Geology topics
Research about Montana
Source-linked reports with geographic coverage including Montana.
Ground-water resources in the central part of the Flathead Indian Reservation, northwestern Montana
No abstract available.
Grinnell and Sperry Glaciers, Glacier National Park, Montana: A record of vanishing ice
Grinnell and Sperry Glaciers, in Glacier National Park, Mont., have both shrunk considerably since their discovery in 1887 and 1895, respectively. This shrinkage, a reflection of climatic conditions, is evident when photographs taken at the time of discovery are compared with later photographs. Annual precipitation and terminus-recession measurements, together with detailed systematic topographic mapping since 1900, clearly record the changes in the character and size of these glaciers. Grinnell Glacier decreased in area from 530 acres in 1900 to 315 acres in 1960 and to 298 acres in 1966. Between 1937 and 1969 the terminus receded nearly 1,200 feet. Periodic profile measurements indicate that in 1969 the surface over the main part of the glacier was 25-30 feet lower than in 1950. Observations from 1947 to 1969 indicate annual northeastward movement ranging from 32 to 52 feet and generally averaging 35-45 feet. The annual runoff at the glacier is estimated to be 150 inches, of which approximately 6 inches represents reduction in glacier volume. The average annual runoff at a gaging station on Grinnell Creek 1.5 miles downvalley from the glacier for the 20-year period, 1949-69, was 100 inches. The average annual precipitation over the glacier was probably 120-150 inches. Sperry Glacier occupied 800 acres in 1901; by 1960 it covered only 287 acres, much of its upper part having disappeared from the enclosing cirque. From 1938 to 1969 certain segments of the terminus receded more than 1,000 feet. Profile measurements dating from 1949 indicate a lowering of the glacier surface below an altitude of 7,500 feet, but a fairly constant or slightly increased elevation of the surface above an altitude of 7,500 feet. Along one segment of the 1969 terminus the ice had been more than 100 feet thick in 1950. According to observations during 1949-69, average annual downslope movement was less than 15 feet per year in the central part of the glacier and slightly more rapid toward the edges and at higher parts on the glacier.
Statistical analyses of surface-water-quality variables in the coal area of southeastern Montana
Since 1974 a network of water-quality stations has been operated in the coal area of southeastern Montana. This report updates a previous report with 2 years of additional data collection and presents statistics and regression equations for water-quality variables. The most apparent feature of the study is the variability of water quality. Time-trend differences are most noticeable, with areal differences being present but more subtle. In comparing stations at the mouths of the five major drainages entering the Yellowstone River from the study area, water from the Powder River ranks near the middle of the group in dissolved-solids concentration (mean of 1,390 mg/L), but far exceeds the other drainages in suspended-sediment concentration, often exceeding 10,000 mg/L. The Tongue River generally has the best overall quality with respect to dissolved constituents; extremes are moderated by mixing in the Tongue River Reservoir. Suspended sediment ranged from 5 to 4,360 mg/L. Rosebud Creek shows about a 50-percent average increase in dissolved-solids concentration from the most upstream station to the mouth. Armells and Sarpy Creeks, smallest of the five drainages, have a pool-riffle configuration that influences both dissolved and suspended constituents. Pools permit greater evaporation, thus increasing dissolved-constituent concentrations. They also act as sediment traps. (USGS)
Streamflow characteristics of the Yellowstone River Basin, Montana, through 1976
Statistical summaries of streamflow data for selected stream-gaging and crest-stage gage sites are presented in this report to aid in appraising the hydrology of the Yellowstone River basin, Montana. Streamflow records presented for 45 gaging stations and 45 crest-stage gages for the period of record. Streamflow record collection in the Yellowstone River basin began in 1889. For each gaging station selected for this report, a brief description is given for station location, drainage area , period of record, revisions of previously published records, type and history of gages, regulation and diversions, and extremes of discharge. These data are followed by tables of monthly and annual flow statistics, high-flow and low-flow frequency data, flood-frequency data, flow-duration information, and for natural-flow sites selected basin characteristics. For each crest-stage gage, the brief description consists of location, drainage area, period of record, and type and history of gage. This information is followed by tables of flood-frequency data and selected basin characteristics.
