Gas emissions from failed and actual eruptions from Cook Inlet Volcanoes,Alaska, 1989–2006

Cook Inlet volcanoes that experienced an eruption between 1989 and 2006 had mean gas emission rates that were roughly an order of magnitude higher than at volcanoes where unrest stalled. For the six events studied, mean emission rates for eruptions were ∼13,000 t/d CO₂ and 5200 t/d SO₂, but only ∼1200 t/d CO₂ and 500 t/d SO₂ for non-eruptive events (‘failed eruptions’). Statistical analysis suggests degassing thresholds for eruption on the order of 1500 and 1000 t/d for CO₂ and SO₂, respectively. Emission rates greater than 4000 and 2000 t/d for CO₂ and SO₂, respectively, almost exclusively resulted during eruptive events (the only exception being two measurements at Fourpeaked). While this analysis could suggest that unerupted magmas have lower pre-eruptive volatile contents, we favor the explanations that either the amount of magma feeding actual eruptions is larger than that driving failed eruptions, or that magmas from failed eruptions experience less decompression such that the majority of H₂O remains dissolved and thus insufficient permeability is produced to release the trapped volatile phase (or both). In the majority of unrest and eruption sequences, increases in CO₂ emission relative to SO₂ emission were observed early in the sequence. With time, all events converged to a common molar value of C/S between 0.5 and 2. These geochemical trends argue for roughly similar decompression histories until shallow levels are reached beneath the edifice (i.e., from 20–35 to ∼4–6 km) and perhaps roughly similar initial volatile contents in all cases. Early elevated CO₂ levels that we find at these high-latitude, andesitic arc volcanoes have also been observed at mid-latitude, relatively snow-free, basaltic volcanoes such as Stromboli and Etna. Typically such patterns are attributed to injection and decompression of deep (CO₂-rich) magma into a shallower chamber and open system degassing prior to eruption. Here we argue that the C/S trends probably represent tapping of vapor-saturated regions with high C/S, and then gradual degassing of remaining dissolved volatiles as the magma progresses toward the surface. At these volcanoes, however, C/S is often accentuated due to early preferential scrubbing of sulfur gases. The range of equilibrium degassing is consistent with the bulk degassing of a magma with initial CO₂ and S of 0.6 and 0.2 wt.%, respectively, similar to what has been suggested for primitive Redoubt magmas.     

Sulfur-rich monazite with high common Pb in ore-bearing schists from the Schellgaden mining district (Tauern Window, Eastern Alps)

The compositional variation of accessory monazite in ore bearing micaschists from the Schellgaden mining district, Tauern Window, Eastern Alps, was studied by means of the electron microprobe. In ore-rich domains monazite yields unusually high sulfur contents (up to 2.5?wt.% SO₃), which enter the monazite structure together with Ca and Sr as ??anhydrite-celestine?? component replacing P and REEs. The exchange reaction is S⁶⁺+ (Ca, Sr)²⁺ = REE³⁺+ P⁵⁺. Sulfur-rich monazite is intergrown with anglesite, pyromorphite or galena and shows oscillatory zoning indicating growth from S-bearing fluids. This type of S-enriched monazite yields very high common lead contents (up to 0.5?wt.% PbO) and unrealistic high apparent Th-U-total Pb single dates (> 1?Ga). However, S-enriched monazite grains provide a flat trendline in the Th* vs. Pb isochron diagram similar to the trendline defined through low-S, and low-Pb monazite crystals (0.1?C1?wt.% SO₃, < 0.05?wt.% PbO), which were observed in ore-poor parts of micaschists. Results from this study imply an Alpine rather than a pre-Alpine formation age for monazite and a strong S-rich fluid activity during the Alpine orogeny. Apart from this geological aspect, the current study also shows that the detection of sulfur in monazite may serve as a warning for a possible presence of common Pb.     

Influence of habitat structure on fish assemblage of an artificial reef in southern Brazil

Habitat complexity strongly influences reef fish community composition. An understanding of the underlying reasons for this relationship is important for evaluating the suitability of artificial reef (AR) habitats as a marine resource management tool. We studied the influence of AR habitat structure on fish assemblage composition off the southern coast of Brazil. We found that reef blocks with greater area and number of holes possessed the greatest fish species richness and abundance. Reef blocks with greater complexity had higher abundance of almost 30% of fish species present. Natural reef (NR) and AR were different in their fish species composition, trophic structure and categories of water column occupancy by fish (spatial categories). Although NR was more diverse and harboured more trophic levels, AR presented the higher abundances and the presence of distinct fish species that underlined their importance at a regional scale. The greater availability of sheltering habitat where hard substrate is scarce, together with their frequent use by economically important species, make AR a useful tool for coastal management when certain ecological conditions are met.     

Winter storm- and summer thunderstorm-related loss events with regard to climate change in Germany

The development of winter storm- and summer thunderstorm-related loss events within the next decades in Germany was investigated with regard to change in frequency and intensity caused by climate changes. As a first step, observed meteorological data were connected with insurance data on a statistical basis. A regional climate model was then used to estimate future climate development. Using the statistical relations between meteorological and insurance data, the development of climate-driven damages was calculated. Results show that an increase of loss events can be expected within the next decades. These results show loss ratios shifting from higher return periods to smaller ones. In progressive decades, all these loss events become regionally more differentiated.     

Stable isotopes in surface snow along a traverse route from Zhongshan station to Dome A, East Antarctica

Samples of surface snow were collected for stable isotope analysis along the traverse route from Zhongshan to Dome A (East Antarctica) from Dec 28th, 2007 to Feb. 8th, 2008. The local relationship between δD and surface temperature is established to be 6.4 ± 0.2 ‰ per °C, very similar to the average for East Antarctic. The deuterium excess shows a pattern of high values over Antarctica, particularly at Dome A. We compare our data with an atmospheric general circulation model which includes stable water isotopes (ECHAM5-wiso). The model simulation captures the right levels of δD, but overestimates δ¹⁸O. This study provides support for the ongoing deep ice core project at Dome A.     

An EUV imaging spectrograph for high-resolution observations of the solar corona

An extreme ultraviolet (EUV) imaging spectrograph for the wavelength range from 235 to 450 Å has been developed and used for high resolution observations of the Sun. The instrument incorporates a glancing incidence Wolter Type II Telescope and a near-normal incidence toroidal grating spectrograph to achieve near-stigmatic performance over this spectral range. The design of the spectrograph entrance aperture enables both stigmatic spectra with spectral resolution adequate to observe emission line profiles and spectroheliograms of restricted portions of the Sun to be obtained concurrently. In this paper we describe the design and performance of the instrument and provide an overview of results obtained during a sounding rocket flight on May 5, 1989.     

UV and optical spectral properties in early-type galaxies

We investigate UV and optical spectra of a sample of nearby early-type galaxies with evidence of nuclear line emission. The spectral signatures of various contributors to the UV, such as the interstellar medium and various stellar populations are analyzed and compared with the optical spectral properties. We discuss the impact of these effects on the observational properties of galaxy evolution. This revised version was published online in August 2006 with corrections to the Cover Date.