450 organic, and three microbial analytes were assessed in these samples. Public-Supply Maximum Contaminant Levels and Health benchmark-based screening levels were used to evaluate contaminant concentrations. Results: Sixty-one organic and 34 inorganic contaminants were detected. Screening levels were frequently exceeded, particularly due to multiple inorganic contaminants in private TW and both chlorine-based disinfection byproducts (DBPs) and inorganics in public TW. These findings highlight gaps in current source-water protection and water treatment practices. Conclusions: After reporting results to participants, anonymized data were shared at community events to inform risk management decisions. The study underscores the importance of broad monitoring and analysis throughout the upper Missouri River basin and across the United States to address Tribal concerns over water insecurity and mitigate potential unrecognized TW contaminant risks, particularly to vulnerable subpopulations.

Montana↗

USGS2026

Floods of June 20–July 6, 2024, in the Big Sioux River, Rock River, Little Sioux River, Ocheyedan River, and Floyd River Basins, northwestern Iowa

Major flooding occurred on June 20–July 6, 2024, in northwestern Iowa affecting the Big Sioux, Rock, Little Sioux, Ocheyedan, and Floyd River Basins. Heavy rain fell in northwestern Iowa, southwestern Minnesota, and southeastern South Dakota on June 20–22, 2024. Parts of northwestern Iowa recorded 2–6 inches of rainfall and localized amounts exceeding 12 inches. A maximum peak-of-record streamflow of 175,000 cubic feet per second at the U.S. Geological Survey streamgage Big Sioux River at Akron, Iowa (06485500), was recorded on June 22, 2024, and had an annual exceedance probability range of 0.2–0.49 percent. High-water marks were measured at four locations along the Big Sioux River between U.S. Interstate 29 at Sioux City, Iowa, upstream to Iowa Highway 10 north of Hawarden, Iowa, a distance of 75.7 river miles. A maximum peak-of-record streamflow of 157,000 cubic feet per second at the U.S. Geological Survey streamgage Rock River near Rock Valley, Iowa (06483500), was recorded on June 22, 2024, and had an annual exceedance probability of less than 0.2 percent. High-water marks were measured at eight locations along the Rock River between County Road B30 east of Hudson, South Dakota, upstream to Iowa Highway 9 at Rock Rapids, Iowa, a distance of 39.3 river miles. A maximum peak-of-record streamflow of 63,000 cubic feet per second at the U.S. Geological Survey streamgage Little Sioux River at Correctionville, Iowa (06606600), was recorded on June 24, 2024, and had an annual exceedance probability range of 0.2–0.49 percent. High-water marks were measured at 11 locations along the Little Sioux River between Iowa Highway 31 west of Correctionville, Iowa, upstream to U.S. Highway 18 north of Spencer, Iowa, a distance of 134.8 river miles. A maximum streamflow of 24,500 cubic feet per second at the U.S. Geological Survey streamgage Ocheyedan River near Spencer, Iowa (06605000), was recorded on June 22, 2024, and had an annual exceedance probability range of 0.2–0.49 percent. High-water marks were measured at three locations along the Ocheyedan River between County Road M38 west of Spencer, Iowa, upstream to U.S. Highway 18 west of Everly, Iowa, a distance of 12.8 river miles. A maximum streamflow of 41,000 cubic feet per second at the U.S. Geological Survey streamgage Floyd River at Alton, Iowa (06600100), was recorded on June 22, 2024, and had an annual exceedance probability range of 1–1.99 percent. High-water marks were measured at six locations along the Floyd River between Iowa Highway 3 at Le Mars, Iowa, upstream to Iowa Highway 10 at Alton, Iowa, a distance of 27.5 river miles. The high-water marks were used to develop flood profiles for the Big Sioux, Rock, Little Sioux, Ocheyedan, and Floyd Rivers.

Iowa, Minnesota, South Dakota↗

USGS2026

Anthropogenic and geogenic factors affecting groundwater arsenic and potential drinking water exposure in the San Luis Valley, Colorado

Groundwater arsenic is a serious health threat in many regions with limited surface water drinking supplies. In the San Luis Valley, Colorado, USA, where most residents rely on groundwater for drinking water, elevated groundwater arsenic concentrations (≥5 μg/L) were observed in 19.8% of private wells. Many recent studies have leveraged data science methods to estimate the spatial variability of arsenic at local, regional, and global scales. These studies typically predict depth-independent arsenic concentrations due to limited well depth information. However, arsenic concentrations may vary greatly with depth due to heterogeneous aquifer geochemistry, including redox potential, pH, and biogeochemical conditions. In this study, we apply random forest modeling to predict elevated groundwater arsenic concentrations (≥5 μg/L) over space and depth continuously across the San Luis Valley using a community-driven data set of 435 groundwater measurements of major ions and trace metals. Our model reveals the influence of several known or hypothesized drivers or proxy drivers of arsenic in groundwater, including surface elevation, fraction of fine-grained aquifer sediments, well depth, soil pH, long-term subsidence, and geothermal influences. Elevation, percentage of fine-grained sediments, and elemental indicators of geothermal fluid influence are some of the most important predictors of arsenic, while long-term subsidence is found to have a weak but positive relationship with arsenic. The model has a specificity of 0.82 and a sensitivity of 0.81 on held-out test data sets. In addition to improving understanding of drivers of arsenic in the region, this model produces pseudo-3D estimates of groundwater arsenic. The model can also be used to assess the time-dependent exposure to arsenic as the depth of domestic wells changes over time.

