SEARCH · Search USGS
Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Thurston Peninsula, although largely snow covered, exposes massive to foliated dioritic rock and schist exhibiting northeast-trending structures. One basalt pebble was found. The adjacent continental shelf is cut by submarine valleys. Peter I Island, a dissected basaltic volcano 250 miles to the northeast, was visited.
Five areas of outcrop were examined along 120 miles of the coast of the Bellingshausen Sea east of the Thurston Peninsula. Hornblende quartz diorite is the principal rock in the area and occurs in a body of batholithic dimensions. The quartz diorite contains inclusions of older granulitic rock and is cut by mafic dikes. An island in Paradise Harbor on the Palmer Peninsula was also examined briefly.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Executive Summary This report reflects our knowledge regarding the widespread landslide activity associated with Hurricane Helene observed during the U.S. Geological Survey’s (USGS) mission assignment to North Carolina in October 2024. The material in this report was originally prepared for the Federal Emergency Management Agency under mission assignment DR-4827-NC. The data and commentary in this report are reflective of a report provided to the Federal Emergency Management Agency (FEMA) on October 18, 2024, as well as information provided in briefings at the Buncombe County Emergency Operations Center. The report has been modified for public dissemination. This assessment was based on systematic visual examination and mapping of landslide locations from aerial and satellite imagery, visual and photographic observations from low-level helicopter overflights and conversations with local landslide experts from the North Carolina Geological Survey and Appalachian Landslide Consultants PLLC, and more than 50 years of combined landslide hazard professional experience of the mission-assigned field team. No systematic field investigations were done by the USGS. While responding to the event, the USGS did not identify any landslides that posed an immediate major threat to recovery personnel in parts of nine counties in North Carolina (Avery, Buncombe, Henderson, McDowell, Mitchell, Polk, Rutherford, Watauga, and Yancey); however, threats from renewed landslide activity may remain heightened in localized areas for months or even years. Known areas of the most abundant landslide occurrence include Bat Cave, Lake Lure, Chimney Rock, Swannanoa, Black Mountain, Fairview, steep areas in Asheville, and the Blue Ridge Parkway. The USGS shared detailed locations of known landslides with the Emergency Operations Centers. The thousands of landslide scars on hillsides and landslide deposits on flatter ground may present some threat to recovery activities. Soil and rocks will continue to erode from newly exposed landslide scars and may pose a threat to people and infrastructure who are immediately nearby. In general, the steeper and taller the landslide scar, the greater the potential threat. This threat is heightened during periods of rainfall and increases with the duration and intensity of rainstorms. Very heavy rainfall, or repeated rainfall events during short periods, could also initiate new landslides on steep slopes. Excavation of landslide deposits, particularly excavation of those deposits directly adjacent to steep slopes, may also pose a threat to nearby people and equipment. An interagency collaborative mapping effort led by the USGS that informed this assessment identified 1,155 landslide locations by the October 2024 briefings, but that number increased to 2,217 in a final reviewed version of the locations published in January 2025. Locations were mapped from satellite imagery, fixed-wing and helicopter surveys, media and social media, and field reports in the 3 weeks following the passage of the remnants of Hurricane Helene. USGS products outlined in this report are publicly available and include geotagged photographs from aerial reconnaissance, hazard models, an interactive view of mapped landslide locations, and landslide safety and education resources.
Explore the source record for details and available documents.
No abstract available.
Intense faulting and fracturing in the Harris Lake area) northeastern Minnesota are documented by detailed field studies. Faults are identified chiefly by the disruption of mappable layers within sequences of plagioclase and plagioclase-olivine cumulates. Most layers grade from olivine-rich bottoms to plagioclase-rich tops and were probably deposited by density currents. Faults trend principally N35?E, N05?W, and N40?W. The recognition of intense faulting and fracturing in this region and an understanding of the currents responsible for cumulate deposition establish a basic geologic framework with important local and regional implications.
