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At least 37 records · Page 2Linked to original sources
USGS1910

Field investigations of structural materials; Structural materials available in the vicinity of Minneapolis, Minnesota; Structural materials available in the vicinity of Austin, Texas; The slates of Arkansas; The oolitic limestone industry at Bedford and Bloomington, Indiana: Supplementary notes on the granites of New Hampshire: Oolitic limestone at Bowling Green and other places in Kentucky; Survey publications on building stone and road metal; Cement materials in Republican Valley, Nebraska; Gravel and sand in the Pittsburg district, Pennsylvania; Survey publications on cement and cement and concrete materials; Fuller's earth and brick clays near Clinton, Massachusetts; Survey publications on clays, fuller's earth, etc.; The gypsum deposits of the Palen Mountains, Riverside County, California; Gypsum deposits near Can Springs, Kern County, California; Survey publications of gypsum and plasters; Survey publications on lime and magnesite; Survey publications on glass sand and glass making materials; Survey publications on abrasive materials

No abstract available.

Bulletin↗
USGS1990

Hydrology, aquatic macrophytes, and water quality of Black Earth Creek and its tributaries, Dane County, Wisconsin, 1985-86

An intensive data-collection program for the Black Earth Creek basin in southern Wisconsin was conducted from October 1984 through September 1986 to assess the hydrology, aquatic macrophytes, and water quality in Black Earth Creek by the U.S. Geological Survey, in cooperation with the Wisconsin Department of Natural Resources. Three sites on two cold-water trout streams Black Earth Creek at Cross Plains, Black Earth Creek near Cross Plains, and Garfoot Creek near Cross Plains were continuously monitored for streamflow and water-quality data. One site in a warm-water stream, Brewery Creek at Cross Plains, also was monitored. Aquatic macrophyte biomass was determined for three sites on Black Earth Creek. Streamflow at Black Earth Creek at Black Earth during the 1985 and 1986 water years (WY) were 44 and 60 percent greater than the long-term mean discharge of 33.3 ft3/s (cubic feet per second) for the period 1955-86. Water year 1986 had the highest annual mean discharge, 53.4 ft3/s, since records began in 1954 at the most downstream site Black Earth Creek at Black Earth. Although there have been considerable fluctuations in streamflow, it has tended to increase since WY 1965 as a result of above-average precipitation and consequent rising ground-water levels. Trout population densities may be related to annual mean streamflow. A regression analysis of adult trout populations and the 3-year moving annual mean discharge had a correlation coefficient of 0.75 with a standard error of 83 percent. Aquatic macrophyte biomass in Black Earth Creek was substantially less in 1986 than in 1985 as a result of substrate scouring from the flood of July 25, 1985. The frequency of occurrence of species during 1985 and 1986 was similar to that of 1981, and seasonal succession of species also was similar; Potamogeton crispus dominated early in the year and senesced in July. P. crispus and P. pectinatus, both indicative of eutrophic conditions, dominated upstream and downstream, respectively; neither species is native to the area. In 1985, the greatest biomass was found upstream from Cross Plains. This large biomass caused diurnal fluctuations in dissolved-oxygen concentration of 5 to 6 mg/L (milligrams per liter) as a result of photosynthesis and respiration. Many of the dissolved-oxygen minimums, recorded at night, were less than the State 6.0-mg/L water-quality standard for trout waters. Discharge from point sources may adversely affect Black Earth Creek's water quality. Warm water discharged to Black Earth Creek from a gravel pit operation upstream from Cross Plains increased water temperatures 2 to 4 degrees Celsius and decreased the dissolved oxygen about 1 mg/L at a site 1.8 miles downstream. Runoff from a settling pond from a landfill operation in the headwaters of the Black Earth Creek basin drains through a wetland that drains to Black Earth Creek and contained as much as 60 mg/L ammonia nitrogen, 980 mg/L biochemical oxygen demand, and 1,300 mg/L chemical oxygen demand, which may be detrimental to trout. Garfoot Creek had the highest suspended-sediment and phosphorus yields per unit area of the three upstream basins during low to moderate runoff. Detention ponds in the Brewery Creek basin appear to be less effective in controlling suspended-sediment and phosphorus loads during periods of high runoff than during moderate runoff. Brewery Creek had the highest concentrations of suspended sediment and total phosphorus during low and high flows. The water quality at the Black Earth Creek gaging station at Black Earth was affected by Garfoot Creek and unnamed tributaries. As a result, yields of suspended sediment, phosphorus, and nitrogen increased between Cross Plains and Black Earth. High streamflows during WY 1985 resulted in suspendedsediment yields at Black Earth Creek at Black Earth that were 29 percent greater than the 12-year (1955-65, 85-86) mean; yields ranged from 69.5 ton/mi2 (tons per square mile) in Black Earth Creek at Cross Plains to 116 ton/mi2 in the Brewery Creek basin. Phosphorus yields ranged from 312 lb/mi2 (pounds per square mile) in Black Earth Creek at Cross Plains to 628 lb/mi2 in the Brewery Creek basin. Total nitrogen yields ranged from 3,280 lb/mi2 in the Brewery Creek basin to 6,920 lb/mi2 in the Garfoot Creek basin. An increase in oxygen demand, caused by agricultural runoff, has resulted in reduced dissolved-oxygen content of the water in both Black Earth and Garfoot Creeks. The most substantial reduction occurred at Black Earth Creek at Cross Plains on July 25, 1985, as a result of the largest storm runoff event during the study. A rainfall of 5.54 inches caused streamflow discharges to increase from 9 to 122 ft3/s and dissolved-oxygen concentrations to decline to 3.0 mg/L; the dissolved-oxygen concentration was less than 6.0 mg/L for 30 hours.

