Geological and geochemical studies of the sintra alkaline igneous complex,portugal

The Sintra igneous complex, Portugal was an important centre of activity in late Cretaceous times. The great proportion of thealkaline rocks are felsic and include five large quartz syenite intrusions and trachyandesite, trachyte and alkali rhyolite lavas and dykes, most of which are oversaturated. Mafic rocks are sparse, but vary widely from alkaline and highly undersaturated types containing high K₂O, TiO₂ and Ba, similar to the contemporaneous Lisbon lavas, to hypersthene normative trachybasalts and one hypersthene normative basalt. The various magma types are intimately associated and a well-developed netveined complex of alkali gabbro, monzonite and syenite is recognised at Cabo da Roca. A study of the dyke distributions, intersections and orientations suggest a close propinquity of both oversaturated and undersaturated and of both felsic and matic magmas. The basic magmas of Sintra and Lisbon show a continuous range in undersaturation (0 to 16% normative nepheline) and rare hypersthene normative basalts. Derivation of the hypersthene normative and mildly undersaturated basalts from the more undersaturated melts by low pressure fractionation or contamination by siliceous crust is shown to be unlikely. High pressure eclogite fractionation of a hypersthene normative basalt or variations in the percentage partial melting of a mantle under conditions where titanphlogopite is a low melting fraction are both processes compatible with the variations in undersaturation and proportions of TiO₂, K₂O and Ba. The quartz syenites and over satured felsic lavas of Sintra are thought to be derived from hypersthene nor mative parents.     

Deformation of Mount Etna, 1971–1974

Electro-optical distance measurements made on the summit of Mt. Etna from 1971 to 1974 show evidence of large surface deformation of the volcano. This deformation cannot be satisfactorily analysed in terms of the models of subsurface magma reservoirs of various geometries that have been previously used, as they have, for instance, on Kilauea in Hawaii. A model that gives a better fit between the observed and computed data involves horizontal, radial strain about an open, cylindrical magma column. In this model, strain is inversely proportional to the square of the distance from the centre of the deformation. This strain pattern is probably confined to the immediate vicinity of the summit vents and is of a different nature lower down the volcano. Tiltmeter, precise levelling and distance measurement data collected over the period of a small flank eruption in January–March 1974 indicate that the eruption was fed by magma through a conduit from the summit reservoir system of the Chasm and Bocca Nuova. Inflation of the summit around the Northeast Crater, which had been measured since 1971, continued despite the flank eruption, and eruptive activity was resumed at the Northeast Crater in September 1974.     

The lobes of lava flows on Earth and Olympus Mons,Mars

The lobate distal margins of lava flows provide a useful source of morphological information on the rheology of the lava if the lobes are assumed to represent the arrest of free-flowing isothermal Bingham fluids on a slope. The widths of lobes are a more useful practical index than lobe thicknesses because they are about an order of magnitude larger and can be more accurately measured from aerial photographs and other remote images. Lobes do not suffer from the changes in morphology that channels undergo during the course of eruptions. A terrestrial data set of flow lobe and ancillary measurements from lavas throughout the range alkali olivine basalt to rhyolite shows some features that are predicted by the isothermal Bingham fluid model. These are correlation of width and thickness over more than two orders of magnitude and essentially no correlation of aspect ratio with slope. There is a positive correlation of lobe width with silica content of the lava. From a data set of measurements on lava flow lobes from the Martian volcano Olympus Mons the mean value of aspect ratio (0.07) was found to be significantly less than that for the terrestrial data set (0.19). Higher general levels of effusion rate on Olympus Mons are probably the factor responsible. After normalisation, lobe widths on Olympus Mons are found to be largely equivalent to those expected for terrestrial flows with andesitic/basaltic silica contents.     

Morphology,processes and evolution of two waterfalls near Cowra,New South Wales

The morphology and processes of formation and maintenance of waterfalls are more varied and complex than is suggested by the simple caprock‐undercutting model that is closely identified with Niagara Falls. The dominant process of retreat of two buttressed waterfalls near Cowra, NSW, seems to be failure along joint planes at the lips of the waterfalls. In the case of the larger of the two waterfalls, this process is significantly enhanced by the formation and subsequent destruction of potholes at the waterfall lip.     

