Turbidity trends at tucson, Arizona

Variations in atmospheric turbidity at Tucson, Arizona, since 1956 are similar to those at Mauna Loa in Hawaii, especially before January 1970. The turbidity at both locations increased markedly in 1963 after the Bali eruption. Since January 1970, the turbidity has returned to its pre-1963 level at Mauna Loa, but has remained relatively high at Tucson.     

Volcanically related secular trends in atmospheric transmission at mauna loa observatory, hawaii

Twenty years of atmospheric transmission data from Mauna Loa Observatory show secular decreases at irregular intervals. In addition, a regular annual variation is present during unperturbed as well as perturbed periods. These variations in transmission can be measured to a few tenths of a percent from the data record. Transient decreases in transmission are strongly correlated with explosive volcanic eruptions that inject effluent into the stratosphere. Recovery from these ejections takes as much as 8 years and the recovery curve is linear. Observations in 1977 at Mauna Loa show that, for the first time since the Mount Agung eruption in 1963, the atmospheric transmission of direct-incidence solar irradiation at Mauna Loa returned to values measured in 1958 to 1962.     

Asian dust: seasonal transport to the hawaiian islands

Analyses of atmospheric particles collected at Mauna Loa Observatory in Hawaii from February 1979 through September 1982 reveal strong influxes of Asian dust in the spring of each year. Concentrations of a typical crustal element, aluminum, are more than an order of magnitude greater between February and June than during the remainder of the year (71 +/- 51 versus 6.7 +/- 2.3 nanograms per cubic meter). The mass of crustal material transported during the relatively short dust episodes accounts for an average of 80 percent of the total yearly mass of atmospheric particles at 3400 meters on Mauna Loa.     

Radiative properties of the background aerosol: absorption component of extinction

The light-scattering and light-absorption coefficients of the global background aerosol define its single-scatter albedo. Continuous, simultaneous measurements of these optical coefficients were made on a daily basis for the remote marine mid-troposphere; such measurements are essential for assessment of the effects of aerosol on atmospheric radiative transfer. Measurements of light-absorption coefficients made at the Mauna Loa Observatory in Hawaii were higher than expected, and the single-scatter albedo was lower than the value often used in radiative transfer models. Soot appears to be the most likely primary absorber, and hemispheric dispersal of this combustion-derived material is suggested.     

Holocene eruptions of mauna kea volcano, hawaii

Postglacial lava flows, interstratified with thick locally derived sheets of tephra, cover some 27.5 square kilometers on the south slope of Mauna Kea. Most of the volcanics were erupted about 4500 years ago and overlie a regionally extensive paleosol which developed largely during the last glaciation.     

Stress control of deep rift intrusion at Mauna Loa volcano, Hawaii

Mauna Loa volcano, Hawaii, deforms by a combination of shallow dike intrusions in the rift zones and earthquakes along the base of the volcano, but it is not known how the spreading is accommodated in the lower part of the volcanic edifice. We present evidence from interferometric synthetic aperture radar data for secular inflation of a dike-like magma body at intermediate depth in the southwest rift zone during 2002 to 2005. Magma accumulation occurred in a section of the rift zone that was unclamped by previous dikes and earthquakes, suggesting that stress transfer plays an important role in controlling subsurface magma accumulation.     

Iridium enrichment in airborne particles from kilauea volcano: january 1983

Airborne particulate matter from the January 1983 eruption of Kilauea volcano was inadvertently collected on air filters at Mauna Loa Observatory at a sampling station used to observe particles in global circulation. Analyses of affected samples revealed unusually large concentrations of selenium, arsenic, indium, gold, and sulfur, as expected for volcanic emissions. Strikingly large concentrations of iridium were also observed, the ratio of iridium to aluminum being 17,000 times its value in Hawaiian basalt. Since iridium enrichments have not previously been observed in volcanic emissions, the results for Kilauea suggest that it is part of an unusual volcanic system which may be fed by magma from the mantle. The iridium enrichment appears to be linked with the high fluorine content of the volcanic gases, which suggests that the iridium is released as a volatile IrF(6).     

