Evidence of a shallow magma intrusion beneath the NE Rift system of Mt. Etna during 2013

Continuous GPS (CGPS) data, collected at Mt. Etna between April 2012 and October 2013, clearly define inflation/deflation processes typically observed before/after an eruption onset. During the inflationary process from May to October 2013, a particular deformation pattern localised in the upper North Eastern sector of the volcano suggests that a magma intrusion had occurred a few km away from the axis of the summit craters, beneath the NE Rift system. This is the first time that this pattern has been recorded by CGPS data at Mt. Etna. We believe that this inflation process might have taken place periodically at Mt. Etna and might be associated with the intrusion of batches of magma that are separate from the main feeding system. We provide a model to explain this unusual behaviour and the eruptive regime of this rift zone, which is characterised by long periods of quiescence followed by often dangerous eruptions in which vents can open at low elevation and thus threaten the villages in this sector of the volcano.     

An application of EMS98 in a medium-sized city: The case of L��Aquila (Central Italy) after the April 6, 2009 Mw 6.3 earthquake

This paper describes the damage survey in the city of L??Aquila after the 6 April 2009 earthquake. The earthquake, whose magnitude and intensity reached Mw?=?6.3 and Imax?=?9?C10 MCS, struck the Abruzzi region of Central Italy producing severe damage in L??Aquila and in many villages along the Middle Aterno River valley. After the event, a building-to-building survey was performed in L??Aquila downtown aiming to collect data in order to perform a strict evaluation of the damage. The survey was carried out under the European Macroseismic Scale (EMS98) to evaluate the local macroseismic intensity. This damage survey represents the most complex application of the EMS98 in Italy since it became effective. More than 1,700 buildings (99% of the building stock) were taken into account during the survey at L??Aquila downtown, highlighting the difficult application of the macroseismic scale in a large urban context. The EMS98 revealed itself to be the best tool to perform such kind of analysis in urban settings. The complete survey displayed evidence of peculiar features in the damage distribution. Results revealed that the highest rate of collapses occurred within a delimited area of the historical centre and along the SW border of the fluvial terrace on which the city is settled. Intensity assessed for L??Aquila downtown was 8?C9 EMS.     

Ordinary chondrite-related giant (>800 μm) cosmic spherules from the Transantarctic Mountains, Antarctica

In order to identify the parent bodies of cosmic spherules (melted micrometeorites) with porphyritic olivine (PO) and cryptocrystalline (CC) textures, we measured the oxygen isotopic composition of 15 giant (>800 μm) cosmic spherules recovered in the Transantarctic Mountains, Antarctica, with IR-laser fluorination/mass spectrometry, and we conducted a characterization of their petrographic and magnetic properties. Samples include 6, 8 and 1 spherules of PO, CC and barred olivine (BO) textural types, respectively. Eleven spherules (∼70% of the total: 4/6 PO and 6/8 CC, and the BO spherule) are related to ordinary chondrites based on oxygen isotopic compositions. Olivines in ordinary chondrite-related spherules have compositions Fa_8.5-11.8, they are Ni-poor to Ni-rich (0.04-1.12 wt.%), and tend to be richer in CaO than other spherules (0.10-0.17 wt.%). Ordinary-chondrite related spherules also have high magnetite contents (∼2-12 wt.%). One PO and one CC spherules are related to previously identified ¹⁷O-enriched cosmic spherules for which the parent body is unknown. One CC spherule has an oxygen isotopic signature relating it to CM/CR carbonaceous chondrites. The majority of PO/CC cosmic spherules derive from ordinary chondrites; this result exemplifies how the texture of cosmic spherules is not only controlled by atmospheric entry heating conditions but also depends on the parent body, whether be it through orbital parameters (entry angle and velocity), or chemistry, mineralogy, or grain size of the precursor.     

Cooling by grains and H2 in collapsing clouds of different metallicities

Computations of the cooling by grains and by H₂ molecules are carried out and applied to different stages of cloud collapse during the isothermal phase. Clouds of 10⁶ M of different metallicites are considered, with the purpose of obtaining a relation between metallicity and importance of grain cooling relative to H₂ cooling. Our results show that grain cooling dominates over H₂ cooling for metallicities [M/H] > -4.0, in the absence of external UV field.     

Landslide susceptibility modeling in a landslide prone area in Mazandarn Province,north of Iran: a comparison between GLM,GAM, MARS,and M-AHP methods

Theoretical and Applied Climatology - Landslides are identified as one of the most important natural hazards in many areas throughout the world. The essential purpose of this study is to compare...     

