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Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

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At least 163 records · Page 9Linked to original sources
USGS1999

Crystal growth mechanisms in miarolitic cavities in the Lake George ring complex and vicinity, Colorado

The Crystal Peak area of the Pikes Peak batholith, near Lake George in central Colorado, is world-renowned for its crystals of amazonite (the blue-green variety of microcline) and smoky quartz. Such crystals, collected from individual miarolitic pegmatites, have a remakably small variation in crystal size within each pegmatite, and the shapes of plots of their crystal size distributions (CSDs) are invariably lognormal or close to lognormal in all cases. These observations are explained by a crystal growth mechanism that was governed initially by surface-controlled kinetics, during which crystals tended to grow larger in proportion to their size, thereby establishing lognormal CSDs. Surface-controlled growth was followed by longer periods of supply controlled growth, during which growth rate was predominantly size-independent, consequently preserving the lognormal shapes of the CSDs and the small size variation. The change from surface- to supply controlled growth kinetics may have resulted from an increasing demand for nutrients that exceeded diffusion limitations of the system. The proposed model for crystal growth in this locality appears to be common in the geologic record, and can be used with other information, such as isotopic data, to deduce physico-chemical conditions during crystal formation.

American Mineralogist↗
USGS2018

Identifying major avalanche years from a regional tree-ring based avalanche chronology for the U.S. Northern Rocky Mountains

Avalanches not only pose a major hazard to people and infrastructure, but also act as an important ecological disturbance. In many mountainous regions in North America, including areas with existing transportation corridors, reliable and consistent avalanche records are sparse or non-existent. Thus, inferring long-term avalanche patterns and associated contributory climate and weather factors requires the use of dendrochronological methods...

Conference Paper↗
USGS2023

Ring-necked Pheasant brood habitat selection and movements in an intensive agricultural landscape

Management of row crops can greatly influence wildlife populations in an agriculturally intensive landscape. Many upland gamebird populations, including Phasianus colchicus L. (Ringnecked Pheasant; hereafter pheasant) are experiencing contemporary population declines in such landscapes throughout the Midwest United States. Reduced availability of quality brood habitat may be a factor in these declines. Alternative practices, such as spring cover crops, may increase brood survival and benefit local pheasant populations. Our objectives were to follow radio-tagged females and assess pheasant brood 1) movements among available habitat patches within landscapes including spring cover crops and Conservation Reserve Program (CRP) fields, 2) relative use of available cover types within a landscape, 3) selection of vegetation structure, vegetation composition, and invertebrate community structure by brood-rearing hens in landscapes dominated by row-crop agriculture, and 4) survival rates. Broods were found primarily in grassy areas (native grass, pasture, train track right-of-way, and grass strips) and spring cover crop fields even though cover crops were the least common cover type in all study areas. Brood movements were limited with broods staying near nest locations for 30 days after hatch. Though movements were small, broods were found in multiple cover types, averaging 2.8 out of 6 available cover types. There was no difference between used and random locations for invertebrate metrics including total counts, biomass, and richness; order-specific biomass; and order-specific counts. Visual obstruction and vegetation composition were similar between used and random locations. Across our study sites, we found little support for point-site selection (i.e., within-patch 4th order selection) but significant support for patch-site selection by female pheasants attending broods. Spring cover crops (<5%) and CRP (<15%) comprised a small percentage of the landscape area, but were selected by females attending broods as each contained approximately 25% of brood locations. Apparent survival of pheasant broods was low compared to other studies. Female pheasants selected for spring cover crops and CRP when attending broods, both are alternatives to current row-crop farming practices. As pheasants continue to respond to changes in western Kansas landscapes, homogeneity of cover types found in agricultural landscapes can be detrimental if practices continue to shift from quality pheasant habitat but can be advantageous if practices shift towards favorable management practices.