Sulfur and chlorine in late Cretaceous Deccan magmas and eruptive gas release

Large-volume pāhoehoe lava flows erupted 67 to 65 million years ago, forming the Deccan Traps, India. The impact of these flood basalt eruptions on the global atmosphere and the coeval end-Cretaceous mass extinction has been uncertain. To assess the potential gas release from this volcanism, we measured sulfur and chlorine concentrations in rare glass inclusions inside crystals and on glassy selvages preserved within lavas. Concentrations range from approximately 1400 parts per million of S and 900 parts per million of Cl in inclusions down to a few hundred parts per million in the lava. These data indicate that eruptions of Deccan lavas could have released at most 0.103 weight % of S, yielding up to 5.4 teragrams of SO2 per cubic kilometer of lava. A more conservative estimate is 0.07 weight % of S and 0.04 weight % of Cl, yielding 3.5 teragrams of SO2 and 1 teragram of HCl for every cubic kilometer of lava erupted. The flows were very large in volume, and these results imply that huge amounts of S and Cl gases were released. The environmental impact from even individual eruptions during past flood basalt activity was probably severe.     

Rare earths: atmospheric signatures for oil-fired power plants and refineries

The concentration pattern of rare earth elements on fine airborne particles (less than 2.5 micrometers in diameter) is distorted from the crustal abundance pattern in areas influenced by emissions from oil-fired plants and refineries. For example, the ratio of lanthanum to samarium is often greater than 20 compared to a crustal ratio less than 6. The unusual pattern apparently results from the distribution of rare earths in zeolite catalysts used in refining oil. Oil industry emissions perturb the rare earth pattern even at remote locations such as the Mauna Loa Observatory in Hawaii. Rare earth ratios are probably better for long-range tracing of oil emissions than vanadium and nickel concentrations because the ratios of rare earths on fine particles are probably not influenced by deposition and other fractionating processes. Emissions from oil-fired plants can be differentiated from those of refineries on an urban scale by the much smaller amounts of vanadium in the latter.     

The columbia river basalts

Between 17 million and 6 million years ago, 200,000 square kilometers of the American Northwest were flooded by basaltic lava that erupted through fissures in the crust up to 150 kilometers long. Larger individual eruptions covered over a third of the Columbia Plateau in a few days. The lavas represent partial melts of the earth's mantle that were only slightly modified by near-surface, upper crustal processes. The abundant chemical and mineralogical data now available offer an opportunity to study mantle composition and the processes involved in the evolution of the earth's crust.     

Deep-ocean basalts: inert gas content and uncertainties in age dating

The radiogenic argon and helium contents of three basalts erupted into the deep ocean from an active volcano (Kilauea) have been measured. Ages calculated from these measurements increase with sample depth up to 22 million years for lavas deduced to be recent. Caution is urged in applying dates from deep-ocean basalts in studies on ocean-floor spreading.     

Andesitic Volcanism and Seismicity around the Pacific

Circum-Pacific andesites, with associated basalts and dacites, are erupted from linear island arcs and marginal continental ranges whose ocean-side borders coincide approximately with the continent-side boundaries of belts of shallow seismicity that parallel adjacent trenches. The lines of active volcanoes stand above elongate subcrustal regions delineated by the intersection of inclined Benioff seismic zones and the subhorizontal Gutenberg low-velocity zone. Close correlation between content of potash in erupted lavas and vertical depth to the Benioff zone suggests that andesitic volcanism has its origins in the mantle where magmas are generated by events associated with earthquakes of intermediate focal depth.     

Earthquake potential along the northern hayward fault, california

The Hayward fault slips in large earthquakes and by aseismic creep observed along its surface trace. Dislocation models of the surface deformation adjacent to the Hayward fault measured with the global positioning system and interferometric synthetic aperture radar favor creep at approximately 7 millimeters per year to the bottom of the seismogenic zone along a approximately 20-kilometer-long northern fault segment. Microearthquakes with the same waveform repeatedly occur at 4- to 10-kilometer depths and indicate deep creep at 5 to 7 millimeters per year. The difference between current creep rates and the long-term slip rate of approximately 10 millimeters per year can be reconciled in a mechanical model of a freely slipping northern Hayward fault adjacent to the locked 1868 earthquake rupture, which broke the southern 40 to 50 kilometers of the fault. The potential for a major independent earthquake of the northern Hayward fault might be less than previously thought.     

