Evolution of the late Pleistocene Mojanda–Fuya Fuya volcanic complex (Ecuador), by progressive adakitic involvement in mantle magma sources

The Mojanda–Fuya Fuya Volcanic Complex consists of two nearby volcanoes, Mojanda and Fuya Fuya. The older one, Mojanda volcano (0.6 to 0.2 Ma), was first constructed by andesites and high-silica andesites forming a large stratovolcano (Lower Mojanda). This edifice was capped by a basaltic andesite and andesitic cone (Upper Mojanda), which collapsed later to form a 3-km-wide summit caldera, after large phreatomagmatic eruptions. The Lower Fuya Fuya edifice was constructed by the extrusion of viscous Si-rich andesitic lavas and dacitic domes, and the emission of a thick sequence of pyroclastic-flow and fallout deposits which include two voluminous rhyolitic layers. An intermediate construction phase at Fuya Fuya is represented by a mainly effusive cone, andesitic in composition (San Bartolo edifice), the construction of which was interrupted by a major sector collapse in the Late Pleistocene. Finally, a complex of thick siliceous lavas and domes was emplaced within the avalanche amphitheatre, forming the Upper Fuya Fuya volcanic centre. This paper shows that the general evolution from an effusive to an explosive eruptive style is related to a progressive adakitic contribution to the magma source. Although all the rocks of the complex are included in the medium-K field of continental arcs, the Fuya Fuya suite (61–75 wt.% SiO₂) shows depletion in Y and HREE and high Sr/Y and La/Yb values, compared to the less silicic Mojanda suite (55–66.5 wt.% SiO₂). The Mojanda calc-alkaline suite was generated by partial melting of an adakite-metasomatised mantle source that left a residue with 2% garnet, followed by fractional crystallization of dominant plagioclase + pyroxene + olivine at shallow, intra-crustal depths. For Fuya Fuya, geochemical and mineralogical data suggest either (1) partial melting of a similar metasomatised mantle with more garnet in the residue (4%), followed by fractional crystallization involving plagioclase, amphibole and pyroxene, or (2) mixing of mafic mantle-derived magma from the Mojanda suite and slab melts, followed by the same fractional crystallization process.     

Estimating overland flow erosion capacity using unit stream power

Soil erosion caused by water flow is a complex problem. Both empirical and physically based approaches were used for the estimation of surface erosion rates. Their applications are mainly limited to experimental areas or laboratory studies. The maximum sediment concentration overland flow can carry is not considered in most of the existing surface erosion models. The lack of erosion capacity limitation may cause over estimations of sediment concentration. A correlation analysis is used in this study to determine significant factors that impact surface erosion capacity. The result shows that the unit stream power is the most dominant factor for overland flow erosion which is consistent with experimental data. A bounded regression formula is used to reflect the limits that sediment concentration cannot be less than zero nor greater than a maximum value. The coefficients used in the model are calibrated using published laboratory data. The computed results agree with laboratory data very well. A one dimensional overland flow diffusive wave model is used in conjunction with the developed soil erosion equation to simulate field experimental results. This study concludes that the non-linear regression method using unit stream power as the dominant factor performs well for estimating overland flow erosion capacity.     

Comments on “Two-dimensional concentration distribution for mixing-controlled bioreactive transport in steady-state” by O.A. Cirpka and A.J. Valocchi

In this comment we present a re-analysis of the analytical solution presented by Cirpka and Valocchi for steady-state concentrations of dissolved bioreactive compounds and bacterial biomass in porous media. We discuss the validity range of the analytical solution. In particular, the criterion used to determine the sustainability of biomass is revisited. This re-analysis shows that the ω$\omega$ criterion used by Cirpka and Valocchi is only a necessary but not a sufficient criterion to determine the bioreactive zones. As a consequence, the analytical solution does not provide the exact distribution of compounds throughout the domain, but can serve as upper or lower boundaries for species concentrations at a given location. These conclusions are supported by the simulation results obtained from an established reactive transport model.     

Active Galactic Nuclei

F11 Jets, supernovae, gammabursts – more light for theory? F35 A Direct Comparison of the QSO Samples from VPMS and SDSS F36 Gravitational Microlensing Simulations and Ensemble Broad‐Band Variability of the QSOs from VPMS F42 Luminosity function of low redshift quasars F43 Star Formation around Active Galactic Nuclei – Results from near infrared observations F58 High‐Redshift Quasars as Probes of Early Star Formation F66 On the dust emission of Seyfert nuclei F72 Propagation of Very Light MHD Jets F78 Giant Outflows in MassiveHigh‐z Radio Galaxies: Direct Evidence for AGNFeedback in the Early Universe F89 Lowfrequency mapping of ‘normal’ FR II radio galaxies: Resolving the puzzle of X‐shaped radio sources F90 Nature of X‐shaped radio sources: A statistical approach F100 Cosmological growth of Supermassive Black Holes: constraints on kinetic and radiative energy feedback F107 Molecular Tori in AGN F136 Electron‐Ion Recombination Rate Coefficients of Iron M‐Shell Ions for X‐Ray Astronomy F139 Hydrodynamic models of obscuring tori F145 The unique BL Lac Object S5 0716+714 F158 On the Cluster Environment of the BL Lac Object OJ 287 F179 The circumnuclear dust in nearby AGN resolved by mid‐infrared interferometry F184 NIR‐imaging of SDSS BL Lac objects F190 Blazar Observations in the TeV energy range with the MAGIC Telescope F198 Gas Inflow Rates in Nearby AGN Galaxies F202 Two zone SSC model for blazar jets F215 Long‐termVHE γ ‐ray monitoring of bright blazars with a dedicated telescope F218 Long termmonitoring of bright TeV Blazars with the MAGIC telescope F220 Fifteen Blazars in Very‐High Energy Gamma Rays: A Comparative Study F229 Numerical calculation of blazar spectra. Application to 1 ES 1218+30.4 F230 Blazar spectral energy distributions corrected for gamma ray attenuation F240 Observation of PG 1553+113 with the MAGIC Telescope F243 VHE Gamma‐Ray Flare of PKS2155‐304 detected by the MAGIC telescope F245 Observations of 3C279 with the MAGIC Telescope F258 Diffraction limited near infrared imaging spectroscopy of the NLR of NGC4151     

