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At least 1,567 records · Page 87Linked to original sources
USGS2019

Quantifying erosion rates by using terrestrial laser scanning at Malakoff Diggins State Historic Park, Nevada County, California, 2014–17

The abandoned hydraulic mine pit at Malakoff Diggins near Grass Valley, California, can produce large volumes of eroded sediment transportable by storm runoff. Sediment-laden water discharged from the pit is a major source of heavy metals to Humbug Creek and the South Yuba River. To develop a comprehensive sediment budget for the Malakoff Diggins mine pit and identify sources of sediment and metals within the pit that can become entrained as suspended sediment in runoff discharged from the pit, the U.S. Geological Survey, working in cooperation with the California Department of Water Resources, the California Department of Parks and Recreation, and the Nevada Irrigation District, used terrestrial laser scanning technology to quantify eroded volumes and erosion rates of sedimentary units exposed in the pit walls. The results for eroded volumes and rates reported here are part one of a three-part study. High-resolution terrestrial laser scanning surveys were repeated annually from 2014 through 2017, including before and after dry and wet winters, measuring centimeter-scale topographic changes to quantify the volume of sediment eroded from outcrops at Malakoff Diggins State Historic Park, located on the western slope of the northern Sierra Nevada about 17 kilometers northeast of Grass Valley, California. Terrestrial laser scanning enabled construction of three-dimensional maps of the complex outcrop surfaces, which could not be mapped non-destructively or in sufficient detail with traditional surveying techniques. Eroded volumes from discrete sedimentary units were calculated at four study sites (numbered 1, 2, 4, and 5) throughout the mine pit for the December 2014 to August 2017 period. Eroded volumes at the four study sites during the 32-month study ranged from 288 plus or minus (±) 13 cubic meters (m 3 ) of sediment at site 1 to 8,517±145 m 3 at site 4. Annual erosion rates at the four study sites ranged from 0.06±0.01 cubic meters per square meter per year (m 3 /m 2 /yr) at site 4 to 0.14±0.01 m 3 /m 2 /yr at site 2. The total eroded volume documented with terrestrial laser scanning at all four study sites from December 2014 to August 2017 was 12,934±334 m 3 of sediment, and the average annual erosion rate for the four study sites was 0.10±0.04 m 3 /m 2 /yr. Horizontal erosional-change maps indicate that a variety of erosional processes were responsible for the eroded sediment volume. These included areally broad and smaller-scale processes such as persistent dry ravel, periodic sheet wash, and frost heave and more localized and larger-scale processes such as coalescing fluvial incision, rotational landslides, and translational block-fall failures.

California↗
USGS2021

Implementation plan for the southern Pacific Border and Sierra-Cascade Mountains provinces

