Perception of landslides risk and responsibility: a case study in eastern Styria, Austria

This paper presents a case study about the perception of landslide risk. Following a major set of landslides in the eastern part of Austria in June 2009, we surveyed local experts, residents who had suffered losses from the landslides, and others living in the affected communities. Overall, the risk perception was significantly higher among those who had been personally affected by a landslide, had knowledge of the geology in the study region, had been affected by another natural hazard, or spent a lot of time outdoors and in touch with nature. Non-experts viewed natural factors as the main causes for the occurrence of landslides, while experts viewed anthropogenic factors as more important. Likewise, non-experts placed a greater emphasis on hard measures (such as retaining walls) to reduce the risk, whereas the experts tended to focus on better information and land-use planning. In terms of responsibility for mitigative actions, a majority of inhabitants believed that public authorities should undertake most of the costs, whereby those who had personal experience with landslides were more likely to favor the government paying for it.     

The Distribution of Craters Within Craters

Photometric correction is a necessary step in planetary image pre-processing since the images of planetary surfaces are acquired by orbiting spacecraft at various observational geometries. In this study, visible (748 nm) and near-infrared (948 nm) bands of Hyper Spectral Imager (HySI) onboard Chandrayaan-1 have been used to derive a preliminary photometric correction for lunar data. The purpose of the proposed photometric correction for HySI is to convert observations taken at solar incidence (i), sensor emission (e), and the solar phase angles (α) to a fixed geometry by applying i?=?α?=?30° and e?=?0° to each image. The Lommel–Seeliger function was used to model the lunar limb darkening effect, while topography data from the merged Digital Elevation Model of Lunar Reconnaissance Orbiter—Lunar Orbiter Laser Altimeter (LRO-LOLA) and SELENE Terrain Camera (TC) was used to correct local topographic effects. Data from Moon Mineralogy Mapper (M³), SELENE Multiband Imager (MI) and Clementine Ultraviolet and Visible Camera (UV/VIS) were also used to compare radiance, reflectance and phase functions derived from HySI. Our analysis reveals that HySI is darker than M³ primarily due to low surface radiance conditions observed by HySI. The derived phase functions for the two HySI bands indicate a good correlation between the derived reflectance and phase angle as well as with the phase functions derived for the empirically corrected M³ data. This approach led to the derivation of a photometric correction for maria regions. Finally, it is expected that the proposed correction would be applicable to all HySI images covering the lunar mare region.

     

Utility of the 2-D Multi-Electrode Resistivity Imaging Technique in Groundwater Exploration in the Voltaian Sedimentary Basin, Northern Ghana

Guinea worm and other water borne diseases associated with untreated surface water use have necessitated that communities are supplied with groundwater in the Northern Region of Ghana. The Electrical Resistivity Survey (ERS) method is one of the common geophysical survey techniques used for borehole siting in Ghana. Various groundwater exploration programs have utilized it by employing the four electrode system. However, the ERS has not been able to locate potential borehole sites successfully in the Voltaian Sedimentary Basin (VSB) in the Northern Region of Ghana although it has been successful in other geological formations. Unsatisfactory results obtained from the employment of the ERS system in the VSB therefore necessitated an experiment with the 2-D Multi-Electrode Resistivity Imaging (2-D MERI) technique. Field results show that the 2-D MERI is a robust and efficient technique: an improvement on the four electrode ERS system in terms of amount and quality of data obtained. The 2-D MERI interpretations were confirmed with a much improved borehole drilling success rate of 60% compared to 38% obtained using the ERS within the mudstone and shale formations. The 2-D MERI also indicated that very low resistivity layers in the VSB may not necessarily be good targets for borehole drilling and the generally held notion that groundwater cannot be found at depths more than 25 m is no longer tenable.     

Endogenous growth in channelized komatiite lava flows: evidence from spinifex-textured sills at Pyke Hill and Serpentine Mountain,Western Abitibi Greenstone Belt,Northeastern Ontario,Canada

Spinifex-textured sills (i.e., veins) characterized by komatiitic magmas that have intruded their own volcanic-piles have long been recognized. For instance, in the early 1970s, Pyke and coworkers, in their classic work at Pyke Hill in Munro Township, noted that not all spinifex-bearing ultramafic rocks formed as lava flows, rather some were clearly emplaced as small dikes and sills. Several hypotheses have been proposed to explain spinifex-textured sills: intrusion into a cold host, filter pressing, or drainage of residual liquid. However, these do not satisfactorily explain the phenomenon. Field and petrographic observations at Pyke Hill and Serpentine Mountain demonstrate that spinifex-bearing komatiite sills and dikes were emplaced during channel inflation processes when new magma was intruded into a cooler, semi-consolidated but permeable cumulate material. Komatiitic liquids were intruded into the olivine cumulate rocks near the boundary between the spinifex and the cumulate zones of well-organized to organized komatiite flows. Spinifex-textured sills are generally tabular in morphology, stacked one above another, with curviplanar contacts sub-parallel to stratigraphy. Some sills exhibit complex digitated apophyses. Thinner sills typically have a random olivine spinifex texture similar, though generally composed of coarser crystals, to that of komatiite lava flows. Thicker sills exhibit more complex organization of their constituent crystals characterized by zones of random olivine spinifex, overlying zones of organized coarse spinifex crystals similar to those found in lava flows. They have striking coarse dendritic spinifex zones composed of very large olivine crystals, up to several centimetres long and up to 1 cm wide that are not observed in lava flows. Typically, at the sill margins, the cumulate material of the host flow is composed of euhedral to subhedral olivine crystals that are larger than those distal to the contact. Many of these margin-crystals have either concentric overgrowth shells or dendritic olivine overgrowths that grew from the cumulate-sill contact toward the sill interior. The dendrites grew on pre-existing olivine cumulate at the contact in response to a sharp temperature gradient imposed by the intrusion of hot material, whereas the concentric overgrowths formed as new melt percolated into the unconsolidated groundmass of the host-flow cumulate material. Spinifex-textured sills and dikes occur in well-organized to organized flows that are interpreted to have formed by “breakouts” above and peripheral to lava pathways (channels/conduits) as a result of inflation that accompanied voluminous komatiitic eruptions responsible for the construction and channelization of komatiitic flow fields. The spinifex-textured dikes and sills represent komatiitic lava that was originally emplaced into the channel roof during periods of episodic inflation that resulted in lava breakouts and was subsequently trapped in the “roof rocks” during periods of channel deflation. Accordingly, the occurrence of spinifex-textured sills and dikes may indicate proximity to, and aid in the identification and delineation of lava channel-ways that could potentially host Ni–Cu–(PGE) mineralization within komatiitic lava flow-fields.     

