Eclipse reappearances of Io: Time-resolved spectroscopy (1.9-4.2 μm)

We obtained time-resolved, near-infrared spectra of Io during the 60-90 min following its reappearance from eclipse by Jupiter on five occasions in 2004. The purpose was to search for spectral changes, particularly in the well-known SO₂ frost absorption bands, that would indicate surface-atmosphere exchange of gaseous SO₂ induced by temperature changes during eclipse. These observations were a follow-on to eclipse spectroscopy observations in which Bellucci et al. [Bellucci et al., 2004. Icarus 172, 141-148] reported significant changes in the strengths of two strong SO₂ bands in data acquired with the VIMS instrument aboard the Cassini spacecraft. One of the bands (4.07 μm [ν₁ + ν₃]) observed by Bellucci et al. is visible from ground-based observatories and is included in our data. We detected no changes in Io’s spectrum at any of the five observed events during the approximately 60-90 min during which spectra were obtained following Io’s emergence from Jupiter’s shadow. The areas of the three strongest SO₂ bands in the region 3.5-4.15 μm were measured for each spectrum; the variation of the band areas with time does not exceed that which can be explained by the Io’s few degrees of axial rotation during the intervals of observation, and in no case does the change in band strength approach that seen in the Cassini VIMS data. Our data are of sufficient quality and resolution to show the weak 2.198 μm (4549.6 cm⁻¹) 4ν₁ band of SO₂ frost on Io for what we believe is the first time. At one of the events (June 22, 2004), we began the acquisition of spectra ∼6 min before Io reappeared from Jupiter’s shadow, during which time it was detected through its own thermal emission. No SO₂ bands were superimposed on the purely thermal spectrum on this occasion, suggesting that the upper limit to condensed SO₂ in the vertical column above Io’s surface was ∼4 × 10⁻⁵ g cm⁻².     

Temperature oscillations may shorten male lifespan via natural selection in utero

Much literature argues that natural selection has conserved mechanisms that spontaneously abort fetuses, particularly males, least likely to survive in prevailing environmental conditions including cold ambient temperature. These reports imply the hypothesis that males in gestation during relatively warm periods who confront relatively cold climates in early life live, on average, shorter lives than other males. We estimate the effect of warm-to-cold temperature shifts on the observed lifespan at age one of males born in Sweden from 1850 through 1915. We test this hypothesis using annual cohort lifespan at age 1?year for Swedish males from 1850 to 1915. For our independent variable, we score a series “1” for birth cohorts that experienced relatively warm temperatures in utero but relatively cold temperatures from age 1 through 4?years, and “0” for other cohorts. We use time-series methods, which adjust the data to remove autocorrelation, to estimate the association between these variables. Consistent with theory, males in gestation during relatively warm times who encounter relatively cold temperatures in early life have a shorter lifespan than other males. The association survives adjustment for the longevity of females as well as the main effect of temperatures during gestation and early life. Our findings imply that the increased frequency and amplitude of temperature shifts expected from climate change could influence which humans survive gestation and how long they live.     

Understanding Causes and Impacts of the Dinoflagellate, Cochlodinium polykrikoides, Blooms in the Chesapeake Bay

During August and September 2007, the lower Chesapeake Bay and its tributaries experienced a massive bloom of Cochlodinium polykrikoides Margalef (>10⁴ cells per milliliter) that persisted for over a month, was extremely patchy, and at times penetrated into the Atlantic Ocean. The onset of the bloom coincided with a period of intense rainfall and stormwater runoff after a protracted summer drought period. Genetic evidence showed this species to be distinct from many Asian strains but similar to other North American strains. Populations dominated by C. polykrikoides took up a variety of nitrogenous compounds to support their growth and were able to mobilize additional sources of organic nutrients through peptide hydrolysis. Bioassays determined that C. polykrikoides exerted a lethal affect on juvenile fish and shellfish, causing 100% mortality of juvenile fish (Cyprinodon variegates) in less than 24 h and 20% mortality in juvenile American oysters (~21 mm; Crassostrea virginica) within 72 h.     