Introduction The National Cooperative Geologic Mapping Program (NCGMP) is publishing a strategic plan titled Renewing the National Cooperative Geologic Mapping Program as the Nation’s Authoritative Source for Modern Geologic Knowledge (Brock and others, in press). The plan provides a vision, mission, and goals for the program during the years 2020–2030, which are: Vision .—Create an integrated, three-dimensional, digital geologic map of the United States. Mission .—Characterize, interpret, and disseminate a national geologic framework model of the Earth through geologic mapping. Goal .—Focus on geologic mapping as a core function of the U.S. Geological Survey (USGS) within the long-term vision of adequately mapping the Nation’s geologic framework in three dimensions. In order to achieve the goals outlined in the strategic plan, the NCGMP has developed an implementation plan. This plan will guide the annual review of projects carried out by USGS staff (FEDMAP) described in the plan and the development of the annual FEDMAP prospectus that will ensure the effective application of the NCGMP strategy. This publication describes the implementation plan of the NCGMP strategy for the southern Pacific Border and Sierra-Cascade Mountains provinces, as defined by Fenneman (1917, 1928, and 1946). This implementation plan focuses on the geology of California and a sliver of Nevada surrounding Lake Tahoe. The southern Pacific Border and Sierra-Cascade Mountains provinces encompass the varied landscapes of the high Sierra Nevada, the Central Valley, and Coast Ranges in northern and central California and the Peninsular Ranges, Continental Borderland, Los Angeles Basin-San Gabriel-San Bernardino valleys, western and central Transverse Ranges, and northernmost Salton Trough in southern California. Societal demands create a need for earth-science data in each of these landscapes. The broader San Francisco Bay area, Central Valley, Los Angeles-San Gabriel-San Bernardino lowlands, and the coastal lowlands that border the Peninsular Ranges are densely populated (about 30 million people) areas at high risk of natural hazards. The mountains of the Sierra Nevada, Peninsular Ranges, and Transverse Ranges, and the coast all provide numerous recreational opportunities that attract visitors from around the world, whereas previously these ranges attracted people to mine their resources. The agricultural capacity of the Central Valley is a critical resource for the Nation that is increasingly water limited. The southern. Pacific Border and Sierra-Cascade Mountains provinces, at the edge of the North American continent, were profoundly influenced by subduction zone tectonics during the Mesozoic and early Cenozoic (ongoing in northernmost California) and subsequently by the inception, development, and present activity of the San Andreas transform margin system. Although the geology of this region is the poster child of fundamental conceptual models of subduction zone complexes, forearc basins, ophiolite obductions, magmatic arcs, and suspect terranes, as well as hosting one of Earth’s most notorious continental transform faults—the San Andreas Fault—important questions that have important societal consequences remain to be answered. Most of California’s population reside in these provinces and live within 30 miles of an active fault (according to www.earthquakeauthority.com ) yet new faults continue to be discovered, highlighting the importance of deformation off the main San Andreas Fault. Bedrock, surficial, and three-dimensional (3D) geologic maps depicting stratigraphic structure and depth to crystalline basement rocks provide critical context and information for understanding fault rupture, distributed deformation, fault connectivity, and history in addition to providing crucial data that enable forecasting of shaking amplitude and length from hypothetical earthquake scenarios. The tectonic evolution of California produced not only stunning mountains, with associated hazards from landslides and active volcanoes, but also fertile valleys that make California the top agricultural producer in the country in terms of cash receipts (according to www.ers.usda.gov/faqs ). These valleys lie atop large basins that not only store groundwater but, in many cases, host oil and gas fields, contributing to the fourth highest hydrocarbon production by State in the country in 2016 (according to https://www.aei.org/carpe-diem/animated-chart-of-us-oil-production-by-state-1981-2017 ). Water is a key resource increasingly stressed by growing agricultural, industrial, and residential needs. Warmer and drier conditions have led to an increased reliance on extracting groundwater resources, whose availability and quality are dictated at the first order by the 3D spatial distribution of bedrock and Quaternary surficial deposits. Thus, assessment of this critical resource is inextricably tied to knowledge of the surficial and subsurface geologic structure and material types.

California, Nevada↗
USGS2022

Systematic mapping of the ocean-continent transform plate boundary of the Queen Charlotte fault system, southeastern Alaska and western British Columbia—A preliminary bathymetric terrain model

In 2015, U.S. Geological Survey scientists in collaboration with scientists from other institutions began a study of the Queen Charlotte fault—the first systematic study of the fault in more than three decades. The primary goal of the study was to gain a better understanding of the earthquake, tsunami, and underwater-landslide hazards throughout southeastern Alaska, as well as gather data to develop geologic models that can be applied to similar plate boundaries around the globe, such as the San Andreas fault system in southern California, the Alpine fault in New Zealand, and the North Anatolian fault in Turkey. A bathymetric terrain model was compiled from six different multibeam surveys of the previously unmapped Queen Charlotte fault offshore of southeastern Alaska and Haida Gwaii archipelago.

Alaska, British Columbia↗
USGS2026

Preliminary bedrock geologic map of the Port Henry quadrangle, Essex County, New York, and Addison County, Vermont