Kansas↗
USGS2009

Multiple dendrochronological responses to the eruption of Cinder Cone, Lassen Volcanic National Park, California

Two dendrochronological properties – ring width and ring chemistry – were investigated in trees near Cinder Cone in Lassen Volcanic National Park, northeastern California, for the purpose of re-evaluating the date of its eruption. Cinder Cone is thought to have erupted in AD 1666 based on ring-width evidence, but interpreting ring-width changes alone is not straightforward because many forest disturbances can cause changes in ring width. Old Jeffrey pines growing in Cinder Cone tephra and elsewhere for control comparison were sampled. Trees growing in tephra show synchronous ring-width changes at AD 1666, but this ring-width signal could be considered ambiguous for dating the eruption because changes in ring width can be caused by other events. Trees growing in tephra also show changes in ring phosphorus, sulfur, and sodium during the late 1660s, but inter-tree variability in dendrochemical signals makes dating the eruption from ring chemistry alone difficult. The combination of dendrochemistry and ring-width signals improves confidence in dating the eruption of Cinder Cone over the analysis of just one ring-growth property. These results are similar to another case study using dendrochronology of ring width and ring chemistry at Parícutin, Michoacán, Mexico, a cinder cone that erupted beginning in 1943. In both cases, combining analysis with ring width and ring chemistry improved confidence in the dendro-dating of the eruptions.

California↗
USGS1963

Some climatic indicators in the period A.D. 1200-1400 in New Mexico

Three centuries before Columbus landed in America, the alluvial valleys of the south-western United States teemed with activity. The indigenous peoples had been building for 300 years a culture centred around community life based on flood-water farming and on hunting. A large number of pueblos had developed on sites earlier occupied by pit-house people. Community organization had brought advances in the ceramic and decorative arts, and changes in these artistic activities were sufficiently rapid that accurate chronologies have become available through the work of archaeologists during the twentieth century. These chronologies were at first unrelated to absolute dates, but the excavations of the 1920s at Chaco Canyon (New Mexico) provided the materials through which absolute dates could be established. This was accomplished by matching the changes in tree-ring width backward in time from living trees through successively older samples. Trees overlapping in age provided, by unique successions of distinctive tree-ring widths, a calendar by which individual logs could be dated. Beams found in the excavations at Chaco Canyon gave the first material by which the cultural developments culminating about A.D. 1300 could be dated. As a result of the time sequence provided by the tree-ring calendar, the dates within which different pottery types were developed could be accurately established. The dates of pottery types have been checked at a sufficiently large number of sites throughout the south-western United States that absolute dating of a large number of distinctive patterns can be considered unassailable. The sequence of tree-ring widths gives some climatic indications of great interest both to archaeologists and to climatologists. A relatively large number of logs spanning the period from A.D. 1200 to 1300 and, in particular, the years between 1276 and 1299, indicate that this period was generally characterized by smaller tree-ring widths than in the centuries immediately before and after. As a first approximation, the hundred years of narrow tree-ring widths were interpreted as a time of relative aridity, and have been referred to as the “Pueblo Drought”. More recent studies of tree-ring widths using sophisticated statistical techniques have thrown some doubts on any direct correlation of tree-ring widths with rainfall. Such doubts have been put forward before by Glock (1955) whose studies have been aimed at separating the various effects of seasonal occurrence of precipitation, the amount falling in various seasons, and other climatic factors in their relative influence on tree-ring widths. At present, then, tree-ring widths may be considered more satisfactory for reading chronology than for reading climate. It is this concern about direct correlation of tree-ring width with climate that led to initiation of the present study. This work is a preliminary attempt to obtain independent evidence from pollen concerning the probable nature of the vegetation and thus the climate in a period known to be characterized by narrow tree rings.

New Mexico↗
USGS2011

Characterizing near-surface CO2 conditions before injection - Perspectives from a CCS project in the Illinois Basin, USA