Wisconsin↗
USGS2014

A deposit model for carbonatite and peralkaline intrusion-related rare earth element deposits

Carbonatite and alkaline intrusive complexes, as well as their weathering products, are the primary sources of rare earth elements. A wide variety of other commodities have been exploited from carbonatites and alkaline igneous rocks including niobium, phosphate, titanium, vermiculite, barite, fluorite, copper, calcite, and zirconium. Other elements enriched in these deposits include manganese, strontium, tantalum, thorium, vanadium, and uranium. Carbonatite and peralkaline intrusion-related rare earth element deposits are presented together in this report because of the spatial, and potentially genetic, association between carbonatite and alkaline rocks. Although these rock types occur together at many locations, carbonatite and peralkaline intrusion-related rare earth element deposits are not generally found together. Carbonatite hosted rare earth element deposits are found throughout the world, but currently only five are being mined for rare earth elements: Bayan Obo, Daluxiang, Maoniuping, and Weishan deposits in China and the Mountain Pass deposit in California, United States. These deposits are enriched in light rare earth elements, including lanthanum, cerium, praseodynium, and neodynium. The principal rare earth element-minerals associated with carbonatites are fluocarbonates (bastnäsite, parisite, and synchysite), hydrated carbonates (ancylite), and phosphates (monazite) with bastnäsite being the primary ore mineral. Calcite and dolomite are the primary gangue minerals. At present, the only rare earth element production from a peralkaline intrusion-related deposit is as a byproduct commodity at the Lovozero deposit in Russia. Important rare earth element minerals found in various deposits include apatite, eudialyte, loparite, gittinsite, xenotime, gadolinite, monazite, bastnäsite, kainosite, mosandrite, britholite, allanite, fergusonite, and zircon, and these minerals tend to be enriched in heavy rare earth elements. Carbonatite and alkaline intrusive complexes are derived from partial melts of mantle material, and neodymium isotopic data are consistent with the rare earth elements being derived from the parental magma. Deposits and these associated rock types tend to occur within stable continental tectonic units, in areas defined as shields, cratons, and crystalline blocks; they are generally associated with intracontinental rift and fault systems. Protracted fractional crystallization of the magma leads to enrichment in rare earth elements and other incompatible elements. Rare earth element mineralization associated with carbonatites can occur as either primary mineral phases or as mineralization associated with late stage orthomagmatic fluids. Rare earth element mineralization associated with alkaline intrusive complexes may occur as primary phases in magmatic layered complexes or as late-stage dikes and veins. The greatest environmental challenges associated with carbonatite and peralkaline intrusion-related rare earth element deposits center on the associated uranium and thorium. Considerable uncertainty exists around the toxicity of rare earth elements and warrants further investigation. The acid-generating potential of carbonatites and peralkaline intrusion-related deposits is low due to the dominance of carbonate minerals in carbonatite deposits, the presence of feldspars and minor calcite within the alkaline intrusion deposits, and only minor quantities of potentially acid-generating sulfides. Therefore, acid-drainage issues are not likely to be a major concern associated with these deposits. Uranium has the potential to be recovered as a byproduct, which would mitigate some of its environmental effects. However, thorium will likely remain a waste-stream product that will require management since progress is not being made towards the development of thorium-based nuclear reactors in the United States or other large scale commercial uses. Because some deposits are rich in fluorine and beryllium, these elements may be of environmental concern in certain locations.