Data showing results of 38 groundwater and 25 surface-water samples analyzed for hexavalent chromium are presented. Most samples were taken within the Telluride, Colo., city limits during October 1978. Twenty-four of the 38 groundwater samples (63%) contained more than 50 micrograms per liter of hexavalent chromium. Excluding the mill tailings pond 6 of the 23 surface-water samples (26%) contained more than 50 micrograms per liter of hexavalent chromium. Hexavalent chromium concentrations in groundwaters ranged from 0 to 2700 micrograms per liter and in surface waters from 0 to 160 micrograms per liter.
Geohydrologic data that may be used to predict the effects of mining on Navajo water resources in the San Juan structural basin are reported as well as the current availability of data from other government agencies. Emphasis is on the vicinity of Crownpoint, New Mexico.
Explore the source record for details and available documents.
A subsurface clay dike and hydraulic seals were constructed in 1979 by the Ohio Department of Natural Resources, Division of Reclamation, to reduce acid mine drainage from an abandoned drift mine into Big Four Hollow Creek; Big Four Hollow Creek flow into Sandy Run, the major tributary to Lake Hope. A monitoring program was established in 1979 by the U.S. Geological Survey, Water Resources Division to evaluate sealing effects on surface-water and ground-water systems fo the Big Four Hollow Creek and Sandy Run area just below the mine. Data were collected by private consultants in 1970-71 near the mouth of Big Four Hollow Creek (U.S. Geological Survey station (03201700). Results showed an average pH of 3.1 (calculated from mean hydrogen-ion concentration in moles per liter) and a pH range of 2.7 to 4.8. The estimated sulfate load was 1,000 pounds per day, and the estimated iron load wsa 100 pounds per day. Data collected in 1979, before dike construction at this site, showed a daily mean pH range of 3.4 to 5.4 with an average of 3.7, and a daily mean specific-conductance range of 160 to 600 micromhos per centimeter at 25 degrees Celsius (?mho/cm), averaging 400. Again, the estimated sulfate load was 1,000 pounds per day, but the estimated iron load had decreased to 50 pounds per day. The first 6 months of postconstruction data from the site in 1980 showd a daily mean pH range of 4.5 to 6.8 with an average of 4.9, and a daily mean conductance range of 175 to 405 ?mho/cm with an average of 300. The estimated sulfate load had decreased to 570 pounds per day and the iron load to 8.5 pounds per day. Data collected during the first 6 months after construction indicate moderate improvement in water quality. However, acidic water is still being impounded behind the dike and seals and has not yet been flushed ou by infiltrating rain and ground water. Because the system has not yet stabilized, no interpretation or conclusive statement can be made at this time.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
No abstract available.
The fauna and flora preserved in two cores, 19A and 19B, from the south side of Russell Bank (N 25 03.831', W 80 37.486') in north-central Florida Bay, Everglades National Park, Florida, record a history of environmental change over the last century. The benthic foraminifera and molluscs indicate fluctuating salinities with increasing average salinity upcore in core 19B. Shifts from low salinity (12-15 ppt) to higher average salinity (30 ppt) occurred at 70-66 cm and 24-18 cm in core 19B (approximately 1937-1940 and 1975-1980). The inverse, shifts from periods of higher average salinity to periods of lower salinity, occurred at 140 cm, 90 cm, and 42 cm (approximately 1880, 1921, and 1960). Significant changes in the molluscan fauna indicative of specific substrate types occur at 88 cm, 68 cm, and 22 cm. The lower portion of the core is dominated by a mixture of sediment and grass dwellers, the middle portion by sediment dwellers, and the upper portion of the core by grass and finally grass and algae dwellers. Changes occur in the floral assemblages in core 19A, but the significance of these changes is unclear. Three subtle shifts occur in the pollen assemblages indicating the onshore vegetation was responding to some environmental factor. Two peaks in dinocyst abundance occur in core 19A, but the composition of dinocyst assemblages remains relatively stable throughout the core. Correspondence between changes in salinity and onshore vegetation changes is consistent with results from previous cores. The pattern of increased salinity upcore is consistent with patterns seen in core T24 from the mouth of Taylor Creek and in core 6A from Bob Allen mudbank.
No abstract available at this time
Explore the source record for details and available documents.