XMM–Newton observations of the black hole X-ray transient XTE J1650–500 in quiescence

We report the result of an XMM–Newton observation of the black hole X-ray transient XTE J1650–500 in quiescence. The source was not detected, and we set upper limits on the 0.5–10 keV luminosity of  0.9–1.0 × 10³¹ erg s⁻¹  (for a newly derived distance of 2.6 kpc). These limits are in line with the quiescent luminosities of black hole X-ray binaries with similar orbital periods (∼7–8 h).     

Megacrysts and mafic–ultramafic xenolith-bearing ignimbrites from Sirwa Volcano, Morocco: phase petrology and thermobarometry

Summary A suite of clinopyroxene and amphibole megacrysts and mafic–ultramafic xenoliths are present in ignimbritic rocks of trachybasaltic–andesitic composition from the Sirwa volcanic district, Morocco. The stumpy prismatic and sometimes euhedral clinopyroxene megacrysts are Ti–Al-rich diopsides with mg values in the range 0.82–0.87 and Ca/(Ca + Mg) ratios in the range 0.53–0.54. The prismatic, elongated amphibole megacrysts are calcic kaersutites–kaersutites with a narrow mg range (0.66–0.68). The xenoliths are represented by gabbroic and pyroxenitic types. In the gabbroic xenoliths two distinct textural types can be distinguished: medium-sized granular and banded. The granular type is characterized by the mineral assemblage Pl + Amph + Spl + Ilm + Ap. The banded type is distinct for the absence of Ilm and the presence of Cpx and Opx and shows alternating bands enriched in Pl and Amph, respectively. The megacrysts and, probably, the xenoliths are considered not cognate with the present host rocks since the calculated liquids in equilibrium with clinopyroxene and amphibole megacrysts over a wide range of physical conditions have different trace and rare earth element contents. The observed phase relations and thermobarometric calculations indicate that the megacrysts and xenoliths crystallized from their parent melts at P ≥ 10 kbar and T ≤ 1160 °C, i.e., in the upper mantle or near the crust-mantle boundary. A deep ( ≥ 30 km) magmatic chamber, where the megacrysts and xenoliths originated, and a shallow volcanic chamber, energetically activated up to explosive conditions by injection of deep-originated melts, is suggested to explain the occurrence of high-pressure megacrysts and xenoliths in the Sirwa volcanic explosive products. Received October 8, 2000; revised version accepted September 9, 2001     

Geochemical evidence of hydrothermal recharge in Lake Baringo,central Kenya Rift Valley

Lake Baringo, a freshwater lake in the central Kenya Rift Valley, is fed by perennial and ephemeral rivers, direct rainfall, and hot springs on Ol Kokwe Island near the centre of the lake. The lake has no surface outlet, but despite high evaporation rates it maintains dilute waters by subsurface seepage through permeable sediments and faulted lavas. New geochemical analyses (major ions, trace elements) of the river, lake, and hot spring waters and the suspended sediments have been made to determine the main controls of lake water quality. The results show that evaporative concentration and the binary mixing between two end members (rivers and thermal waters) can explain the hydrochemistry of the lake waters. Two zones are recognized from water composition. The southern part of the lake near sites of perennial river inflow is weakly influenced by evaporation, has low total dissolved species (TDS), and has a seasonally variable load of mainly detrital suspended sediments. In contrast, waters of the northern part of the lake show evidence for strong evaporation (TDS of up to eight times inflow). Authigenic clay minerals and calcite may be precipitating from those more concentrated fluids. The subaerial hot‐spring waters have a distinctive chemistry and are enriched in some elements that are also present in the lake water. Comparison of the chemical composition of the inflowing surface waters and lake water shows (1) an enrichment of some species (HCO₃^?, Cl, SO₄^2?, F, Na, B, V, Cr, As, Mo, Ba and U) in the lake, (2) a depletion in SiO₂ in the lake, and (3) a possible hydrothermal origin for most F. The rare earth element distribution and the F/Cl and Na/Cl ratios give valuable information on the rate of mixing of the river and hydrothermal fluids in the lake water. Calculations imply that thermal fluids may be seeping upward locally into the lake through grid‐faulted lavas, particularly south of Ol Kokwe Island. Copyright © 2006 John Wiley & Sons, Ltd.