Scientific Investigations Report↗
USGS1959

Radioactive rare-earth deposit at Scrub Oaks mine, Morris County, New Jersey

A deposit of rare-earth minerals in the Scrub Oaks iron mine, Morris County, N. J., was mapped and sampled in 1955. The rare-earth minerals are mainly in coarse-grained magnetite ore and in pegmatite adjacent to it. Discrete bodies of rare-earth-bearing magnetite ore apparently follow the plunge of the main magnetite ore body at the north end of the mine. Radioactivity of the ore containing rare earths is about 0.2 to 0.6 mllliroentgens per hour. The principal minerals of the deposit are quartz, magnetite, hematite, albiteoligoclase, perthite and antiperthite. Xenotime and doverite aggregates and bastnaesite with intermixed leucoxene are the most abundant rare-earth minerals, and zircon, sphene, chevkinite, apatite, and monazite are of minor abundance in the ore. The rare-earth elements are partly differentiated into cerium-rich bastnaesite, chevkinite, and monazite, and yttrium-rich xenotime and doverite. Apatite, zircon, and sphene contain both cerium and yttrium group earths. Eleven samples of radioactive ore and rock average 0.009 percent uranium, 0.062 percent thorium, 1.51 percent combined rare-earth oxides including yttrium oxide and 24.8 percent iron. Scatter diagrams of sample data show a direct correlation between equivalent uranium, uranium, thorium, and combined rare^ earth oxides. Both cerium- and yttrium-group earths are abundant in the rare-earth minerals. Radioactive magnetite ore containing rare-earth minerals probably formed as a variant of the magnetite mineralization that produced the main iron ore of the Scrub Oaks deposit. The rare-earth minerals and the iron ore were deposited contemporaneously. Zircon crystals, probably deposited at the same time, have been determined by the Larsen method to be about 550 to 600 million years old (late Precambrian age). Uranium, thorium, and rare-earth elements are potential byproducts of iron in the coarse-grained magnetite ore.

New Jersey↗
USGS1983

Geology and description of thorium and rare-earth deposits in the southern Bear Lodge Mountains, northeastern Wyoming

