Future heat vulnerability in California, Part I: projecting future weather types and heat events

Excessive heat significantly impacts the health of Californians during irregular but intense heat events. Through the 21st century, a significant increase in impact is likely, as the state experiences a changing climate as well as an aging population. To assess this impact, future heat-related mortality estimates were derived for nine metropolitan areas in the state for the remainder of the century. Here in Part I, changes in oppressive weather days and consecutive-day events are projected for future years by a synoptic climatological method. First, historical surface weather types are related to circulation patterns at 500mb and 700mb, and temperature patterns at 850mb. GCM output is then utilized to classify future circulation patterns via discriminant function analysis, and multinomial logistic regression is used to derive future surface weather type at each of six stations in California. Five different climate model-scenarios are examined. Results show a significant increase in heat events over the 21st century, with oppressive weather types potentially more than doubling in frequency, and with heat events of 2?weeks or longer becoming up to ten times more common at coastal locations.     

Assessment of Offshore New Jersey Sources of Beach Replenishment Sand by Diversified Application of Geologic and Geophysical Methods

Beach replenishment serves the dual purpose of maintaining a source of tourism and recreation while protecting life and property. For New Jersey, sources for beach sand supply are increasingly found offshore. To meet present and future needs, geologic and geophysical techniques can be used to improve the identification, volume estimation, and determination of suitability, thereby making the mining and manag ing of this resource more effective. Current research has improved both data collection and interpretation of seismic surveys and vibracore analysis for projects investigating sand ridges offshore of New Jersey. The New Jersey Geological Survey in cooperation with Rutgers University is evaluating the capabilities of digital seismic data (in addition to analog data) to analyze sand ridges. The printing density of analog systems limits the dynamic range to about 24 dB. Digital acquisition systems with dynamic ranges above 100 dB can permit enhanced seismic profiles by trace static correction, deconvolution, automatic gain scaling, horizontal stacking and digital filtering. Problems common to analog data, such as wave-motion effects of surface sources, water-bottom reverberation, and bubble-pulse-width can be addressed by processing. More than 160 line miles of digital high-resolution continuous profiling seismic data have been collected at sand ridges off Avalon, Beach Haven, and Barnegat Inlet. Digital multichannel data collection has recently been employed to map sand resources within the Port of New York New Jersey expanded dredge-spoil site located 3 mi offshore of Sandy Hook, New Jersey. Multichannel data processing can reduce multiples, improve signal-to-noise calculations, enable source deconvolution, and generate sediment acoustic velocities and acoustic impedance analysis. Synthetic seismograms based on empirical relationships among grain size distribution, density, and velocity from vibracores are used to calculate proxy values for density and velocity. The seismograms are then correlated to the digital seismic profile to confirm reflected events. They are particularly useful where individual reflection events cannot be detected but a waveform generated by several thin lithologic units can be recognized. Progress in application of geologic and geophysical methods provides advan tages in detailed sediment analysis and volumetric estimation of offshore sand ridges. New techniques for current and ongoing beach replenishment projects not only expand our knowledge of the geologic processes involved in sand ridge origin and development, but also improve our assessment of these valuable resources. These reconnaissance studies provide extensive data to the engineer regarding the suitability and quantity of sand and can optimize placement and analysis of vibracore samples.     

Monitoring Colima Volcano,Mexico, using satellite data

The Colima Volcanic Complex at the western end of the Mexican Volcanic Belt is the most active andesitic volcano in Mexico. Short-wavelength infrared data from the Landsat Thematic Mapper satellite were used to determine the temperature and fractional area of radiant picture elements for two January data acquisitions in 1985 and 1986. The 1986 data showed four 28.5 m by 28.5 m pixels (picture elements) whose hot subpixel components had temperatures ranging from 511–774° C and areas of 1.8–13 m². The 1985 data had no radiating areas above background temperatures. Ground observations and measurements in November 1985 and February 1986 reported the presence of hot fumaroles at the summit with temperatures of 135–895° C. This study demonstrates the utility of satellite data for monitoring volcanic activity.     