Petrogenesis of the Greenhills Complex,Southland, New Zealand: magmatic differentiation and cumulate formation at the roots of a Permian island-arc volcano

A Permian (~265 Ma) intrusive complex which formed as a magmatic feeder reservoir to an immature island-arc volcano is fortuitously exposed in southern New Zealand. Known as the Greenhills Complex, this intrusion was emplaced at shallow crustal levels and consists of two layered bodies which were later intruded by a variety of dykes. Cumulates, which include dunite, olivine clinopyroxenite, olivine gabbro, and hornblende gabbro-norite, are related products of parent-magma fractionation. Both primary (magmatic) and secondary platinum-group minerals occur within dunite at one locality. Using the composition of cumulus minerals, mafic dykes and melt inclusions, we have determined that the parent magmas of the complex were hydrous, low-K island-arc tholeiites of ankaramitic affinities. Progressive magmatic differentiation of this parent magma generated fractionated melt of high-alumina basalt composition which is now preserved only as dykes which cut the Complex. Field evidence and cumulus mineral profiles reveal that the magma chambers experienced turbulent magmatic conditions during cumulate-rock formation. Recharge of the chambers by primitive magma is likely to have coincided with eruption of residual melt at the surface. Similar processes are inferred to account for volcanic-rock compositions in other parts of this arc terrane and in modern island-arc systems.     

Average chemical composition of the lunar surface

The available data on the chemical composition of the lunar surface at eleven sites (3 Surveyor, 5 Apollo and 3 Luna) are used to estimate the amounts of principal chemical elements (those present in more than about 0.5% by atom) in average lunar surface material. The terrae of the Moon differ from the maria in having much less iron and titanium and appreciably more aluminum and calcium.Paper dedicated to Prof. Harold C. Urey on the occasion of his 80th birthday on 29 April 1973.     

A clinoenstatite-bearing cumulate Olivine Pyroxenite from Howqua,Victoria

The Howqua Olivine Pyroxenite of eastern Victoria, Australia, intrudes a metamorphosed sequence of Cambrian high-Mg lavas. It crystallized an unusual mineral assemblage: Cr-rich magnesiochromite, olivine (Fo₉₄), and protoenstatite (now inverted to polysynthetically-twinned clinoenstatite). Residual liquid crystallized strongly-zoned interstitial pyroxenes followed by pargasite. Pargasite, often showing quench habit, crystallized in interstitial glass which is now altered to serpentine.The extremely refractory nature of the cumulus phases indicates a very high temperature of crystallization for liquidus olivine and chromite from a high-MgO, low-Al₂O₃ parent liquid similar in some respects to Archaean peridotitic komatiites. The suggested origin by hydrous melting of depleted mantle peridotite, plus other compositional and mineralogical similarities (especially the olivine-liquid reaction producing protoenstatite) indicate that the parent magma of the Howqua Olivine Pyroxenite had many features in common with the high-SiO₂, high-MgO clinoenstatite-bearing boninitic lavas of the Western Pacific. It is interpreted as a more extreme melt with affinities to boninite and it demonstrates that ultramafic magmas existed in the Cambrian.     

Determination of water component age in ocean models: application to the fate of North Atlantic Deep Water

A method allowing the calculation of both concentration and age of an individual water component is used to examine the penetration and fate of North Atlantic Deep Water (NADW) in a global ocean model. The method is consistent with the recent theory of water component age by Delhez et al. Its application in ocean models is straightforward and involves specification of two ideal tracers, and its efficacy is verified here via comparison with water component ages obtained by a second method, involving the time history of a single ideal tracer, and whose application is rather more restricted. Age estimates by the two methods are compared in the case of an interior ocean source region (suitable for marking the model's NADW, and forming the main focus of the study) and in the case of a ocean surface source region (featuring high density surface water in the far Northern Atlantic). The concentration and age of NADW are determined for two versions of the model, differing only in the inclusion or exclusion of isoneutral diffusion. The age and, especially, the concentration of NADW in the deep Southern, Indian and Pacific Oceans are significantly lower in the version with isoneutral diffusion. Both versions indicate that most of the NADW ultimately reaches the surface in the model Southern Ocean.