New Zealand since 1984: Elite succession, income distribution and economic growth in a small trading economy

Four interrelated patterns of structural change in the New Zealand economy since 1980 are identified and analysed, against the backdrop of a growth rate which fell substantially behind the rest of the OECD in the late 1980s and early 1990s before recovering, but without catchup, from 1993. The changes discussed are: a shift in sharemarket capitalization from formerly-dominant productive activities in agriculture, manufacturing and construction to the current predominance of utilities, transport and finance; a sharp increase in overseas investors' share of the economic surplus, from around 20% to over half of post-tax corporate profits; a steady rise in international indebtedness at the same time as sovereign foreign-currency debt was eliminated; hence overseas debt was successfully privatized; a weakening of regulatory control over monopoly profits, opening the way for a surge of rent-seeking activity during the 1990s. The neoliberal reform programme has achieved fiscal and monetary sustainability, increased market flexibility, and insulated the economy against external shocks. At the same time it has led to denationalisation of economic surplus, ongoing current account deficits, and a significant diversion of resources from productive use into rent-seeking. This revised version was published online in July 2006 with corrections to the Cover Date.     

Numerical simulation on tendency mining fracture evolution characteristics of overlying strata and coal seams above working face with large inclination angle and mining depth

In order to master the tendency mining-fracture-evolution characteristics of overlying strata and coal seams above working face with large inclination angle and mining depth in mining process, the 1221 working face in Zhao mine is selected as the engineering background and a mathematical model is established. The displacement variation, stress and strain of overlying strata and coal seams are simulated by using ANSYS software. In the mining process, the movement characteristics, displacement variation laws and fracture evolution characteristics of overlying strata and coal seams above working face with large inclination angle and mining depth along inclination direction are discussed. Simulation results show that with the advance of working face, the fracture development of overlying strata and coal seams is larger and larger; the area of gob is gradually expanding and the transverse stress of overlying strata and coal seams is also expanding. Stress contour of overlying strata and coal seams at both ends of gob becomes denser and denser; the activity of the overlying strata and coal seams near the up-roadway side of the gob is violent. The pressure relief zone is formed in the upper part of the strata and the roof above the gob. Large inclination angle of coal seam results in larger supporting pressure in the underside of the gob and smaller supporting pressure in the upper side of the gob. Along the inclination direction of the working face, the pressure relief zone is mainly concentrated in the outlet roadway of the working face; the fracture development and strata separation are obvious, which offer good passage for gas flow and migration.     

The glutathione antioxidant system as a biomarker suite for the assessment of heavy metal exposure and effect in the grey mangrove, Avicennia marina (Forsk.) Vierh

Alterations in the glutathione antioxidant system and lipid peroxidation in Avicennia marina were studied under laboratory and field conditions. The activity of glutathione peroxidase (GPx) was found to respond to Zn exposure, and a significant positive relationship between leaf Zn concentration and GPx activity was observed after 96 h and 8 weeks. Lipid hydroperoxides increased proportionally with increasing leaf Zn concentration after 2 and 8 weeks, while no changes in total glutathione were observed. Induction of GPx at 96 h predicted effects at the individual level at a later time interval (reduced biomass at 8 weeks). Results from the field revealed that increasing leaf metal concentration (Zn, Cu or Pb) produced a proportional increase in GPx activity whereas lipid hydroperoxides and total glutathione were not affected. The utility of GPx as an early warning biomarker is suggested, since GPx activity increases in a dose-dependant fashion in response to accumulated leaf metals, and is predictive of later effects on growth.     