Trends in heat-related mortality in the United States, 1975–2004

This study addresses the long-term trends in heat-related mortality across 29 US metropolitan areas from 1975 to 2004 to discern the spatial patterns and temporal trends in heat vulnerability. Mortality data have been standardized to account for population trends, and seasonal and interannual variability. On days when a city experienced an “oppressive” air mass, mean anomalous mortality was calculated, along with the likelihood that oppressive days led to a mortality response at least one standard deviation above the baseline value. Results show a general decline in heat-related mortality from the 1970s to 1990s, after which the decline seems to have abated. The likelihood of oppressive days leading to significant increases in mortality has shown less of a decline. The number of oppressive days has stayed the same or increased at most metropolitan areas. With US homes near saturation in terms of air-conditioning availability, an aging population is still significantly vulnerable to heat events.     

Volcanic history of El Chichón Volcano (Chiapas, Mexico) during the Holocene, and its impact on human activity

2 abundance and depletion in MgO, CaO, TiO₂, as well as trace and rare earth elements. This suggests segregation of olivine and orthopyroxene from the melt. Since human settlements in southeast Mexico and Central America can be traced as far back as approximately 2500 years BP, most of these events probably affected human activity. In fact, there are reports of pottery shards and other artifacts in deposits from the eruption of 1250 BP. Pottery fragments in deposits of an eruption that took place 2500 BP are also reported in this paper. Thus, the impact of the volcano on human activities has been frequent, with most of the repose intervals lasting between 100 to 600 years. The impact of the eruptions was probably of greater than local extent, because airfall tephra could reach distant sites and possibly even affect weather. The eruptive history of El Chichón also offers clues in the investigation of the Maya civilization. Several researchers have considered the volcano as an important factor in the answer to some intriguing questions such as the extensive use of volcanic ash in Late Classic Maya ceramics or, of greater importance, the causes of the collapse of the Classic Maya civilization. Received : 4 May 1998 / Accepted: 1 November 1999     

Volcanic hazards at Fossa of Vulcano: Data from the last 6,000 years

Stratigraphic reconstruction of the complete sequence of deposits that formed the Fossa cone of Vulcano has distinguished four principal eruptive cycles: Punte Nere, Palizzi, Commenda, and Pietre Cotte. At least three additional eruptive cycles, one of which ends with the Campo Sportivo lava, occur between deposits of the Punte Nere and Palizzi cycles. However, exposure is inadequate for their characterization. The assignment of the modern deposits that follow the Pietre Cotte lava is uncertain.Deposits of each cycle follow a similar stochastic pattern that is controlled by a decrease in the effect of water/melt interaction. The normal sequence of pyroclastic products for each cycle starts with wet-surge beds, followed by dry-surge horizons, fall deposits, and finally lava flows. Absolute age determinations have been made on each cycle-ending lava flow.Wet-surge deposits normally occur near the crater rim, whereas dry-surge deposits are more widespread, reaching the surrounding caldera wall in many places. Thick fall deposits are confined to a zone extending about 800 m from the crater rim. Lava flows normally reach the base of the cone. The greatest hazard at Fossa is related to surge eruptions. The thickness of dry-surge deposits on the flanks of the cone increases away from the crater, but they pinch out toward the source near the crater rim. SEM analysis of the surface textures of juvenile glass clasts from dry-surge deposits confirms that the dominant control on the eruptive mechanism is water/melt interaction. Only slight modifications are induced on grain surfaces during transport. Particles from the Palizzi dry-surge beds lack surface textures characteristic of fall pyroclasts which suggests that ballistic fragments were not incorporated into the dense portion of the turbulent surge cloud. A quantitative analysis of the dispersal of products from the Palizzi cycle allowed creation of a computer-generated map for this eruption.Paper presented at the IUGG Inter-disciplinary Symposium on Volcanic Hazard, Hamburg, August 1983.     