Climate impacts of environmental degradation in Sudan

There exists an impressive amount of work for Sudan showing the anthropogenic degradation of natural vegetation cover. However, there are few examples of consequent climatic changes in literature. This work, thus, seeks to assess such effects of environmental forcing on various climatic patterns over the past few decades. Within the frame of the present analysis, the results are quite striking and are in concordance with scientific contentions that such land degradation could result in climatic modification. Higher temperature and less rainfall, sunshine duration and global radiation have been noticed. Evapotranspiration has responded more to the warming and drying conditions, thus showed signs of increasing rates, especially during the wet season. However, the extent of increase seems to have been suppressed by the decrease in sunshine duration and solar radiation as well as the inconsistent behaviour of wind speed. Changes in the variability of the within-year monthly observations have also occurred, thus suggesting an increase in the occurrence of extremes. The observed climatic modification in the country has exaggerated the insidious drought conditions. The present findings are hoped to contribute to our understanding of the effects of environmental problem and assist in considering policy responses. This revised version was published online in July 2006 with corrections to the Cover Date.     

Coastal erosion vs riverine sediment discharge in the Arctic Shelf seas

This article presents a comparison of sediment input by rivers and by coastal erosion into both the Laptev Sea and the Canadian Beaufort Sea (CBS). New data on coastal erosion in the Laptev Sea, which are based on field measurements and remote sensing information, and existing data on coastal erosion in the CBS as well as riverine sediment discharge into both the Laptev Sea and the CBS are included. Strong regional differences in the percentages of coastal erosion and riverine sediment supply are observed. The CBS is dominated by the riverine sediment discharge (64.45᎒⁶ t a^-1) mainly of the Mackenzie River, which is the largest single source of sediments in the Arctic. Riverine sediment discharge into the Laptev Sea amounts to 24.10᎒⁶ t a^-1, more than 70% of which are related to the Lena River. In comparison with the CBS, the Laptev Sea coast on average delivers approximately twice as much sediment mass per kilometer, a result of higher erosion rates due to higher cliffs and seasonal ice melting. In the Laptev Sea sediment input by coastal erosion (58.4᎒⁶ t a^-1) is therefore more important than in the CBS and the ratio between riverine and coastal sediment input amounts to 0.4. Coastal erosion supplying 5.6᎒⁶ t a^-1 is less significant for the sediment budget of the CBS where riverine sediment discharge exceeds coastal sediment input by a factor of ca. 10.     

半地堑盆地演化机制的粘弹塑数值模拟

利用新近完成的粘弹塑构造模拟软件包对盆地的动力学演化进行了一系列模拟。文中主要概述不同厚度的上地壳中由高角度平面正断层界定的半地堑盆地的演化模拟。模拟时上地壳被考虑成具有Byerlee型强度包络 ,并且位于无粘性基底之上 ,盆地中由密度比地壳密度小的沉积物充填。计算了以一定增量逐渐拉伸上地壳层时各个阶段的非静岩应力 (Nonlitho staticstress)、塑性破裂 (Plasticfailure)分布及挠曲剖面 (Flexureprofile)。塑性变形使得有效弹性厚度减小。到切穿破裂出现以前 ,断层断距一直增加 ,之后 ,断距基本停止增加。所以 ,地壳强度使沉降量和隆升量均有极限。上地壳层厚度和沉积物密度是控制盆地宽度和极限深度的两个重要因素 ,上地壳层厚度增加或者沉积物密度加大都使盆地宽度和深度增大。模拟结果可以解释一些大陆裂谷盆地的宽度和沉积深度。     

Theoretical Signature of Solar Meridional Flow in Global Seismic Data

Approximate expressions are derived for the perturbations in solar p- and f-mode oscillation eigenfunctions, due to large-scale, meridional flows which are symmetric about the equator. The essential signature of the perturbed eigenfunctions in global helioseismic data is derived and the prospects for detecting meridional flow using global seismic techniques are discussed.     

Preliminary study on the dissolved and colloidal organic carbon in the Zhujiang River estuary

ＩＮＴＲＯＤＵＣＴＩＯＮＥｓｔｕａｒｉｅｓｃｏｍｐｒｉｓｅａｍａｊｏｒｂｉｏｇｅｏｃｈｅｍｉｃａｌｉｎｔｅｒｆａｃｅｃｏｎｎｅｃｔｉｎｇｔｈｅｌａｎｄａｎｄｔｈｅｓｅａ (Ｍａｎ ｔｏｕｒａ,1 987) .Ｔｈｅｂｅｈａｖｉｏｒａｎｄｆａｔｅｏｆａｐａｒｔｉｃｕｌａｒｒｉｖｅｒ ｂｏｒｎｅｓｕｂｓｔａｎｃｅｉｎｔｒｏｄｕｃｅｄｉｎｔｏａｎｅｓｔｕａｒｙｉｓｄｅｔｅｒｍｉｎｅｄｔｏａｌａｒｇｅｅｘｔｅｎｔｂｙｔｈｅｂｉｏｇｅｏｃｈｅｍｉｃａｌｐｒｏｐｅｒｔｉｅｓｏｆｔｈｅｓｕｂｓｔａｎｃｅａｓｗｅｌｌａｓｐ…