The Bear Lodge Mountains are a small northerly trending range approximately 16 km northwest of the Black Hills in the northeast corner of Wyoming. Thorium and rare-earth deposits occur over an area of 16 km 2 in the southern part of these mountains. These deposits occur in the core of the Bear Lodge dome in a large multiple intrusive body made up principally of trachyte and phonolite. Two types of deposits are recognized: disseminated deposits and veins. The disseminated deposits are made up of altered igneous rocks cut by numerous crisscrossing veinlets. The disseminated deposits contain thorium and rare-earth minerals in a matrix consisting principally of potassium feldspar, quartz, and iron and manganese oxides. Total rare-earth content of these deposits is about 27 times that of the thorium content. The general size and shape of the disseminated deposits were outlined by making a radiometric map using a scintillation counter of the entire Bear Lodge core, an area of approximately 30 km 2 . The most favorable part of this area, which was outlined by the 40 countJs (count-per-second) isograd on the radiometric map, was sampled in detail. A total of 341 samples were taken over an area of 10.6 km 2 and analyzed for as many as 60 elements. Rare earths and thorium are the principal commodities of interest in these deposits. Total rare-earth content of these samples ranged from 47 to 27,145 ppm (parts per million), and the thorium content from 9.3 to 990 ppm. The amount of total rare earths of individual samples shows little correlation with that of thorium. Contour maps were constructed using the analytical data for total rare earths, thorium, uranium, and potassium. The total rare-earth and thorium maps can be used to define the size of the deposits based on what cut-off grade may be needed during mining. The size is large as the 2,000 ppm total rare-earth isograd encloses several areas that total 3.22 km 2 in size, and the 200 ppm thorium isograd encloses several areas that total 1.69 km 2 . These deposits could be mined by open pit. The Bear Lodge disseminated deposits have one of the largest resources of both total rare earths and thorium in the United States, and although the grade of both commodities is lower than some other deposits, their large size and relative cheapness of mining make them an important future resource. Vein deposits in the Bear Lodge Mountains include all tabular bodies at least 5 cm thick. Twenty-six veins were noted in this area. These veins are thin and short; the longest vein was traced for only 137 m. Minerals vary greatly in the amount present. Gangue minerals are commonly potassium feldspar, quartz, or cristobalite intermixed with varying amounts of limonite, hematite, and various manganese oxides. Rare earths and thorium occur in the minerals monazite, brockite, and bastnaesite. Thorium content of 35 samples ranged from 0.01 to 1.2 percent, and the total rare-earth content of 21 samples from 0.23 to 9.8 percent. Indicated reserves were calculated to a depth of one-third the exposed length of the vein. Inferred reserves lie in a block surrounding indicated reserves. Indicated reserves of all veins are only 50 t of Th0 2 and 1,360 t of total rare-earth oxides; inferred reserves are 250 t of Th0 2 and 6,810 t of total rare-earth oxides. The Bear Lodge dome, which underlies the greater part of this area, is formed by multiple intrusive bodies of Tertiary age that dome up the surrounding sedimentary rocks. In the southern part of the core, the younger intrusive bodies surround and partly replace a granite of Precambrian age. This granite is approximately 2.6 b.y. old. The sedimentary rocks around the core are (from oldest to youngest): Deadwood Formation of Late Cambrian and Early Ordovician age, Whitewood Limestone of Late Ordovician age, Pahasapa Limestone of Early Mississippian age, Minnelusa Sandstone of Pennsylvanian and Early Permian age, Opeche Formation of Permian age, Minnek

Professional Paper↗
USGS2002

Human impact on the planet: an earth system science perspective and ethical considerations

The modern Earth Narrative, the scientific story of the 4.5 billion-year natural and human history of the Earth, has emerged from the solid foundation of two factual concepts: Deep (or Geologic) Time and Biological Evolution. spread acceptance of the Earth Narrative is critically important as we begin the third millennium, because it provides a clear understanding of the growing impact of human population growth and associated activities on the Earth System, especially the negative impact on Earth?s biosphere. It is important for humans to realize that we are but one of 4,500 species of mammals that exist on Earth and that we are but one species in the estimated 30 to 100 million species that form the complex biosphere. We also need to recognize that all species exist within the physical limits imposed by the geosphere. We are totally dependent on the biosphere for food, oxygen, and other necessities of life. mans are one of the latest results of biological evolution operating over a long period of Geologic Time. We find ourselves on Earth, after 4.5 billion years of Earth history by chance, not by design. Humans have become so successful at modifying their environment that many of the natural limitations on the expansion of populations of our fellow animals have been overcome by technological and cultural innovations. According to Peter Raven, ?Humans, at a current population of 6 billion [expected to nearly double by 2050], are consuming or wasting about 50 percent of the total net biological productivity on land and 50 percent of the available supply of freshwater. The overwhelming and expanding human presence leaves less and less room in the environment for other biota.? st century will be a pivotal time in the fate of Earth?s biosphere. Whereas human modification of the geosphere will slowly recover over time, human changes to the biosphere are a far more consequential matter? extinction of a species is forever! Will humans effectively use our new knowledge of natural and human history to stop further degradation of Earth?s ecosystems and extinction of its biota? The fate of the biosphere, including humanity, depends on a reaffirmation by all humans of all cultures and religions of the global importance of a planet-wide conservation of the Earth?s biotic heritage. For the world?s religions it means elevation of stewardship of the Earth to a moral imperative and a goal of complete preservation of the Earth?s biotic inheritance, one which is based on a Do No Harm ethic.