Introduction The bedrock geology of the 7.5-minute Port Henry quadrangle consists of deformed and metamorphosed Mesoproterozoic gneisses of the Adirondack Highlands unconformably overlain by weakly deformed lower Paleozoic sedimentary rocks of the Champlain Valley. The Mesoproterozoic rocks occur on the eastern edge of the Adirondack Highlands and represent an extension of the Grenville Province of Laurentia. Mesoproterozoic paragneiss, marble, and amphibolite hosted the emplacement of an anorthosite-mangerite-charnockite-granite (AMCG) suite, now exposed mostly as orthogneiss, at approximately 1.18–1.15 Ga (giga-annum). In the Port Henry quadrangle, the AMCG metaigneous rocks (Yhg, Ygb, Yanw) intruded older, mostly metasedimentary rocks of the Grenville Complex during the middle to late Shawinigan orogeny (~1,160–1,150 Ma [mega-annum]). All rocks were subsequently metamorphosed to upper amphibolite to granulite facies conditions during the 1,080–1,050 Ma Ottawan orogeny. New mapping reveals four periods of deformation: (1) D1 produced rarely preserved isoclinal folds in the paragneiss and marble and predates AMCG magmatism. (2) Subsequent D2 deformation produced the dominant gneissic fabric preserved in the rock, recumbent folding, and deformed all the Proterozoic units in the map area. Syn- to late-D2 felsic magmatism resulted in the regionally extensive Lyon Mountain Granite Gneiss, which hosts numerous magnetite ore bodies. (3) Mylonitic extensional shear zones and core complex formation marked the beginning of D3 deformation. Protracted D3 deformation resulted in F3 upright folding, dome and basin formation, pegmatite intrusion, reactivation of the S2 foliation, partial melting, metamorphism, metasomatism, iron-ore remobilization, and intrusion of magnetite-bearing pegmatite both as layer-parallel sills and crosscutting dikes. (4) D4 created northeast- and northwest-trending local high-grade ductile shear zones and boudinage, northwest-trending regional kilometer (km)-wide ductile shear zones, and crosscutting granitic pegmatite dikes. The development of the late-stage regional shear zones (D4) was likely due to the continuation of extensional doming and uplift from upper amphibolite facies conditions at the end of the Ottawan orogeny. The majority of iron-ore deposits in the Port Henry and adjacent Witherbee quadrangles are in the hanging wall of these extensional shear zones. In the Port Henry quadrangle, the km-wide Cheney Mountain shear zone is the result of D4 deformation. Kilometer-scale lineaments readily observed in lidar data are Ediacaran mafic dikes and Phanerozoic brittle faults. The Paleozoic rocks are part of the Early Cambrian to Late Ordovician carbonate bank on the ancient margin of Laurentia. The approximately 1-km-thick Cambrian to Ordovician stratigraphy records a transition from synrift clastics to passive-margin peritidal carbonate buildups to gradually deeper-water subtidal- to shelf-carbonates during foreland basin development associated with the Taconic orogeny. The Paleozoic rocks are weakly folded and block faulted. Large areas of the Champlain Valley are covered by undifferentiated glacial deposits, some of which contain mapped landslides. The map also shows waste rock piles and tailings from historical mining operations. This study was undertaken to improve our understanding of the bedrock geology in the Adirondack Highlands, establish a modern framework for 1:24,000-scale bedrock geologic mapping in the Adirondacks, provide a context for historical iron mines in the eastern Adirondacks, and update the stratigraphy of the Champlain Valley in New York and Vermont. This Open-File Report includes a bedrock geologic map; a description of map units; a correlation of map units; and a geographic information system database that includes bedrock geologic units, faults, outcrops, and structural geologic information.

New York, Vermont↗
USGS1951

Indian Creek uranium prospects, Beaver County, Utah

The secondary uranium minerals metatorbernite (?) and autunite (?) were discovered at Indian Creek in the spring of 1950. The deposits, in sec. 26, T. 27 S., R. 6 T., Beaver County, Utah, are 20 miles west of Marysvale, and about three-eighths of a mile east of a quartz monzonite stock. The uranium minerals are sparsely disseminated in argillized and silicified earlier Tertiary Bullion Canyon latite and related volcanic rock beneart, but close to, the contact of the overlying later Tertiary Mount Belknap gray rhyolite. The prospects are in a landslide area where exposures are scarce. Therefore, trend and possible continuity of the altered and the uraniferous zones cannot be established definitely. The occurrence of secondary uranium minerals in beidellite-montmorillonite rock, formed by alteration of earlier Tertiary rocks near a quartz monzonite stock, is similar to that in some of the deposits in the Marysvale uranium district.

Open-File Report↗
USGS1956

Geologic investigations of proposed Sheep Creek, Carlson Creek, and Turner Lake power sites, Alaska