Colorado↗

USGS2026

Describing Yellow Perch population characteristics in Wisconsin to better understand observed declines in size structure

Objective Recent studies suggest that Yellow Perch Perca flavescens size structure has declined in Wisconsin and Minnesota. Little is known about most of the Yellow Perch populations that exist across the upper Midwestern USA because Yellow Perch are not a focus of standardized sampling and age estimation rarely occurs. To better understand Yellow Perch population dynamics and demographics, we described age- and length-based characteristics of 31 Yellow Perch populations in Wisconsin and assessed potential correlations with abiotic and biotic variables. Methods During 2018–2019, Yellow Perch were collected from 31 populations during spring fyke-net surveys to calculate mean total length (TL) at age 4 (ML4), maximum age, proportional size distribution (PSD), and mean TL of the five largest fish (MXL5). Pearson correlations were used to identify associations among these metrics and with a suite of abiotic and biotic variables. Results Mean TL at age 4 was <175 mm for 54% of our study populations, median maximum age was 8 years, median PSD was 15, and median MXL5 was 229 mm TL. There were positive correlations among ML4, PSD, and MXL5 and between maximum age and MXL5. Yellow Perch metrics were not correlated with catch per effort of Walleye Sander vitreus , Largemouth Bass Micropterus nigricans , or Bluegill Lepomis macrochirus . Yellow Perch population metrics were generally not correlated to environmental variables except for ML4, which was positively correlated to shoreline development index and maximum age, which was negatively correlated to growing degree-days and lake surface area. Conclusions Many Wisconsin Yellow Perch populations we evaluated were slow growing with low size structure and limited capacity to produce fish ≥200 mm TL. Populations where PSD is ≥32 and MXL5 ≥245 mm TL may represent exceptional opportunities for anglers to catch relatively large fish and could warrant additional investigation to identify factors contributing to high size structure.

Wisconsin↗

USGS2026

Pre-eruptive volatiles and magma storage depth for the 2018 eruption at Mount Veniaminof, Alaska

Mount Veniaminof is a frequently active, open-system arc volcano on the Alaska Peninsula, part of the Alaska-Aleutian arc. Mount Veniaminof's September–December 2018 eruption began with small lava flows and culminated in a larger explosive event in November that produced a 450 km long continuous ash plume—one of the volcano's most significant ash-producing events in recently observed eruptions. A temporally constrained tephra record was sampled after the eruption. We present volatile element concentrations (H, C, S, Cl, F) from a total of 65 olivine-hosted melt inclusions (MIs) across six tephra layers to assess potential variations in magma chemistry throughout the course of the eruption. No variation is observed in volatile concentrations across the tephra layers, and there is no correlation between volatile concentrations and the explosivity of eruptive pulses leading to the November explosive event. H 2 O concentrations within MI suggest moderately hydrous magmas up to 2.4 wt% H 2 O and a large range in CO 2 concentrations in the MI (14–2,180 ppm) from Secondary Ion Mass Spectrometry and vapor bubble reconstructions. H 2 O and CO 2 measurements correspond to entrapment pressures up to 400 MPa (entrapment depths ∼15 km), but with modal storage around 100–200 MPa. H 2 O contents can be reconciled with previous microlite number density estimates using a polybaric storage history.

Alaska↗

USGS2026

Solar energy development selectively filters avian taxonomic and functional diversity across a perennial agricultural landscape

Solar energy is rapidly expanding across agricultural landscapes, yet its consequences for avian communities remain poorly understood, particularly among heterogeneous land-use matrices. In 2024 and 2025, we surveyed birds across 107 sites in New York State, including conventional solar arrays with mowing or sheep grazing to manage vegetation, solar-adjacent working lands (e.g. hayfields, pastures) and reference working lands independently located from solar arrays. We integrated diversity metrics across four trait dimensions—taxonomic, morphological, ecological and conservation status—and examined interactions between species-level abundance and traits to understand avian community responses to solar energy development. Avian species in solar sites tended to be common, non-migratory (in behaviour and wing morphology) and associated with shrubland or forest. Compared to reference working lands, bird communities in solar and solar-adjacent sites were less taxonomically diverse and were composed of fewer declining and range-restricted species. However, solar and solar-adjacent sites retained comparable diversity of intrinsic traits, suggesting that ecological function may persist despite apparent species filtering and functional reshuffling. While solar energy development can support avian communities with unique functional signatures, our findings suggest that conventional solar arrays sited on agricultural working lands in New York maintain low bird diversity and are unlikely to support conservation-priority species—such as grassland birds characterized by declining populations, migratory tendencies and open-habitat dependence. Synthesis and applications . Our study provides a pathway to leverage functional diversity to quantitatively characterize solar-associated avian communities and the ecological mechanisms that shape them. Our results suggest that meeting biodiversity conservation goals while achieving solar energy targets requires ecologically informed siting and processes, particularly across regions in which co-prioritization of conservation, agriculture and energy presents sustainability trade-offs.