Open-File Report↗
USGS2014

Multi-temporal mapping of a large, slow-moving earth flow for kinematic interpretation

Periodic movement of large, thick landslides on discrete basal surfaces produces modifications of the topographic surface, creates faults and folds, and influences the locations of springs, ponds, and streams (Baum, et al., 1993; Coe et al., 2009). The geometry of the basal-slip surface, which can be controlled by geological structures (e.g., fold axes, faults, etc.; Revellino et al., 2010; Grelle et al., 2011), and spatial variation in the rate of displacement, are responsible for differential deformation and kinematic segmentation of the landslide body. Thus, large landslides are often composed of several distinct kinematic elements. Each element represents a discrete kinematic domain within the main landslide that is broadly characterized by stretching (extension) of the upper part of the landslide and shortening (compression) near the landslide toe (Baum and Fleming, 1991; Guerriero et al., in review). On the basis of this knowledge, we used photo interpretive and GPS field mapping methods to map structures on the surface of the Montaguto earth flow in the Apennine Mountains of southern Italy at a scale of 1:6,000. (Guerriero et al., 2013a; Fig.1). The earth flow has been periodically active since at least 1954. The most extensive and destructive period of activity began on April 26, 2006, when an estimated 6 million m3 of material mobilized, covering and closing Italian National Road SS90, and damaging residential structures (Guerriero et al., 2013b). Our maps show the distribution and evolution of normal faults, thrust faults, strike-slip faults, flank ridges, and hydrological features at nine different dates (October, 1954; June, 1976; June, 1991; June, 2003; June, 2005; May, 2006; October, 2007; July, 2009; and March , 2010) between 1954 and 2010. Within the earth flow we recognized several kinematic elements and associated structures (Fig.2a). Within each kinematic element (e.g. the earth flow neck; Fig.2b), the flow velocity was highest in the middle, and lowest in the upper and lower parts. As the velocity of movement initiated and increased, stretching of the earth flow body induced the formation of normal faults. Conversely, decreasing velocity and shortening of the earth flow induced the formation of thrust faults. A zone with relatively few structures, bounded by strike-slip faults, was located between stretching and shortening areas. These kinematic elements indicate that the overall earth flow was actually composed of numerous linked internal earth flows, with each internal flow having a distinct pattern of structures representative of stretching and shortening (Guerriero et al., in review). These observations indicated that the spatial variation in movement velocity associated with each internal earth flow, mimicked the pattern of movement for the overall earth flow. That is, the earth flow displayed a self-similar pattern at different scales. Furthermore, the presence of other structures such as back-tilted surfaces, flank-ridges, and hydrological elements provide specific information about the shape of the basal topographic surface. Our multi-temporal maps provided a basis for interpretation of the long-term kinematic evolution of the earth flow and the influence of the basal-slip surface on the earth flow movement. Our maps showed that main faults remained stationary through time, despite extensive mobilization and movement of material. This observation indicated that the slip-surface has remained relatively stationary since at least 1954.

Conference Paper↗
USGS2024

Conventional rare earth element mineral deposits: The global landscape

Four conventional mineral deposit types—carbonatite, alkaline igneous, heavy mineral sand, and regolith-hosted ion-adsorption clay deposits—currently supply global markets with the rare earth elements (REEs) and rare earth oxides (REOs) necessary to meet the technological needs of global communities. The unique properties of REEs make them useful in a wide variety of applications, such as alloys, batteries, catalysts, magnets, phosphors, and polishing compounds. Rare earth element minerals are complex in both composition and structure. Carbonate, oxide, silicate, and phosphate-type minerals contain highly variable amounts of rare earths. Most rare earth-bearing minerals contain mainly lighter rare earths, a mixture of all the rare earths, or only the heavier rare earths. Diverse technological applications require the full range of light, middle, and heavy rare earths. The production of these elements, in particular the heavy rare earths, remains highly dependent on deposits from China. Diversification of rare earth supply chains is contingent on expanded knowledge of globally distributed resources and an understanding of the degree to which those resources have been explored and evaluated. The knowledge of tectonic setting, typical rock associations, deposit morphology, and deposit genesis has led to the discovery of many conventional-type rare earth deposit types. Recent developments are anticipated to result in further discoveries that have the potential to meet the ever-expanding applications of REEs and REOs to address modern societal needs.