Geologic conditions at Sheep Creek, Carlson Creek, and Turner Lake are discussed in relation to possible plans for hydroeletric power development. The proposed sites are on the rugged mainland of Southeastern Alaska along Gastineau Channel and Taku Inlet near Juneau. Bedrock in the area consists of a coastal strip of northwestward-trending foliated metamorphic rocks with steep northeasterly dips. This belt of rocks is adjacent to the Coast Range batholith on the northeast, with a 2 to 3 mile wide zone of injection gneiss between the main batholith and the metamorphic rocks. Unconsolidated glacial and post-glacial deposits of Quaternary age mantle the bedrock over large parts of the area. The valleys of Sheep and Carlson Creeks have been modified by glaciers of Pleistocene age and Turner Lake occupies a rock basin formed by glacial scour. There is an excellent site in greenstone bedrock at Sheep Creek for either a concrete or a rock fill dam. A conduit from the dam to a powerhouse along Gastineau Channel would be on bedrock for most of the distance. Slate bedrock suitable for a powerhouse site is exposed near the mouth of Sheep Creek. To the northwest along Gastineau Channel, bedrock is concealed by a mantle of glacial deposits of unknown thickness. The reservoir is in essentially impermeable bedrock; however, a main haulage adit of the Alaska-Juneau gold mine would probably have to be sealed off to prevent flooding of the mine workings or possible loss of water from the reservoir. The dam, diversion tunnel, and powerhouse at Carlson Creek are all in bedrock consisting of fresh injection gneiss. This rock is well suited as the foundation of a concrete or rock fill dam, but foundation treatment would be required to seal off closely spaced open joints trending perpendicular to the proposed dam axis. The diversion tunnel would stand unsupported except possibly where it would intersect two zones of closely spaced joints. The reservoir would be in essentially impermeable bedrock. Both the main dam and auxiliary structure at Turner Lake would be on an excellent foundation of granitic rock (granodiorite). Loose landslide debris would have to be removed at the dam site to expose fresh, sound bedrock. There is a powerhouse site in bedrock along Turner Creek at a stream elevation of 16 feet. Foundation conditions for a powerhouse at tidewater, near the mouth of Turner Creek were not studied. The conduit would be on sound granitic rock throughout its length, and the reservoir is entirely in relatively tight granitic bedrock.

Alaska↗
USGS1967

A photo-mosaic of western Peru from Gemini photography

The Geological Survey in cooperation with the National Aeronautics and Space Administration and with the Raytheon Company has prepared a mosaic from photographs taken during the Gemini IX mission. The 1:1,000,000-scale photo-mosaic extends from the Sechura Desert in northern Peru to northern Chile and from the Pacific Ocean to the headwaters of the Amazon. In addition to a wide variety of geological features, such things as landslides, roads, snow fields, irrigated lands, jungle agricultural sites, archeological sites, and smoke (brush burning) have been identified on the photo-mosaic. A lineation, interpreted here as a major fault, extends across several photographs and for several hundred miles. The magnitude of this lineation was not realized until the photographs were rectified and the mosaic constructed. For many purposes this mosaic is superior to the best existing 1:1,000,000-scale conventional maps of the area. This mosaic will supplement, not replace, existing conventional maps and aerial photographs. Mosaics of photographs taken from space should be of considerable interest to the scientific community and of immense practical use in the efficient management of natural resources.

Open-File Report↗
USGS1968

Geology of the Gore Canyon-Kremmling area, Grand County, Colorado

The Gore Canyon-Kremmling area is in the southwestern portion of the Kremmling 15-minute quadrangle, Colorado. Precambrian rocks are biotite gneiss, the Boulder Creek Granodiorite, granophyre dikes, and quartz veins. The Boulder Creek intrudes the biotite gneiss, and both of these units are cut by north-northwest-trending granophyre dikes and quartz veins. Biotite gneiss contains structure elements of a northwest and a northeast fold system. Lineations and foliations in the Boulder Creek are generally concordant to the northeast fold system . of the gneiss. Late Paleozoic to Mesozoic and Mesozoic sedimentary formations, in ascending order and with their approximate thicknesses, are the State Bridge Formation, 15 feet; the Chinle and Chugwater Formations undivided, 0-95 feet; the Sundance Formation, 0?-100 feet; the Morrison Formation, 250 feet; the Dakota Sandstone, 225 feet; the Benton Shale, 340 feet; the Niobrara Formation, 600 feet; and the Pierre Shale. Quaternary deposits are terrace, landslide, and modern flood-plain deposits. Laramide rock deformation is related to the Park Range uplift and includes faulting and, in the sediments, some folding. Some of the faults, including the regional Gore fault, are Precambrian structures reactivated in Laramide time.

Open-File Report↗
USGS1970

Flood of August 1969 in Virginia

Hurricane Camille became a tropical depression and soaked central Virginia with up to 28 inches of rain during the night of August 19th and morning of the 20th. The rains, flash floods, and rain-induced landslides accompanying the storm's passage have been called the worst natural disaster ever to strike Virginia. Discharge of streams in the James, Potomac, Rappahapnock, and York River basins exceeded previous known maximums. At Tye River near Lovingston the peak flood discharge was eight times the previous high during the 31 years of record. James River stations downstream from the Maury River recorded peak flows of greater than 100-year recurrence interval. As of Nov. 13, 1969, the State had counted 113 dead and 102 injured with 39 persons still missing. The total damage amounted to over $116 million. This report provides hydrologic data needed for planning and design. The report includes a general description of the flood; precipitation information; sediment aspects of the flood; and records of stage and/or discharge for 105 sites.