Simulation of water-quality data at selected stream sites in the Missouri River Basin, Montana
Modification of sampling programs at some water-quality stations in the Missouri River basin in Montana has eliminated the means by which solute loads have been directly obtained in past years. To compensate for this loss, water-quality and streamflow data were statistically analyzed and solute loads were simulated using computer techniques. Functional relationships existing between specific conductance and solute concentration for monthly samples were used to develop linear regression models. The models were then used to simulate daily solute concentrations using daily specific conductance as the independent variable. Once simulated, the solute concentrations, in milligrams per liter, were transformed into daily solute loads, in tons, using mean daily streamflow records. Computer output was formatted into tables listing simulated mean monthly solute concentrations, in milligrams per liter, and the monthly and annual solute loads, in tons, for water years 1975-78.
Geothermal gradients in the Missoula and Bitterroot Valleys, west-central Montana
Temperature-depth profiles of six cased test holes in the Missoula and Bitterroot Valleys, west-central Montana, consist of linear segments, the intersections of which commonly correspond with lithologic boundaries. Geothermal gradients commonly decreased with depth, probably as a result of compaction and higher quartz content of the deeper sedimentary deposits. There is no evidence for hydrothermal discharge. A maximum temperature of 31.7 degrees Celsius was measured at a depth of 869 meters. Estimated temperatures at a depth of 1 kilometer at the drill sites ranged from about 34 to 63 degrees Celsius. Temperatures exceeding 90 degrees Celsius probably would not occur at depths less than 1,500 meters. Values of thermal conductivity needed to maintain an assumed regional heat flow of about 2.1 heat flow units along the measured geothermal gradients generally exceeded published values for the rock and soil penetrated by the wells. Laboratory determinations of the thermal conductivity of cores and cuttings would be useful to refine the estimates and to test the conclusion that the measured temperatures are not hotter than normal. (USGS)
Sulfate reduction in ground water of southeastern Montana
Ground water in southeastern Montana was investigated to determine if sulfide production was bacterially mediated. Sulfate—reducing bacteria were detected in 25 of 26 ground—water samples in numbers ranging from 2.0 x 10 1 to greater than 2.4 x 10 4 bacteria per 100 milliliters. Stable sulfur isotope fractionation studies indicate a biological role in sulfate reduction. However, sulfate—reducing activity as determined by use of a radioactive sulfur isotope was observed in only 1 of 16 samples. Bacterial dissimilatory sulfate reduction is postulated to be responsible for a major part of the sulfide produced in these ground waters. These bacteria are most likely active in the adsorbed state, possibly in subsurface microzones where environmental conditions are conducive to sulfate reduction.
Draft environmental statement, proposed Colstrip project, Rosebud County, Montana
No abstract available.
Proposed mining and reclamation plan, Pearl Mine, Big Horn County, Montana: Draft environmental statement
No abstract available.
Geologic map and coal sections of the Forks Ranch quadrangle, Big Horn County, Montana
The Forks Ranch quadrangle lies on the gently-dipping east flank of the Powder River basin, near its trough line.
Restored stratigraphic cross sections and coal correlations in the Tongue River member of the Fort Union Formation, Powder River area, Montana
Exposures of the lower two thirds of the Tongue River Member of the Paleocene Fort Union Formation were measured along the Powder River valley in southeastern Montana in the Moorhead and Birney-Broadus coalfields. This report documents the stratigraphic variations, lateral continuity of partly eroded coal beds along the line of section, and shows ten sections for the Tongue River Member in this study area. This report is a companion to the report by Flores and Canavello (1979). The study area represents a linear distance of 35 miles along the Powder River valley and extends from the Wyoming-Montana State line to a point 7 miles southeast of Broadus. Mont. (see index map). Within this area are relatively continuous outcrops of the middle and lower parts of the Tongue River Member.