Book chapter↗
USGS2011

China's rare-earth industry

Introduction China's dominant position as the producer of over 95 percent of the world output of rare-earth minerals and rapid increases in the consumption of rare earths owing to the emergence of new clean-energy and defense-related technologies, combined with China's decisions to restrict exports of rare earths, have resulted in heightened concerns about the future availability of rare earths. As a result, industrial countries such as Japan, the United States, and countries of the European Union face tighter supplies and higher prices for rare earths. This paper briefly reviews China's rare-earth production, consumption, and reserves and the important policies and regulations regarding the production and trade of rare earths, including recently announced export quotas. The 15 lanthanide elements-lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium (atomic numbers 57-71)-were originally known as the rare earths from their occurrence in oxides mixtures. Recently, some researchers have included two other elements-scandium and yttrium-in their discussion of rare earths. Yttrium (atomic number 39), which lies above lanthanum in transition group III of the periodic table and has a similar 3+ ion with a noble gas core, has both atomic and ionic radii similar in size to those of terbium and dysprosium and is generally found in nature with lanthanides. Scandium (atomic number 21) has a smaller ionic radius than yttrium and the lanthanides, and its chemical behavior is intermediate between that of aluminum and the lanthanides. It is found in nature with the lanthanides and yttrium. Rare earths are used widely in high-technology and clean-energy products because they impart special properties of magnetism, luminescence, and strength. Rare earths are also used in weapon systems to obtain the same properties.

Open-File Report↗
USGS1979

Use of U.S. Geological Survey earth-science products by selected regional agencies in the San Francisco Bay region, California

An inventory of the use of U.S. Geological Survey (USGS) products in studies, plans, implementation, and other planning activities was made for seven selected regional agencies in the San Francisco Bay region -- a region of over five million people. This inventory was designed to determine and document the use of over 100 earth-science products prepared as a part of the San Francisco Bay Region Environment and Resources Planning Study (SFBRS). The inventory showed that: (1) all seven agencies have staff members who are familiar with SFBRS products and make frequent use of them; (2) all seven agencies have prepared planning documents citing SFBRS products; (3) the types of planning applications most often indicated were water-quality and physical resources studies, potential site evaluation, and general reference; (4) almost 80 percent of the over 100 SFBRS products were used at least once, and eleven of the products were used 20 or more times each for various regional planning activities; and (5) at least 46 other USGS products were also used for various regional planning activities. During the inventory, over 50 regional agency. officials, employees, and consultants were interviewed and asked -- among other things -- to indicate any problems they had noted in the use of the SFBRS products, to suggest improvements, and to identify any additional earth-science information needed or desired. The responses showed that: (1) the scales commonly used for "work" maps were 1:62,500 or larger, and for "implementation" maps were 1:24,000 or larger; (2) two agencies have a geologist on their planning staff, others have staff members with training or experience in earth-science or engineering, and all had the benefit of geotechnical services from outside their agency; (3) all seven agencies experienced some problems in using the products, primarily because the scale was too small or the detail not great enough; (4) all seven agencies expressed interest in the topical interpretive reports in preparation and a need or desire for additional earth-science, engineering, or other related information; (5) six of the seven agencies suggested specific improvements to future products -- primarily larger scale or more detail and less technical or more interpretive information; and (6) all seven agencies received educational, advisory or review services from USGS personnel. Fifteen selected examples of the application of SFBRS products to various regional planning activities are discussed and illustrated. These examples include six planning studies, five plans, two implementation activities, and two other types of activities. From the inventory and responses to the interviews, it is concluded that the selected regional agencies in the bay region are familiar with, make frequent use of, and will continue to use SFBRS products for a wide range of regional planning activities. Suggestions to ensure more effective use of earth-science information in the future include: (1) monitoring and analyzing new State and Federal laws or regulations and emerging critical issues so as to anticipate and respond to regional earth-science information needs; (2) creating a users advisory committee to help identify critical issues and needs; (3) providing engineering interpretations and land- and water-use capability ratings to make earth-science information more readily usable; (4) giving priority to areas impacted by development; (5) providing earth-science information at the larger scale and greater detail commonly used and needed by regional agencies; (6) releasing earth-science information faster and according to a formal distribution pattern; and (7) providing educational, advisory, and review services in connection with any earth-science information designed for planners and decisionmakers.