Application of spatial prediction techniques to defining three-dimensional landslide shear surface geometry

This study explores the application of interpolating and non-interpolating spatial prediction algorithms to interpreting shear surface geometries. A number of spatial prediction techniques have been tested, and the most appropriate algorithms for the Downie Slide dataset have been selected based on the root mean squared error (RMSE) determined from cross-validation. Visual assessment of reasonable spatial patterns has allowed for final selection of algorithms that produce geologically realistic results. Through this process, the performance of a number of interpolation algorithms has been tested in terms of accuracy and the development of reasonable spatial patterns. The goal of this study has been: (a) to develop a methodology for interpolating three-dimensional shear surface geometries and (b) to assess which interpolation methods are most appropriate for the interpretation of the Downie Slide basal slip surface geometry, based quantitatively on RMSE and qualitatively on the geological “trueness” of the geometric output.     

Characterising the hydrothermal alteration of the Broadlands–Ohaaki geothermal system, New Zealand, using short-wave infrared spectroscopy

Hydrothermal clay minerals present in the Broadlands–Ohaaki geothermal field were characterised by field portable short-wave infrared spectroscopy. Three major alteration zones, an upper smectite, a middle illite and a lower illite–chlorite, are spectrally separable. The zoning pattern is generally consistent with the thermal structure of the geothermal field, although occasionally zone boundaries cut present-day isotherms. The data indicate that temperature is the major control on clay zoning and permeability plays a subordinate role.Both beidellite and montmorillonite are common in the upper, low-temperature smectite zone. Kaolinite, mainly of low crystallinity, marks the margin of the field where cool acidic ground waters inflow. In the middle alteration zone, illite, dominantly K-rich, shows a narrow compositional variability. Some highly permeable zones are characterised by illite with low octahedral Al contents. Ammonium-bearing illite and buddingtonite are present locally in permeable horizons within the illite zone, where temperatures are above 200°C. Chlorite is most abundant in the lower alteration zone (temperature >250°C), although it also occurs unevenly in the upper and middle alteration zones. Chlorite varies from Mg- to Fe-rich varieties (but mostly with Mg# values <0.5), but no compositional trends with respect to depth are spectrally detectable.     

Infrared spectral reflectance characterization of the hydrothermal alteration at the Tuwu Cu–Au deposit, Xinjiang, China

Short-wave infrared (SWIR) reflectance spectroscopy was used to characterize hydrothermal minerals and map alteration zones in the Tuwu Cu–Au deposit, Xinjiang, China. The Palaeozoic hydrothermal system at Tuwu is structurally controlled, developed in andesitic volcanic rocks and minor porphyries. Hydrothermal alteration is characterized by horizontally zoned development of quartz, sericite, chlorite, epidote, montmorillonite and kaolin about individual porphyry dykes and breccia zones, as is shown by changes outward from a core of quartz veining and silicification, through an inner zone of sericite + chlorite to a marginal zone of chlorite + epidote. The alteration system comprises several such zoning patterns. Silicification and sericitization are spatially associated with Cu–Au mineralization. Zoning is also shown by compositional variations such that Fe-rich chlorite and Al-rich sericite occur preferentially toward the core and the most intensely altered parts, whereas Mg-rich chlorite and relatively Al-poor sericite are present on the margin and the relatively weakly altered parts of the hydrothermal alteration system. The compositions of chlorite and sericite, therefore, can be potentially used as vectors to Cu–Au mineralization. Montmorillonite and kaolinite, of probable weathering origin, are located near the surface, forming an argillic blanket overlying Cu–Au mineralization. Sporadic montmorillonite is also present at depth in the hydrothermal alteration system, formed by descending groundwater. Presence of a well-developed kaolinite-bearing zone on the surface is an indication of possible underlying Cu–Au mineralization in this region. Epidote occurs widely in regional volcanic rocks, as well as in variably altered rocks on the margin of the hydrothermal mineralization system at Tuwu. The widespread occurrence of epidote in volcanic country rocks probably reflects a regional hydrothermal alteration event prior to the localized, porphyry intrusion-related hydrothermal process that led to the Cu–Au mineralization at Tuwu.     

