Geology topics

Research about Idaho, Montana, Nebraska, North Dakota, South Dakota, Wyoming

Source-linked reports with geographic coverage including Idaho, Montana, Nebraska, North Dakota, South Dakota, Wyoming.

3 recordsLinked to original sources

USGS2025

Predicted fish vulnerability to stream drying in the western U.S.A.

The frequency, magnitude and extent of stream drying is increasing due to climate change and human water demand. Fish vulnerability to increased stream drying is a combination of sensitivity (innate tolerance to low streamflow) and exposure to stream drying. To understand fish tolerance to low flow and susceptibility to decline under changing streamflow conditions, we estimated species-specific measures of sensitivity to low streamflow, determined relationships to species traits and evaluated vulnerability to future reductions in streamflow for 60 species. We found that sensitivity varied across species, and some variation was explained by life history strategy, spawning strategy and body size. Periodic life history strategy, pelagic spawning and larger size corresponded to an increased sensitivity to stream drying. Under future projections of August streamflow, 90% of sites were predicted to decrease in flow magnitude. Vulnerability to changes in streamflow, the combination of sensitivity and exposure, varied slightly across the study species, with the percent of inhospitable sites under future climate scenarios increasing for 87% of the species. Despite being relatively insensitive to low streamflow, vulnerability was high for multiple species dominant in mountainous areas, driven by high levels of exposure to stream drying. Our results illustrate the potential for species traits to predict sensitivity to low streamflow and demonstrate that exposure may play a large role when defining species vulnerability to stream drying. The ability to predict species tolerances and susceptibility to decline will become increasingly important in prioritising conservation efforts under changing environmental conditions.

Idaho, Montana, Nebraska, North Dakota, South Dako↗

USGS2022

Antecedent climatic conditions spanning several years influence multiple land-surface phenology events in semi-arid environments

Ecological processes are complex, often exhibiting non-linear, interactive, or hierarchical relationships. Furthermore, models identifying drivers of phenology are constrained by uncertainty regarding predictors, interactions across scales, and legacy impacts of prior climate conditions. Nonetheless, measuring and modeling ecosystem processes such as phenology remains critical for management of ecological systems and the social systems they support. We used random forest models to assess which combination of climate, location, edaphic, vegetation composition, and disturbance variables best predict several phenological responses in three dominant land cover types in the U.S. Northwestern Great Plains (NWP). We derived phenological measures from the 25-year series of AVHRR satellite data and characterized climatic predictors (i.e., multiple moisture and/or temperature based variables) over seasonal and annual timeframes within the current year and up to 4 years prior. We found that antecedent conditions, from seasons to years before the current, were strongly associated with phenological measures, apparently mediating the responses of communities to current-year conditions. For example, at least one measure of antecedent-moisture availability [precipitation or vapor pressure deficit (VPD)] over multiple years was a key predictor of all productivity measures. Variables including longer-term lags or prior year sums, such as multi-year-cumulative moisture conditions of maximum VPD, were top predictors for start of season. Productivity measures were also associated with contextual variables such as soil characteristics and vegetation composition. Phenology is a key process that profoundly affects organism-environment relationships, spatio-temporal patterns in ecosystem structure and function, and other ecosystem dynamics. Phenology, however, is complex, and is mediated by lagged effects, interactions, and a diversity of potential drivers; nonetheless, the incorporation of antecedent conditions and contextual variables can improve models of phenology.

Idaho, Montana, Nebraska, North Dakota, South Dako↗

USGS1967

Devonian of the Northern Rocky Mountains and plains

The Devonian System, represented predominantly by shallow-water marine carbonate, is widespread in Montana, Wyoming, eastern Idaho, North Dakota, South Dakota, and northwestern Nebraska. It comprises cratonic rocks in the east and miogeosynclinal rocks in the west. The cratonic rocks thicken generally northward from their southern limit in Wyoming across a broad shelf that occupies most of Wyoming and Montana. In northern Montana, they are as much as 1,250 feet thick. Cratonic rocks also thicken eastward from areas of Early Mississippian erosional thinning in central and eastern Montana to as much as 2,000 feet in the intracratonic Williston basin centered in northwestern North Dakota. The miogeosynclinal rocks, which moved eastward on low-angle thrust faults, abut against cratonic rocks along a north-trending disturbed belt in western Wyoming, western Montana and eastern Idaho. The miogeosynclinal rocks thicken abruptly westward from 1,000 feet near this belt to about 3,000 feet near the east edge of the Idaho batholith. Farther west they have been buried beneath younger rocks, altered by the batholith, or eroded. Five subdivisions of the Devonian System are treated separately: 1. Upper Lower Devonian (Coblenzian) marginal and nearshore marine carbonate rocks and related continental and estuarine discontinuous sinkhole and channel-fill deposits. 2. Upper Middle Devonian (Givetian) carbonate rocks that contain a 525-foot-thick evaporitic sequence in the Williston basin. 3. Lower Upper Devonian (Frasnian, toI ) cyclically deposited carbonate rocks that include thick beds of dolarenite and dolomitized calcarenite on the west. 4. Upper Upper Devonian (Famennian, toII-IV ) evaporitic rocks overlain by fossilferous open-marine shale and limestone. 5. Undivided uppermost Devonian (Famennian, to V-VI ) and lowermost Mississippian (Tournaisian, cuI-lower cuII α ) carbonaceous and clastic rocks deposited in six shallow basins interspersed among areas uplifted during the penecontemporaneous Antler orogeny.

Idaho, Montana, Nebraska, North Dakota, South Dako↗