Plume dynamics, thermal energy and long-distance transport of vulcanian eruption clouds from Augustine Volcano, Alaska     

Juergen Kienle  Glenn E. Shaw 《Journal of Volcanology and Geothermal Research》1979,6(1-2)

Augustine, an island volcano in Lower Cook Inlet, southern Alaska, erupted in January, 1976, after 12 years of dormancy. By April, when the eruptions ended, a new lava dome had been extruded into the summit crater and about 0.1 km³ of pyroclastics had been deposited on the island, mainly as pyroclastic debris avalanches and pumice flows. The ventclearing phase in January was highly explosive and we have been able to document 13 major vulcanian eruptions.The timing, thermal energy, mass loading of fine particles and the horizontal dispersion of these eruption clouds were determined from radar measurements of cloud height, reports of pilots flying in plumes, satellite photography, seismic records and infrasonic detection of air waves. A lower estimate of the mass of fine (r < 68 μm) particles injected into the troposphere from the 13 main eruptions in January is 5.5–18 × 10¹² g. The corresponding mass loading of fine particles within individual eruption clouds is 0.3–1 g m⁻³. We calculated thermal energies of 4 × 10¹⁴ to 35 × 10¹⁴ J for individual eruptions by applying convective plume rise theory to observed cloud heights and seismically determined eruption durations. This energy range compares favorably with the 4–16 × 10¹⁴ J of thermal energy, calculated from the cooling of juvenile material contained in a typical eruption cloud.The vulcanian eruption clouds stayed intact for at least 700 km downwind. Satellite images in both visible and infrared wavebands, showing the Gulf of Alaska just after sunrise on January 23, reveal a series of puffs strung out downwind from the volcano, 20–30 km in diameter and with their tops at altitudes of about 8 km, overlying a continuous plume at altitude 4 km. Each puff corresponded to a seismically and infrasonically timed eruption. A substantial portion of the material injected into the atmosphere between January 22 and 25 was rapidly transported by the subpolar jet stream through southwestern Canada and the western United States, then northeast across the States into the Atlantic. The clouds were observed passing over Tucson, Arizona, on January 25 at an elevation of 7 km.Several of the eruptions penetrated into the stratosphere. Sun photometer measurements, taken at Mauna Loa, Hawaii, six weeks after the eruption, showed an increased stratospheric optical thickness of 0.01 (wavelength 0.5 μm), which decayed in about 5 months. The maximum column mass loading of the veil was 4–10 × 10⁻⁷ g cm⁻². The mass of the veil, spread-ever a fourth of the earth's surface, is 10 to 100 times larger than can be accounted for by assuming that injected ash and converted sulfate particles from the 13 main Augustine eruptions are the only components contributing to the stratospheric turbidity observed at Mauna Loa.  相似文献   

Some aspects of vortices in rotating stratified fluids     

Glenn J. Shutts  Alan J. Thorpe 《Pure and Applied Geophysics》1978,116(6):993-1006

Summary Ideas concerning the overturning of unstably stratified, rotating fluids are explored using potential vorticity.A set of equations governing axi-symmetric flow in a quasi-Boussinesq system are found based on the gradient wind approximation, and a transformation analogous to that developed byHoskins [6] is used.The time-development of a linear, thermally unstable vortex under the action of Ekman pumping is studied with these equations. The changing radial scale during amplification of the vortex is well represented.Finally, some exact steady vortex states for stably stratified fluids are found and their possible relevance to atmospheric vortices is discussed.  相似文献   

Seasonal and environmental variations in sediment accretion in a Long Island salt marsh     

Glenn A. Richard 《Estuaries and Coasts》1978,1(1):29-35

Flax Pond is a small (0.5 km²) salt marsh on the north shore of Long Island, New York. Two 1 m² plots within each of the following environments were covered with a marker layer of either brick dust or aluminum glitter: 1) bare mud flats; 2) areas newly colonized by Spartina alterniflora; and 3) high intertidal. S. alterniflora peat surfaces. Monthly cores revealed the amount of sediment that accumulated since placement of the marker. Accretion rates from October, 1974 to February, 1976 were as follows: bare mud flats ?20.5 to 45.5 mm/yr; recently vegetated mud flats ?9.5 to 37.0 mm/yr; and high intertidal peat surfaces ?2.0 to 4.25 mm/yr. Sedimentation rates decrease with increasing elevation because of the reduced tidal submergence time and decreased height of the overlying water column. In areas of low elevation, ice and storms cause either erosion or a reduced rate of accretion during the winter months. The average mud accretion rate over the past 173 years is 3.4 mm/yr. Differences between the short-term rate and the long-term rate indicate substantial annual variation in the accumulation of mud in salt marshes. Short-term rates of peat accretion are similar to long-term estimates, indicating that rates of peat accretion are relatively constant over long intervals.  相似文献   