Pb isotopic variability in melt inclusions from oceanic island basalts, polynesia

Previous studies have suggested that melting processes are responsible for the trace element variability observed in olivine-hosted basaltic melt inclusions. Melt inclusions from three individual lava samples (two from Mangaia, Cook Islands, and one from Tahaa, Society Islands) have heterogeneous Pb isotopic compositions, even though the erupted lavas are isotopically homogeneous. The range of Pb isotopic compositions from individual melt inclusions spans 50 percent of the worldwide range observed for ocean island basalts. The melt inclusion data can be explained by two-component mixing for each island. Our data imply that magmas with different isotopic compositions existed in the volcanic plumbing system before or during melt aggregation.     

Geochemical evidence for excess iron in the mantle beneath Hawaii

Chemical interaction of Earth's mantle with the liquid outer core should influence the mantle's iron content. Osmium isotope ratios in Hawaiian lavas indicate a mass flux of 相似文献   

Interferometric coupling of the Keck telescopes with single-mode fibers

Here we report successful interferometric coupling of two large telescopes with single-mode fibers. Interference fringes were obtained in the 2- to 2.3-micrometer wavelength range on the star 107 Herculis by using the two Keck 10-meter telescopes, each feeding their common interferometric focus with 300 meters of single-mode fibers. This experiment demonstrates the potential of fibers for future kilometric arrays of telescopes and is the first step toward the 'OHANA (Optical Hawaiian Array for Nanoradian Astronomy) interferometer at the Mauna Kea observatory in Hawaii. It opens the way to sensitive optical imagers with resolutions below 1 milli-arc second. Our experimental setup can be directly extended to large telescopes separated by many hundreds of meters.     

No evidence of a circumsolar dust ring from infrared observations of the 1991 solar eclipse

During the past 25 years there have been many attempts to detect a possible dust ring around the sun, with contradictory results. Before the 1991 eclipse, infrared eclipse experiments used single-element detectors to scan the corona along the ecliptic for excess surface brightness peaks. The availability of relatively large-format infrared array detectors now provides a considerable observational advantage: two-dimensional mapping of the brightness and polarization of the corona with high photometric precision. The 1991 eclipse path included the high-altitude Mauna Kea Observatory, a further advantage to measure the corona out to large angular distances from the sun. Results are reported from an experiment conducted on Mauna Kea with a HgCdTe-array detector sensitive to wavelengths between 1 and 2.5 micrometers, using broad-band J, H, and K filters. Although the sky conditions were not ideal, the H- and K-band surface brightnesses clearly show the inhomogeneous structure in the K-corona and the elliptical flattening of the F-corona, but no evidence of a circumsolar, local dust component out to 15 solar radii.     

Response of regional seismicity to the static stress change produced by the loma prieta earthquake

The 1989 Loma Prieta, California, earthquake perturbed the static stress field over a large area of central California. The pattern of stress changes on major faults in the region predicted by models of the earthquake's dislocation agrees closely with changes in the regional seismicity rate after the earthquake. The agreement is best for models with low values of the coefficient of friction (0.1 相似文献   

Halite particles injected into the stratosphere by the 1982 el chichon eruption

Halite particles about 2 micrometers in size were collected by a quartz crystal microbalance cascade impactor from the El Chichón eruption cloud in the lower stratosphere during April and May 1982. These particles are probably derived from the erupted chloride-rich, alkalic magma. Enrichments of hydrogen chloride and increases in optical depolarization in the eruption cloud observed by lidar measurements may reflect the influence of the halite particles. There is evidence that the halite particles reacted with sulfuric acid after about 1 month, releasing gaseous hydrogen chloride, which can influence the catalytic destruction of ozone in the stratosphere.     

Controversy of the year. Biomedical ethics on the front burner

CONTROVERSY OF THE YEAR: Biomedical Ethics on the Front Burner It was a hot year for debates over research ethics. Controversy erupted in late 1999 after the death of 18-year-old Jesse Gelsinger in a gene-therapy clinical trial at the University of Pennsylvania. Because Penn and one of its clinicians had a financial stake in a gene-therapy company, questions about potential conflicts of interest arose at once.