New York↗

USGS2026

Stability changes after weak layer collapse: Insights from an unexpected dataset

While conducting avalanche mitigation or traveling through the backcountry, avalanche professionals sometimes experience a "whumpf": a collapse-mode crack accompanied by surface cracking that does not produce an avalanche. These whumpfs are a clear warning sign of instability in the surrounding terrain. But assessing the collapsed slope itself, if it is steep enough to avalanche, carries much more uncertainty. Can slopes that whumpf and are steep enough to slide still avalanche? The answer to this question supports avalanche mitigators and ski guides in assessing whether to open such slopes. Previous research on collapsed slopes is limited to one study conducted before tests that estimate crack propagation propensity, such as the Propagation Saw Test (PST), were developed. This work showed that weak layer shear strength decreased immediately after collapsing and then increased over time. However, no research has examined crack propagation propensity after a whumpf. Studying propagation propensity is key for assessing how whumpfs immediately affect slope stability. To improve our understanding of changes in propagation propensity following weak layer collapse, we conducted PSTs on a test slope in the hours and days after an unexpected collapse occurred on a layer of surface hoar. Two PSTs at our study site three days prior to this collapse provided an estimate of weak layer propagation propensity. PST cut lengths decreased immediately following the collapse, suggesting that the collapse increased the propagation propensity. However, over the next 4-5 hours, PST cut lengths steadily increased at our site, likely due to ongoing sintering and strengthening in the collapsed weak layer. By the end of day two, we were no longer able to initiate propagation, suggesting substantial stabilization of the weak layer. Our results support prior findings and observations suggesting that slopes may remain capable of producing avalanches immediately after a collapse but likely stabilize over the next day or two. Although this research does not provide answers about precisely when a slope becomes stable after a collapse, it does highlight uncertainties in our understanding and interpretation of the stability of slopes that have whumped.

Montana↗

USGS2026

Start-zone characteristics and timing of wet slab avalanches In Colorado

Wet slab avalanches (WSAs) release when liquid water reduces the strength of a buried weak layer or interface, and their timing is governed primarily by the snowpack energy balance and the movement of meltwater. We classified 717 WSAs from the Colorado Avalanche Information Center database (2011–2025) into five start-zone terrain categories and analysed the timing of naturally triggered, near- and above-treeline events using rank-based and Bayesian hierarchical methods. Start-zone terrain strongly governs the natural occurrence of WSAs: approximately 64% released in Rocky start zones (Cliffs/Rocks), while only ≈4% occurred on Open Slopes. After controlling for latitude and aspect, Rocky start zones released approximately five days before Open Slopes (90% CrI: 0.6–9.9 days). Latitude was the dominant timing predictor, shifting release by roughly 3–4 weeks from southern to northern Colorado. Cornice start zones concentrated WSA activity in early to mid-spring, with 40 of 41 releasing before mid-May. These findings support start-zone terrain classification as a low-cost addition to observation protocols for improving the spatial targeting of wet slab outlooks.

Colorado↗

USGS2026

Patterns of glide avalanche release: Insights from 23 years of observations along the Going-to-the-Sun Road, Montana, USA

Glide avalanches pose a notable hazard during annual spring snow removal operations along the Going-to-the-Sun Road (GTSR) in Glacier National Park (GNP), USA. Glide cracks consistently form on specific slopes near and above the GTSR. Some glide crack locations produce glide avalanches most years (known as repeater paths), whereas others are less predictable and either release or melt in place. Previous studies of glide avalanches have focused on different meteorological, snow-pack, and terrain parameters that influence glide release. The timing of glide avalanche release remains difficult to predict, which can be a challenge. To the authors' knowledge, no previous work has approached the issue of timing by comparing the chronological release order of glide paths within an operation. To address this, we examine the release order of repeater paths along the GTSR and investigate different topographical factors that may influence release timing. To investigate the timing of glide avalanche release, we analyzed a dataset of annually recorded glide avalanches from 2003 to 2025 along the GTSR from mid-March to June. We identified 359 glide avalanches with starting zones covering all aspects between 1,600 and 2,700 meters, and performed analysis on topographic factors including elevation, aspect, slope angle, and bed surface. Additionally, we assessed the likelihood and sequence of the release of seven repeater paths. Seven repeater paths along the GTSR generate glide avalanches nearly every year (65–100% of the study period), with two paths (Peak 7774 and Peak 7850) releasing first in over half of the years observed (p-value < 0.01). These paths have been informally recognized as "indicator paths," though this distinction has not been quantified until now. Identifying factors that drive the timing of glide avalanches using a days-scale operational signal can support the safeguarding of infrastructure and personnel. By examining release order and related variables, this study provides practical insights to inform operations managing glide avalanche hazards. Our methods may help forecasters pinpoint indicator paths and potentially recognize the onset of glide avalanche cycles, offering a framework for other operations.

Montana↗