Uranium series dating of stalagmites from Blanchard Springs Caverns,U.S.A.     

Glenn M. Thompson  David N. Lumsden  Raymond L. Walker  Joel A. Carter 《Geochimica et cosmochimica acta》1975,39(9):1211-1218

Because stalagmites are enriched in ²³⁴U beyond the equilibrium value at the time of deposition, they are potentially datable by measuring their progress toward equilibrium. Procedures for uranium-thorium and uranium disequilibrium dating of speleothems were developed, making use of alpha spectrometry for thorium determinations and mass spectrometry for uranium determinations. The stalagmites tested were generally beyond the age range of the U-Th age dating method and, as a result, ²³⁴U/²³⁸U ratios provided the most useful dating technique. The estimated age range for a stalagmite from Blanchard Springs is 135,000 to 785,000 years BP with an interval of slow or suspended growth from about 320,000 to 570,000 years BP.  相似文献   

HYDRAULIC FRACTURING OF CRYSTALLINE ROCKS STIMULATES YIELD OF TWO TEST WELLS DRILLED IN NEW HAMPSHIRE     

Glenn W. Stewart 《Ground water》1974,12(1):46-47

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X-ray K-edge absorption spectra of Fe minerals and model compounds: Near-edge structure   总被引：1，自引：0，他引：1  

Glenn A. Waychunas  Michael J. Apted  Gordon E. Brown Jr. 《Physics and Chemistry of Minerals》1983,10(1):1-9

Synchrotron radiation has been used to collect high-resolution Fe K absorption near-edge spectra of a suite of Fe minerals and compounds having a range of Fe environments. These spectra, along with those of previous workers, indicate that the number, position, and intensity of near-edge features are characteristic of Fe valence and general site geometry. For example, the crest of the K-edge for Fe²⁺ in a six-coordinated site in the oxides studied is about 3 eV lower in energy than that for Fe³⁺ in a similar site. The K-edge crest for Fe³⁺ in a four-coordinated site is 1 to 2 eV lower than for Fe³⁺ in a regular site. The shape of the edge crest is sensitive to the details of first-neighbor bonding distances, tending to be broader in species with irregular Fe sites and varying in energy according to the average bond length. Comparison with Ca²⁺ and Zn²⁺ spectra from the literature is made and the applicability and utility of edge measurements discussed.  相似文献   

Late Holocene sea-level changes and isostatic crustal movements in Atlantic Canada     

W. Roland Gehrels  Glenn A. Milne  Jason R. Kirby  R. Timothy Patterson  D.F.Daniel F. Belknap 《Quaternary International》2004,120(1):79

It has long been recognised that sea levels along the shores of Atlantic Canada have been rising rapidly during the Holocene in response to isostatic crustal movements. New sea-level data for the Bay of Fundy coast of southern New Brunswick (Little Dipper Harbour) and the Atlantic coast of Nova Scotia (Chezzetcook Inlet) show that late Holocene average rates of sea-level rise in these areas have been 1.0 and 2.5 m per 1000 yr, respectively. Numerical model calculations suggest that the high rates of sea-level rise are due to crustal subsidence produced by the combined effects of Laurentide ice loading (forebulge collapse) and ocean loading of the Scotian shelf. Although ice loading is the dominant contributor to the regional sea-level pattern, ocean loading is also important, contributing up to 40% of the total crustal subsidence in some areas. Tide gauges record rates of sea-level rise during the 20^th century that are 0.7–1.9 mm/yr higher than late Holocene trends, with the highest residuals occurring in the Bay of Fundy.  相似文献   