Virginia↗
USGS1972

Emergency ground-water supplies in the Seattle-Tacoma urban complex and adjacent areas, Washington

Urban areas that are supplied from surface-water sources are especially vulnerable to major disruption of their water supplies. Such disruption could result from natural disasters such as earthquakes, floods, or landslides or from such other causes as dam failures fallout of radioactive material or other toxic substance from the atmosphere or other toxic substances from the atmosphere or direct introduction (either accidental or deliberate) of any substance that would render the water unfit for use. Prolonged disruption of public water supplies not only causes personal hardships but also endangers health and safety unless suitable alternative emergency supplies can be provided. The degree of hardship and danger generally increases in direct relation to the population density. Ground water because it occurs beneath protective soil and rock materials is less subject to sudden major contamination than are surface-water bodies. For this reason and also because of its widespread availability in the Puget Sound region ground water is especially desireable as a sources of emergency supplies for drinking or other uses requiring water of good quality. In much of the area existing wells would be suitable as safe sources of emergency supplies.

Washington↗
USGS1973

Liquefaction potential of unconsolidated sediments in the southern San Francisco Bay Region, California

A preliminary map of liquefaction potential of unconsolidated sediments has been made for the southern part of the San Francisco Bay region. Map zones are established on the basis of recent detailed geologic mapping. Liquefaction potential for each zone is estimated from an analysis of lithologic, water-table and standard penetration test data. Due to empirical aspects of the evaluation method, approximations in establishing parameters and the generalizations of limited test data to entire map zones, the liquefaction potential map must be considered as~preliminary and approximate. Nevertheless, the map should serve the intended purpose of generally delineating areas where the probability for liquefaction during a major earthquake is greatest and, hence, areas where special attention should be given to the possibility of liquefaction. Sediments with the highest potential for liquefaction are clean granular layers within the younger bay sediments. These layers are not everywhere present but commonly occur locally near present and former stream channels. Clean granular beds and layers immediately beneath the younger bay sediments generally have a lesser but significant potential for liquefaction. Younger (Holocene) alluvial deposits have an even lower potential, however, the potential can be locally high in recent channel and overbank deposits. Part of the Holocene unit is normally above water-table and thus would have only a seasonal potential for liquefaction. Older (Pleistocene) alluvial fan deposits have a generally low liquefaction potential. Lateral spreading landslides are commonly associated with liquefaction beneath gentle slopes. Thus. during a major earthquake. slides of this type would probably be the most pervasive damaging effect of liquefaction on the broad alluvial plain surrounding San Francisco Bay.

California↗
USGS1976

A preliminary evaluation of selected earthquake-related geologic hazards in the Kenai Lowland, Alaska

Several major faults exist beneath the Kenai Lowland, and others may be inferred. No surface evidence was found to indicate that any of the faults have been active in Holocene time. The sparse shallow seismicity thus far recorded does not correlate with known faults, nor does it define linear trends suggestive of faulting. Tidal flats at the mouths of the Kenai, Kasilof, and Chickaloon Rivers have been uplifted in the Holocene, however, and the uplift may reflect growing anticlines at depth. Some faults associated with folding may be active, but they are probably too limited in size to generate destructive earthquakes. They could, however, constitute a hazard to manmade structures in their immediate vicinity. Vibrational damage and ground failure during the 1964 earthquake were most extensive north of Tustumena Lake in areas of water-saturated unconsolidated deposits with uneven topography. South of Tustumena Lake, damage resulted mainly from landslides formed along unconfined bluffs and riverbanks, and from submarine sliding and subsidence at Homer Spit. A comparable distribution of surficial effects may be anticipated in future large earthquakes on the Kenai Lowland.