Modelling the lava dome extruded at Soufrière Hills Volcano, Montserrat, August 2005–May 2006: Part II: Rockfall activity and talus deformation

During many lava dome-forming eruptions, persistent rockfalls and the concurrent development of a substantial talus apron around the foot of the dome are important aspects of the observed activity. An improved understanding of internal dome structure, including the shape and internal boundaries of the talus apron, is critical for determining when a lava dome is poised for a major collapse and how this collapse might ensue. We consider a period of lava dome growth at the Soufrière Hills Volcano, Montserrat, from August 2005 to May 2006, during which a  100 × 10⁶ m³ lava dome developed that culminated in a major dome-collapse event on 20 May 2006. We use an axi-symmetrical Finite Element Method model to simulate the growth and evolution of the lava dome, including the development of the talus apron. We first test the generic behaviour of this continuum model, which has core lava and carapace/talus components. Our model describes the generation rate of talus, including its spatial and temporal variation, as well as its post-generation deformation, which is important for an improved understanding of the internal configuration and structure of the dome. We then use our model to simulate the 2005 to 2006 Soufrière Hills dome growth using measured dome volumes and extrusion rates to drive the model and generate the evolving configuration of the dome core and carapace/talus domains. The evolution of the model is compared with the observed rockfall seismicity using event counts and seismic energy parameters, which are used here as a measure of rockfall intensity and hence a first-order proxy for volumes. The range of model-derived volume increments of talus aggraded to the talus slope per recorded rockfall event, approximately 3 × 10³–13 × 10³ m³ per rockfall, is high with respect to estimates based on observed events. From this, it is inferred that some of the volumetric growth of the talus apron (perhaps up to 60–70%) might have occurred in the form of aseismic deformation of the talus, forced by an internal, laterally spreading core. Talus apron growth by this mechanism has not previously been identified, and this suggests that the core, hosting hot gas-rich lava, could have a greater lateral extent than previously considered.     

Forecast of Low Visibility and Fog from NCEP: Current Status and Efforts

Based on the visibility analysis data during November 2009 through April 2010 over North America from the Aviation Digital Database Service (ADDS), the performance of low visibility/fog predictions from the current operational 12?km-NAM, 13?km-RUC and 32?km-WRF-NMM models at the National Centers for Environmental Prediction (NCEP) was evaluated. The evaluation shows that the performance of the low visibility/fog forecasts from these models is still poor in comparison to those of precipitation forecasts from the same models. In order to improve the skill of the low visibility/fog prediction, three efforts have been made at NCEP, including application of a rule-based fog detection scheme, extension of the NCEP Short Range Ensemble Forecast System (SREF) to fog ensemble probabilistic forecasts, and a combination of these two applications. How to apply these techniques in fog prediction is described and evaluated with the same visibility analysis data over the same period of time. The evaluation results demonstrate that using the multi-rule-based fog detection scheme significantly improves the fog forecast skill for all three models relative to visibility-diagnosed fog prediction, and with a combination of both rule-based fog detection and the ensemble technique, the performance skill of fog forecasting can be further raised.     

Estimation of tephra volumes from sparse and incompletely observed deposit thicknesses

We present a Bayesian statistical approach to estimate volumes for a series of eruptions from an assemblage of sparse proximal and distal tephra (volcanic ash) deposits. Most volume estimates are of widespread tephra deposits from large events using isopach maps constructed from observations at exposed locations. Instead, we incorporate raw thickness measurements, focussing on tephra thickness data from cores extracted from lake sediments and through swamp deposits. This facilitates investigation into the dispersal pattern and volume of tephra from much smaller eruption events. Given the general scarcity of data and the physical phenomena governing tephra thickness attenuation, a hybrid Bayesian-empirical tephra attenuation model is required. Point thickness observations are modeled as a function of the distance and angular direction of each location. The dispersal of tephra from larger well-estimated eruptions are used as leverage for understanding the smaller unknown events, and uncertainty in thickness measurements can be properly accounted for. The model estimates the wind and site-specific effects on the tephra deposits in addition to volumes. Our technique is exemplified on a series of tephra deposits from Mt Taranaki (New Zealand). The resulting estimates provide a comprehensive record suitable for supporting hazard models. Posterior mean volume estimates range from 0.02 to 0.26 km ³. Preliminary examination of the results suggests a size-predictable relationship.