Geomicrobiology of Blood Falls: An Iron-Rich Saline Discharge at the Terminus of the Taylor Glacier, Antarctica   总被引：1，自引：0，他引：1  

Jill A. Mikucki  Christine M. Foreman  Birgit Sattler  W. Berry Lyons  John C. Priscu 《Aquatic Geochemistry》2004,10(3-4):199-220

Blood Falls, a saline subglacial discharge from the Taylor Glacier, Antarctica provides an example of the diverse physical and chemical niches available for life in the polar desert of the McMurdo Dry Valleys. Geochemical analysis of Blood Falls outflow resembles concentrated seawater remnant from the Pliocene intrusion of marine waters combined with products of weathering. The result is an iron-rich, salty seep at the terminus of Taylor Glacier, which is subject to episodic releases into permanently ice-covered Lake Bonney. Blood Falls influences thegeochemistry of Lake Bonney, and provides organic carbon and viable microbes to the lakesystem. Here we present the first data on the geobiology of Blood Falls and relate it totheevolutionary history of this unique environment. The novel geological evolution of thissubglacial environment makes Blood Falls an important site for the study of metabolic strategiesin subglacial environments and the impact of subglacial efflux on associated lake ecosystems.  相似文献   

Mineral/melt partitioning of trace elements during hydrous peridotite partial melting   总被引：6，自引：4，他引：2  

Glenn?A.?GaetaniEmail author  Adam?J.?R.?Kent  Timothy?L.?Grove  Ian?D.?Hutcheon  Edward?M.?Stolper 《Contributions to Mineralogy and Petrology》2003,145(4):391-405

This experimental study examines the mineral/melt partitioning of incompatible trace elements among high-Ca clinopyroxene, garnet, and hydrous silicate melt at upper mantle pressure and temperature conditions. Experiments were performed at pressures of 1.2 and 1.6 GPa and temperatures of 1,185 to 1,370 °C. Experimentally produced silicate melts contain up to 6.3 wt% dissolved H ₂O, and are saturated with an upper mantle peridotite mineral assemblage of olivine+orthopyroxene+clinopyroxene+spinel or garnet. Clinopyroxene/melt and garnet/melt partition coefficients were measured for Li, B, K, Sr, Y, Zr, Nb, and select rare earth elements by secondary ion mass spectrometry. A comparison of our experimental results for trivalent cations (REEs and Y) with the results from calculations carried out using the Wood-Blundy partitioning model indicates that H ₂O dissolved in the silicate melt has a discernible effect on trace element partitioning. Experiments carried out at 1.2 GPa, 1,315 °C and 1.6 GPa, 1,370 °C produced clinopyroxene containing 15.0 and 13.9 wt% CaO, respectively, coexisting with silicate melts containing ~1–2 wt% H ₂O. Partition coefficients measured in these experiments are consistent with the Wood-Blundy model. However, partition coefficients determined in an experiment carried out at 1.2 GPa and 1,185 °C, which produced clinopyroxene containing 19.3 wt% CaO coexisting with a high-H ₂O (6.26±0.10 wt%) silicate melt, are significantly smaller than predicted by the Wood-Blundy model. Accounting for the depolymerized structure of the H ₂O-rich melt eliminates the mismatch between experimental result and model prediction. Therefore, the increased Ca ²⁺ content of clinopyroxene at low-temperature, hydrous conditions does not enhance compatibility to the extent indicated by results from anhydrous experiments, and models used to predict mineral/melt partition coefficients during hydrous peridotite partial melting in the sub-arc mantle must take into account the effects of H ₂O on the structure of silicate melts.  相似文献   

Wine, regions and the geographic imperative: The Coonawarra example     

Glenn Banks  Scott Sharpe 《New Zealand geographer》2006,62(3):173-184

Abstract:   The growth of the global wine trade has focused attention on regional origin in the production, marketing and consumption of wine. This paper presents a case study of the regulatory processes around the development of one particular South Australian wine region: Coonawarra. The process of the delineation of the Coonawarra region illustrates the tensions between treating wine regions as biophysical entities, and the realities of the economic, political, legal and cultural forces that shape regions. The paper highlights how ambiguities in the physical and social criteria that frame regional definition legislation can lead to boundaries that form through a process of judicial accretion rather than relating directly to any of the criteria themselves.  相似文献