Alaska↗
USGS1977

Reconnaissance report of geotechnical observations for the 4 March 1977 Romanian earthquake

A catastrophic earthquake struck south central Romania at 21:21 hours (9:21 p.m.) local time, March 4, 1977. The tremor collapsed 33 multistory buildings in Bucharest and damaged many other structures to varying degrees. Important damage was inflicted on many other cities and villages, particularly Craiova and Zimnicea. (For locations, see Fig. 1) Over 1,500 deaths resulted from the shock. The epicenter of the shock was preliminarily located at 45.85° N, 26.73° E with a focal depth of 110 km. A preliminary magnitude of 7.2 was assigned to the event. Aftershocks up to approximately magnitude 4 have spread south westward from the epicenter (approximately as far south as Buzau). The focal depths of aftershocks in the southern part of the zone were shallower than the main shock (as shallow as 50 km). A team of nine United States scientists and engineers was sent by the U. S. State Department to make a reconnaissance investigation of earthquake effects and damage. The team consisted of; Charles Culver (team leader) and George Fattal, National Bureau of Standards; Gerald Bowles and Fred Ruud, Bureau of Reclamation; Ernest Dodson, Army Corps of Engineers; Ted Algermissen Chris Rojahn and Les Youd, U. S. Geological Survey; and Karl Steinbrugge, Insurance Services office and a consultant to U.S.G.S. Upon arrival in Romania, the team was divided into groups which generally specialized in the following areas: Culver and Fattal investigated structural damage to buildings. Algermissen and Steinbrugge investigated the general distribution of damage and types of buildings affected in Bucharest. Dodson, Bowles and Ruud investigated damage to dams and hydroelectric power plants. Rojahn collected strong motion records and initiated discussions with the Romanians on the possible development of additional strong motion seismographs. Youd investigated damage to foundations and occurrences of ground failure (landslides, etc.). The groups worked independently of each other. However, there was communication between groups during joint meetings with various Romanian officials and in the evening hours. The purposes of this report are: 1. To summarize geotechnical effects of the earthquake. 2. To outline and justify a proposed United States Romanian cooperative geotechnical program which was considered as part of a broader cooperative program in engineering and seismology. 3. To provide a log of my travels.

Open-File Report↗
USGS1977

Summary of watershed conditions in the vicinity of Redwood National Park, California

The Redwood Creek Unit of Redwood National Park is located in the downstream end of an exceptionally rapidly eroding drainage basin. Spatial distribution and types of erosional landforms, observed in the field and on time-sequential aerial photographs, measured sediment loads, and the lithologic heterogeneity of streambed materials indicated (1) that sediment discharges reflect a complex suite of natural and man-induced mass movement and fluvial erosion processes operating on a geologically heterogeneous, naturally unstable terrain, and (2) that although infrequent exceptionally intense storms control the timing and general magnitude of major erosion events, the loci, types, and amounts of erosion occurring during those events are substantially influence by land use. Erosional impacts of past timber harvest in the Redwood Creek basin reflect primarily the cumulative impact of many small erosion problems caused not so much by removal. Recently modified riparian and aquatic environments reflect stream channel adjustments to recently increased water and sediment discharges, and are classified by the National Park Service as damaged resources because the modifications reflect, in part, unnatural causes. Newly strengthened State regulations and cooperative review procedures result in proposed timber harvest plans being tailored to specific site conditions, as well as smaller, more dispersed harvest units and more sophisticated attempts at minimizing ground-surface disruption than those used in most previous timber harvesting in this basin. However, application of improved timber harvest technology alone will not assure protection of park resources. Much remaining intact residual commercial old-growth timber is on hillslopes that are steeper, wetter, more susceptible to landsliding, and more nearly adjacent to major stream channels than most of the previously harvested hillslopes in the lower Redwood Creek basin. Moreover, natural debris barriers along streams flowing through remaining old-growth forest have temporarily stored substantial quantities of sediment introduced into streams by recent storms and upstream land-use changes. Removal of merchantable timber from these barriers may destroy their stability and cause rapid release of stored sediment. Additionally, massive erosion in some recently harvested areas suggest that they are so erosionally sensitive that following rehabilitation and reforestation, they should not be reharvested. Thus, in order to maintain site productivity and to protect downstream park resources, some erosionally critical areas may have to be maintained as perpetual timber reserves dedicated to watershed protection. Selective Federal acquisition of just erosionally critical acreage would create ownership patterns that would make management of both parklands and commercial timber lands exceedingly difficult.