California↗
USGS2012

Byproduct metals and rare-earth elements used in the production of light-emitting diodes—Overview of principal sources of supply and material requirements for selected markets

The use of light-emitting diodes (LEDs) is expanding because of environmental issues and the efficiency and cost savings achieved compared with use of traditional incandescent lighting. The longer life and reduced power consumption of some LEDs have led to annual energy savings, reduced maintenance costs, and lower emissions of carbon dioxide, sulfur dioxide, and nitrogen oxides from powerplants because of the resulting decrease in energy consumption required for lighting applications when LEDs are used to replace less-energy-efficient sources. Metals such as arsenic, gallium, indium, and the rare-earth elements (REEs) cerium, europium, gadolinium, lanthanum, terbium, and yttrium are important mineral materials used in LED semiconductor technology. Most of the world's supply of these materials is produced as byproducts from the production of aluminum, copper, lead, and zinc. Most of the rare earths required for LED production in 2011 came from China, and most LED production facilities were located in Asia. The LED manufacturing process is complex and is undergoing much change with the growth of the industry and the changes in demand patterns of associated commodities. In many respects, the continued growth of the LED industry, particularly in the general lighting sector, is tied to its ability to increase LED efficiency and color uniformity while decreasing the costs of producing, purchasing, and operating LEDs. Research is supported by governments of China, the European Union, Japan, the Republic of Korea, and the United States. Because of the volume of ongoing research in this sector, it is likely that the material requirements of future LEDs may be quite different than LEDs currently (2011) in use as industry attempts to cut costs by reducing material requirements of expensive heavy rare-earth phosphors and increasing the sizes of wafers for economies of scale. Improved LED performance will allow customers to reduce the number of LEDs in automotive, electronic, and lighting applications, which could reduce the overall demand for material components. Non-Chinese sources for rare earths are being developed, and some of these new sources are likely to be operational in time to meet increasing demand for rare earths from the LED sector. Because most LED component production and manufacturing occurs in Asia and many LED producers have established supply contracts with Chinese producers of rare earths, a significant amount of the metallic gallium, indium, and the rare earths used for LED production will likely continue to come from Chinese sources at least for the next 5 years; however, a greater amount of these materials are now being processed in Japan, the Republic of Korea, and Taiwan. As non-Chinese sources of rare earths come into production, these new mines are likely to be sources of light REEs, but China will likely remain the leading source of supply for the heavy REEs suitable for use as LED dopants and phosphors at least for the next few years. Increased research in the development of phosphors that use smaller amounts of or different REEs is intended to reduce dependence on rare earths from China. Supply disruption of rare earths and other specialty metals could take place if China's specialty metal exports are redirected to domestic markets. The cost of recovery is high and the lifespan for LEDs is comparatively long; thus, the LED waste volume was low in 2010, and few LEDs were recycled. The minute metal content of LEDs leads to a high cost for recovery, so recycling of LEDs outside of electronic waste is unlikely in the near term, although some LED producers are evaluating recycling options. Recycling of metals from LEDs in electronic waste is possible if the costs of recovering metals are justified by demand and metal prices.

Scientific Investigations Report↗
USGS2018

Can the earth be dated from decay of its magnetic field?.

Thomas G. Barnes, Emeritus Professor of Physics at the University of Texas, El Paso, and a creationist, argues that the geomagnetic field was created by unknown processes at the time of creation of the earth and has been decaying irreversibly and exponentially, with a half-life of about 1400 years, since then. He calculates that the field would have been impossibly large in 8000 B.C. and concludes that the earth, therefore, is less than 10,000 years old. He denies that the earth's field has reversed polarity in the past, and attempts to refute the dynamo theory of the origin of the field. Barnes' arguments and conclusions are commonly cited in creationist literature as definitive proof that the earth is very young. Barnes is wrong, and has ignored or misrepresented much of the data on the earth's magnetic field. Barnes calculations are based on observatory measurements showing that the earth's dipole field strength has decreased since 1835. But these same measurements also show a corresponding increase in the strength of the nondipole field so that the total field energy external to the core has remained about constant. Paleomagnetic evidence shows that the earth's field has existed for more than three billion years, and that the dipole field both fluctuates in strength and irregularly reverses polarity. The earth's field is generated by a fluid dynamo in the iron-nickel core; all of the elements necessary for a dynamo, including fluid motion and energy sources, are present. Contrary to Barnes' assertions, there are no theoretical reasons why a dynamo cannot exist in the earth. There are no properties of the magnetid field that can be used to place an upper limit on the earth's age.