The Midwest Geological Sequestration Consortium is conducting a large-scale carbon capture and storage (CCS) project in Decatur, Illinois, USA to demonstrate the ability of a deep saline formation to store one million tonnes of carbon dioxide (CO 2 ) from an ethanol facility. Beginning in early 2011, CO 2 will be injected at a rate of 1,000 tonnes/day for three years into the Mount Simon Sandstone at a depth of approximately 2,100 meters. An extensive Monitoring, Verification, and Accounting (MVA) program has been undertaken for the Illinois Basin Decatur Project (IBDP) and is focused on the 0.65 km2 project site. Goals include establishing baseline conditions to evaluate potential impacts from CO 2 injection, demonstrating that project activities are protective of human health and the environment, and providing an accurate accounting of stored CO 2 . MVA efforts are being conducted pre-, during, and post- CO 2 injection. Soil and net CO 2 flux monitoring has been conducted for more than one year to characterize near-surface CO 2 conditions. More than 2,200 soil CO 2 flux measurements have been manually collected from a network of 118 soil rings since June 2009. Three ring types have been evaluated to determine which type may be the most effective in detecting potential CO 2 leakage. Bare soil, shallow-depth rings were driven 8 cm into the ground and were prepared to minimize surface vegetation in and near the rings. Bare soil, deep-depth rings were prepared similarly, but were driven 46 cm. Natural-vegetation, shallow-depth rings were driven 8 cm and are most representative of typical vegetation conditions. Bare-soil, shallow-depth rings had the smallest observed mean flux (1.78 μmol m −2 s −1 ) versus natural-vegetation, shallow-depth rings (3.38 μmol m −2 s −1 ). Current data suggest bare ring types would be more sensitive to small CO 2 leak signatures than natural ring types because of higher signal to noise ratios. An eddy covariance (EC) system has been in use since June 2009. Baseline data from EC monitoring is being used to characterize pre-injection conditions, and may then be used to detect changes in net exchange CO 2 fluxes (Fc) that could be the result of CO 2 leakage into the near-surface environment during or following injection. When injection at IBDP begins, soil and net CO 2 monitoring efforts will have established a baseline of near-surface conditions that will be important to help demonstrate the effectiveness of storage activities.

Illinois↗
USGS2020

Dendrochronology of a rare long-lived mediterranean shrub

Ceanothus verrucosus (CEVE) is a globally rare, long-lived, chaparral shrub endemic to coastal southern California (CA) and northern Mexico. There is concern for CEVE persistence because of habitat loss, fire, and climate change, yet little is known about basic features of the plant, including whether it contains annual rings, plant age, and climate–growth response. Growth-ring analysis was challenging because of semi-ring-porous structure, false, and missing rings. We successfully crossdated CEVE annual rings, primarily from Cabrillo National Monument, CA, using a nearby Pinus torreyana chronology. The oldest living individual had 116 rings; the oldest inner-ring date was 1873; and most of the plants established between 1894 and 1905, all older than previous estimates. CEVE mortality occurred during a dry period from the late 1940s through the early 1960s. Correlations between age and stem measurements were weak to moderate (r = 0.10 to 0.56) posing challenges for field-based estimates of plant ages, which are important for population modeling. Variability in CEVE ring width had a strong positive correlation with prior cool-season (October–April) precipitation, yet 2- to 7-day warm-season precipitation events were recorded as rare false rings in multiple years, indicating extreme plasticity in cambial phenology and growth response to moisture.

California↗
USGS1983

Evidence of floods on the Potomac River from anatomical abnormalities in the wood of flood-plain trees

Ash trees along the Potomac River flood plain near Washington, D.C., were studied to determine changes in wood anatomy related to flood damage, and anomalous growth was compared to flood records for April 15 to August 31, 1930-79. Collectively, anatomical evidence was detected for 33 of the 34 growing-season floods during the study period. Evidence of 12 floods prior to 1930 was also noted, including catastrophic ones in 1889 and 1924. Trees damaged after the transition from earlywood to latewood growth typically formed ' flood rings ' of enlarged vessels within the latewood zone. Trees damaged near the beginning of the growth year developed flood rings within, or contiguous with, the earlywood. Both patterns are assumed to have developed when flood-damaged trees produced a second crop of leaves. Trees damaged by high-magnitude floods developed well formed flood rings along the entire height and around the entire circumference of the stem. Small floods were generally associated wtih diffuse or discontinuous anomalies restricted to stem apices. Frequency of flood rings was positively related to flood magnitude, and time of flood generation during the tree-growth season was estimated from the radial position of anomalous growth relative to annual ring width. Reconstructing tree heights in a year of flood-ring formation gives a minimum stage estimate along local stream reaches. Some trees provided evidence of numerous floods. Those with the greatest number of flood rings grew on frequently flooded surfaces subject to flood-flow velocities of at least 1 m/s, and more typically greater than 2 m/s. Tree size, more than age, was related to flood-ring formation. Trees kept small by frequent flood damage had more flood rings than taller trees of comparable age. (USGS)

Professional Paper↗