California↗
USGS1978

Development of a technique for the rapid estimation of earthquake losses

A simple, general technique has been outlined for the rapid, approximate estimation of building losses resulting from ground shaking during earthquakes. The technique has been applied to the San Francisco Bay area. Ground shaking, ground failures of various kinds, surface faulting, tsunamis, and earthquake induced fires are all responsible for earthquake building losses. Only losses associated with ground shaking are considered in this report for a number of reasons. Losses associated with various types of ground failure such as landsliding and liquefaction are difficult to estimate because the conditions necessary for these effects to occur are not completely understood and/or may be difficult to identify. Losses related to surface faulting are believed to be small as a proportion of total losses (Algermissen and others, 1972), and losses related to tsunamis have been quite rare along the central California coast. Well-established methods are available for estimating fire losses, but these losses are beyond the scope of this report.

California↗
USGS1978

Proceedings of Conference V: communicating earthquake hazard reduction information: convened under auspices of National Earthquake Hazards Reduction Program 22-24 May, 1978

Under the Earthquake Hazard Reduction Act of 1977, the federal government is significantly increasing its effort "to reduce the risk of life and property from future earthquakes in the United States through the establishment and maintenance of an effective earthquake hazards reduction program". This prgoram is sponsored primarily by the U.S. Geological Survey and the National Science Foundation and includes research by geologists, geophysicists, seismologists, engineers, sociologists, educators, and public policy experts. In the USGS program, there is a strong emphsis on effective communication of the results of research to a wide community of decision makers and users. This action is the key to implementation at all levels in federal, state, and local government, in the private sector, and on an individual basis. The U.S. Geological Survey convened a workshop involving approximately 65 people on May 22-24, 1978 in Denver, Colorado, to examine the communication problem. The purpose of the workshop was to evaluate critically the information-flow process for a number of past experiences, including: (1) land use planning in Portola Valley, California, (2) the seismic safety element, Santa Clara County, California (3) earthquake preparedness, Puget Sound, Washington area, (4) mitigation of geological hazards in Colorado, (5) earthquake planning in the Mississippi-Arkansas-Tennessee area, (6) water resource and land use planning in the northeast United States, (7) acquiring and disseminating scientific and engineering information following an earthquake, (8) development, use, and review of geologic and seismological data fro sitting of nuclear power plants, (9) development and use of building codes that incorporate earthquake provisions, (10) use of research products produced in the HUD/USGS San Francisco Bay region study, and (11) achieving landslide hazard reduction. The objective was to identify the most significant lessons learned during the course of each experience and to develop recommendations for improving communication that might be incorporated in the search program of the USGS.

Open-File Report↗
USGS1979

Preliminary report on Tertiary volcanism and uranium mineralization in the Thomas Range and northern Drum Mountains, Juab County, Utah