Journal of Geological Education↗
USGS1997

What a = 1/298 and C/Ma 2 = 0.333 really tell us about the Earth

The discussion in the several versions of The Earth by Jeffreys (third edition, 1952, for example) [1] relative to the ellipticity of the Earth does not demonstrate, as generally believed, that the Earth has the shape of a rotating liquid. His development in conjunction with the work of H. Lamb (1945) [2] shows unequivocally that the Earth is much less oblate than required if it were behaving as a liquid mass. It is not true that the observations of Bouguer in the late 1700's regarding the actual ellipticity of the Earth demonstrated the liquidity of the Earth with mass concentrated towards the center. In fact, proper interpretation of his data would have shown that the Earth's ellipticity results from its great strength, not its weakness. Data available today establish that great strength resides in the lower mantle and has in all probability resided there from the time of the Earth's origin. This strength results in the need for reinterpretation of Earth behavior and operative processes.

Izvestiya, Physics of the Solid Earth↗
USGS1958

Biogeochemistry of the rare-earth elements with particular reference to hickory trees

Hickory trees concentrate the rare-earth elements in their leaves to a phenomenal degree and may contain as much as 2300 p.p.m. of total rare earths based on the dry weight of the leaves. The average proportions of the individual elements (atomic percent of the total rare-earth elements) in the leaves are: Y 36, La 16, Ce 14, Pr 2, Nd 20, Sm 1, Eu 0.7, Gd 3, Tb 0.6, Dy 3, Ho 0.7, Er 2, Tm 0.2, Yb 1, and Lu 0.2. The similarity in the proportions of the rare-earth elements in the leaves and in the exchange complex of the soil on which the hickory trees grow indicates that the trees do not fractionate the rare earths appreciably. The variation of the rare-earth elements in the leaves and soils can be explained generally in terms of the relative abundance of the cerium group and the yttrium group, except for the element cerium. The large fluctuations in the proportion of cerium [Ce/(La + Nd) atomic ratios of 0.16 to 0.86] correlate with oxidation-reduction conditions in the soil profile. The substitution of dilute H 2 SO 3 for dilute HC1 in the determination of available rare-earth elements brings about a large increase in the proportion of cerium that is extracted from an oxygenated subsoil. These relationships strongly suggest that quadrivalent cerium is present in oxygenated subsoil and is less available to plants than the other rare-earth elements that do not undergo such a change in valence. A few parts per billion of rare-earth elements have been detected in two samples of ground water.

Geochimica et Cosmochimica Acta↗
USGS2024

The early Earth as an analogue for exoplanetary biogeochemistry

Planet Earth has evolved over the past 4.5 billion years from an entirely anoxic planet with possibly a different tectonic regime to the oxygenated world with horizontal plate tectonics that we know today. For most of this time, Earth has been inhabited by a purely microbial biosphere albeit with seemingly increasing complexity over time. A rich record of this geobiological evolution over most of Earth’s history thus provides insights into the remote detectability of microbial life under a variety of planetary conditions. Here we leverage Earth’s geobiological record with the aim of (a) illustrating the current state of knowledge and key knowledge gaps about the early Earth as a reference point in exoplanet science research; (b) compiling biotic and abiotic mechanisms that controlled the evolution of the atmosphere over time; and (c) reviewing current constraints on the detectability of Earth’s early biosphere with state-of-the-art telescope technology. We highlight that life may have originated on a planet with a different (stagnant lid) tectonic regime and strong hydrothermal activity, and under these conditions, biogenic CH 4 gas was perhaps the most detectable atmospheric biosignature. Oxygenic photosynthesis, which is responsible for essentially all O 2 gas in the modern atmosphere, appears to have emerged concurrently with the establishment of modern plate tectonics and the emergence of continental crust, but O 2 accumulation to modern levels only occurred late in Earth’s history, perhaps tied to the rise of land plants. Nutrient limitation in anoxic oceans, promoted by hydrothermal Fe fluxes, may have limited biological productivity and O 2 production. N 2 O is an alternative biosignature that was perhaps significant on the redox-stratified Proterozoic Earth. We conclude that the detectability of atmospheric biosignatures on Earth was not only dependent on biological evolution but also strongly controlled by the evolving tectonic context.

Reviews in Mineralogy and Geochemistry↗