Participatory action research in a poststructuralist vein

This paper introduces a participatory action research process that has been shaped by poststructuralist thought. We report on the stages and outcomes of a project conducted in the Latrobe Valley, Victoria, Australia, a resource region that has experienced downsizing and privatising of its major employer, the state-owned power industry. Through a participatory action research process involving community members, local Council and academic researchers the singular economic identity of the region was challenged and a more enabling representation developed. Drawing on a discourse of the diverse economy and the asset-based approach to community development the project shed light on the wide range of economic activities residents were already engaged in and the multitude of abilities and ideas they possessed. This exercise produced a new representation of the economy of the Latrobe Valley that helped to shift the vision of what was possible in the region. In the final stage of the project this alternative vision was acted on as groups turned shared ideas into projects and those who were most used to being defined as economically dependent and victims of economic circumstances increasingly came to identify as active and contributing economic subjects in the diverse economy. The paper considers the role of subjectivity, representation and micropolitics in participatory action research and concludes with a reflection on the project’s strengths and weaknesses.     

Ubinas: the evolution of the historically most active volcano in southern Peru

Ubinas volcano has had 23 degassing and ashfall episodes since A.D. 1550, making it the historically most active volcano in southern Peru. Based on fieldwork, on interpretation of aerial photographs and satellite images, and on radiometric ages, the eruptive history of Ubinas is divided into two major periods. Ubinas I (Middle Pleistocene >376 ka) is characterized by lava flow activity that formed the lower part of the edifice. This edifice collapsed and resulted in a debris-avalanche deposit distributed as far as 12 km downstream the Rio Ubinas. Non-welded ignimbrites were erupted subsequently and ponded to a thickness of 150 m as far as 7 km south of the summit. These eruptions probably left a small collapse caldera on the summit of Ubinas I. A 100-m-thick sequence of ash-and-pumice flow deposits followed, filling paleo-valleys 6 km from the summit. Ubinas II, 376 ky to present comprises several stages. The summit cone was built by andesite and dacite flows between 376 and 142 ky. A series of domes grew on the southern flank and the largest one was dated at 250 ky; block-and-ash flow deposits from these domes filled the upper Rio Ubinas valley 10 km to the south. The summit caldera was formed between 25 and 9.7 ky. Ash-flow deposits and two Plinian deposits reflect explosive eruptions of more differentiated magmas. A debris-avalanche deposit (about 1.2 km³) formed hummocks at the base of the 1,000-m-high, fractured and unstable south flank before 3.6 ka. Countless explosive events took place inside the summit caldera during the last 9.7 ky. The last Plinian eruption, dated A.D.1000–1160, produced an andesitic pumice-fall deposit, which achieved a thickness of 25 cm 40 km SE of the summit. Minor eruptions since then show phreatomagmatic characteristics and a wide range in composition (mafic to rhyolitic): the events reported since A.D. 1550 include many degassing episodes, four moderate (VEI 2–3) eruptions, and one VEI 3 eruption in A.D. 1667. Ubinas erupted high-K, calc-alkaline magmas (SiO₂=56 to 71%). Magmatic processes include fractional crystallization and mixing of deeply derived mafic andesites in a shallow magma chamber. Parent magmas have been relatively homogeneous through time but reflect variable conditions of deep-crustal assimilation, as shown in the large variations in Sr/Y and LREE/HREE. Depleted HREE and Y values in some lavas, mostly late mafic rocks, suggest contamination of magmas near the base of the >60-km-thick continental crust. The most recently erupted products (mostly scoria) show a wide range in composition and a trend towards more mafic magmas.Recent eruptions indicate that Ubinas poses a severe threat to at least 5,000 people living in the valley of the Rio Ubinas, and within a 15-km radius of the summit. The threat includes thick tephra falls, phreatomagmatic ejecta, failure of the unstable south flank with subsequent debris avalanches, rain-triggered lahars, and pyroclastic flows. Should Plinian eruptions of the size of the Holocene events recur at Ubinas, tephra fall would affect about one million people living in the Arequipa area 60 km west of the summit.Editorial responsibility: D Dingwell