The Thomas Range and northern Drum Mountains have a history of volcanism, faulting, and mineralization that began about 42 m.y. ago. Volcanic activity and mineralization in the area can be divided into three stages according to the time-related occurrence of rock types, trace element associations, and chemical nature of mineralization. Volcanic activity switched abruptly from rhyodacite-quartz latite (42-39 m.y. ago) to rhyolite (38-32 m.y. ago) to alkali rhyolite stages (21 and 6-7 m.y. ago); these stages correspond to periods of chalcophile and siderophile metal mineralization, no mineralization, and lithophile metal mineralization, respectively. Angular unconformities record episodes of cauldron collapse and block faulting between the stages of volcanic activity and mineralization. The youngest angular unconformity formed between 21 and 7 m.y. ago during basin-and-range faulting. Early rhyodacite-quartz latite volcanism from composite volcanoes and fissures produced flows, breccias, and ash-flow tuff of the Drum Mountains Rhyodacite and Mt. Laird Tuff. Eruption of the Mt. Laird Tuff about 39 m.y. ago from an area north of Joy townsite was accompanied by collapse of the Thomas caldera. Part of the roof of the magma chamber did not collapse, or the magma was resurgent, as is indicated by porphyry dikes and plugs in the Drum Mountains. Chalcophile and siderophile metal mineralization, including copper, gold, and manganese, accompanied early volcanism. The middle stage of volcanic activity was characterized by explosive eruption of rhyolitic ash-flow tuffs and collapse of the Dugway Valley cauldron. Eruption of the Joy Tuff 38 m.y. ago was accompanied by subsidence of this cauldron and followed by collapse and sliding of Paleozoic rocks from the west wall of the cauldron. Landslides in The Dell were covered by the Dell Tuff, erupted 32 m.y. ago from an unknown source to the east. An ash-flow of the Needles Range Formation was erupted 30-31 m.y. ago, probably from a distant source outside the volcanic field. The rhyolitic stage of volcanism was barren of mineralization. The last stage of volcanism was contemporaneous with basin-and-range faulting and was characterized by explosive eruption of ash and pumice, forming stratified tuff, and by quiet eruption of alkali rhyolite as viscous flows and domes. The first episode of alkali rhyolite volcanism deposited the beryllium tuff and porphyritic rhyolite members of the Spor Mountain Formation 21 m.y. ago. After a period of block faulting, the stratified tuff and alkali rhyolite of the Topaz Mountain Rhyolite were erupted 6-7 m.y. ago along faults and fault intersections. Erosion of Spor Mountain may have provided abundant dolomite detritus to the beryllium tuff member. The alkali rhyolite of both formations is fluorine-rich, as is evident from abundant topaz, and contains anomalous amounts of lithophile metals. Alkali rhyolite volcanism was accompanied by lithophile metal mineralization which deposited fluorite, beryllium, and uranium. The structure of the area is dominated by the Thomas caldera, and the younger Dugway Valley cauldron, which is nested within the Thomas caldera; the Thomas caldera is surrounded by a rim of Paleozoic rocks at Spor Mountain and Paleozoic to Precambrian rocks in the Drum Mountains. The Joy fault and Dell fault system mark the ring fracture zone of the Thomas caldera. These structural features began to form about 39 m.y. ago during eruption of the Mt. Laird Tuff and cauldon subsidence. The Dugway Valley cauldron sank along a series of step-like normal faults southeast of Topaz Mountain in response to collapse of the magma chamber of the Joy Tuff. The caldera structure was modified by block faulting between 21 and 7 m.y. ago, the time of widespread extensional faulting in the basin-and-range province. Vents erupted alkali rhyolite 6-7 m.y. ago along basin-and-range faults. Uranium mineralization was associated with the stage of alkali rhyolite volcanism, extensional basin-and-range faulting, and lithophile metal mineralization; it occurred at least 11 m.y. after the end of the caldera cycle. Uranium, derived from alkali rhyolite magma, was concentrated in trace amounts by magmatic fluids and in potentially economic amounts by hydrothermal fluids and ground water. Hydrothermal fluids deposited uraniferous fluorite as pipes in carbonate rocks of Paleozoic age on Spor Mountain and uranium-bearing disseminated deposits of fluorite and beryllium in the beryllium tuff member of the Spor Mountain Formation. Uranium of hydrothermal origin is dispersed in fluorite and opal. Uranium in fluorite may be tetravalent(?) but that in opal is probably hexavalent; no primary minerals of tetravalent uranium are known to occur. Ground waters have concentrated significant ores of hexavalent uranium minerals in the beryllium tuff member of the Spor Mountain Formation at the Yellow Chief Mine, and are probably also responsible for widespread low concentrations (0.0X percent) of uranium that occur separately from beryllium ore in the beryllium tuff member. More deposits of the Yellow Chief type may occur in down-faulted sections of beryllium tuff beneath the Thomas Range. The ground water ores show no evidence of a reducing environment; instead, precipitation of hexavalent uranium minerals occurred by evaporation, decline in concentration of complexing ions such as carbonate, or some other mechanism. Reducing environments for hydrothermal deposits must be sought around rhyolite vents and in a hypothesized pluton of alkali rhyolite composition beneath Spor Mountain; for ground-water deposits, reducing environments may occur in basin fill such as that of the Dugway Valley cauldron.

Utah↗
USGS1979

A Late Pleistocene and Holocene pollen record from Laguna de las Trancas, northern coastal Santa Cruz County, California

A 2.1-m core from Laguna de las Trancas, a marsh atop a landslide in northern Santa Cruz County, Calif., has yielded a pollen record for the period between about 30,000 B.P. and roughly 5,000 B.P. Three pollen zones are recognized; the earliest is characterized by high frequencies of pine pollen and is correlated with a mid-Wisconsinan interstade of the mid-continent. The middle zone contains high frequencies of both pine and fir (Abies, probably A. grandis) pollen and is correlated with the last full glacial interval (upper Wisconsinan). The upper zone is dominated by redwood (Sequoia) pollen and represents latest Pleistocene to middle Holocene. The past few thousand years are not represented in the core. The pollen evidence indicates that during the full glacial period the mean annual temperature at the site was about 2 ° C to 3 ° C lower than it is today. We attribute this small difference to the stabilizing effect of marine upwelling on the temperature regime in the immediate vicinity of the coast. Precipitation may have been about 20 percent higher as a result of longer winter wet seasons.

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