The petrogenesis of topaz rhyolites from the western United States

High-silica topaz-bearing rhyolites of Cenozoic age are widely distributed across the western USA and Mexico. They are characteristically enriched in fluorine (>0.2 wt.%) and incompatible lithophile elements (e.g. Li, Rb, Cs, U, Th, Be). In addition to topaz, the rhyolites contain garnet, bixbyite, pseudobrookite, hematite and fluorite in cavities or in their devitrified groundmasses. Magmatic phases include sanidine, quartz, oligoclase and Fe-rich biotite. Allanite, fluorite, zircon, apatite and magnetite occur in most; pyroxene, hornblende, ilmenite and titanite occur in some. The rhyolites crystallized over a wide temperature interval (850° to 600° C) at \(f_{0_2 } \) that ranges from QFM to NNO. The REE patterns of most topaz rhyolites are almost flat (La/Yb_N=1 to 3) and have deep Eu anomalies (Eu/Eu^*=0.01 to 0.02). Both parameters decrease with differentiation. Titanite-bearing rhyolites have prominent middle REE depletions. Topaz rhyolites appear to have evolved from partial melts of a residual granulitic source in the Precambrian lower crust. According to the proposed model, the passage of hot mafic magmas through the crust produced partial melts as a result of the decomposition of F-rich biotite or amphibole. An extensional tectonic setting allowed these small batches of magma to rise without substantial mixing with contemporaneous mafic magmas. Some of the compositional differences between topaz rhyolites and peralkaline rhyolites may be attributed to the accumulation of fluorine and fluorphile elements (Al, Be, Li, Rb, U, Th, HREE) in melts which give rise to topaz rhyolites and chlorine and chlorophile elements (Ti, Fe, Mn, Zn, Zr, Nb and LREE) in melts which yield peralkaline rhyolites. Hence the F/Cl ratio of the melt or its source may determine the alumina saturation of the magma series. Topaz rhyolites are distinguishable from calc-alkaline rhyolites by lower Sr, Ba, Eu and higher F, Rb, U and Th. The usually low La/Yb ratios of topaz rhyolites distinguish them from both peralkaline and calc-alkaline rhyolite suites.     

A tertiary silicic cauldron complex at the northern margin of the basin and range province,central Arizona,U.S.A.

The Superior volcanic field occupies approximately 8,000 square kilometers of central Arizona in the zone between the southern Basin and Range Province and the Colorado Plateaus Province. The primary structural elements of an eruptive center in the western part of this field are: 1) volcanic plateau, 2) ring fracture zone, and 3) resurgent caldera core. A northwest trending graben controls the location of three small subsided blocks, the Willow Springs cauldron (2 km diameter), the Black Mesa cauldron (4 km diameter), and the Florence Junction cauldron (8 km diameter), which were centers for rhyolite ash and lava eruption. These late features are superimposed on a much larger volcano-tectonic structure, the Superstition resurgent cauldron which subsided at an earlier stage following the extrusion of quartz latite welded tuff. The history of the volcanic center is as follows: An early ring of dacite domes of up to 900 meters in relief formed a semi-circular are 7 km in diameter on the western margin of the caldera. The last phases of dome building were contemporaneous with the extrusion of a vast quartz latite welded tuff (22.6 m.y.). The plateau formed by the welded tuff collapsed to a maximum depth of 800 meters along a northwest trending graben which is the locus of three small cauldrons. These late cauldrons were the source of rhyolitic magma which produced non-welded ash flows, lava (21 m.y.), and a thick sequence of epiclastic breccias. The rhyolitic volcanism was followed by intrusion of domes and extrusion of glassy lavas (20 m.y.) of quartz latite composition in a 270° are 16 km in diameter concentric to the arc of older dacite domes. Following deposition of the epiclastic breccia and intrusion of the ring fracture dikes was the extrusion of mafic lava (18 m.y.) into low places in the graben. The mafic lava composition ranges from basalt to basanite.