What makes flank eruptions? The 2001 Etna eruption and its possible triggering mechanisms

Most flank eruptions within a central stratovolcano are triggered by lateral draining of magma from its central conduit, and only few eruptions appear to be independent of the central conduit. In order to better highlight the dynamics of flank eruptions in a central stratovolcano, we review the eruptive history of Etna over the last 100 years. In particular, we take into consideration the Mount Etna eruption in 2001, which showed both summit activity and a flank eruption interpreted to be independent from the summit system. The eruption started with the emplacement of a ~N-S trending peripheral dike, responsible for the extrusion of 75% of the total volume of the erupted products. The rest of the magma was extruded through the summit conduit system (SE crater), feeding two radial dikes. The distribution of the seismicity and structures related to the propagation of the peripheral dike and volumetric considerations on the erupted magmas exclude a shallow connection between the summit and the peripheral magmatic systems during the eruption. Even though the summit and the peripheral magmatic systems were independent at shallow depths (<3 km b.s.l.), petro-chemical data suggest that a common magma rising from depth fed the two systems. This deep connection resulted in the extrusion of residual magma from the summit system and of new magma from the peripheral system. Gravitational stresses predominate at the surface, controlling the emplacement of the dikes radiating from the summit; conversely, regional tectonics, possibly related to N-S trending structures, remains the most likely factor to have controlled at depth the rise of magma feeding the peripheral eruption.     

The three screen doors: can marine "protected" areas be effective?

The great majority of marine protected areas (MPAs) fail to meet their management objectives. So MPAs can be effective conservation tools, we recommend two paradigm shifts, the first related to how they are located and the second related to how they are managed. MPAs are unlikely to be effective if they are located in areas that are subject to numerous, and often uncontrollable, external stressors from atmospheric, terrestrial, and oceanic sources, all of which can degrade the environment and compromise protection. MPA effectiveness is also limited by low institutional and community capacity for management and inappropriate size with respect to ecological needs. In particular, the check list approach to management does not ensure that key threats are dealt with, or that management expenditures provide a quantifiable return. We recommend a business planning approach to MPA management, in which managers focus on the viability of the management system, i.e., the ability of the MPA to provide ecological goods and services to its target users over the long term.     

The Results and Comparison of "Logical-Tree" Seismic Zoning in the Panxi Area

On the basis of the technological route of seismic hazard analysis,the methods for determining seismicity parameters,such as b value,annual occurrence rate,and the seismic spatial distribution function,are discussed.Then,the seismic intensity zoning in Panxi area in Southwest China is carried out by applying the "logical-tree,"which is made up of multi-parameter schemes.It is clearly shown from the results that seismic intensity zoning is influenced by many uncertain factors and it is necessary to seek a certain balance between seismic safety and investment interest and a good way,with the present limited knowledge level,to obtain seismic intensity zoning is through the "logical-tree" method.     

Research Project "Analysis on Changes in Runoff and Sediment Load in The Yellow River" completed for The Ministry of Water Rsources PRC

This large-scale research project was sponsored by the Foundation of Changes inRunoff and Sediment Load in The Yellow River, Ministry of Water Resources PRC. Since1970's evident reduction in runoff and sediment load in the Yellow River took place. Considering such changes might bring about profound consequences to the development of thewhole Yellow River, a special foundation to study the future trend of changes in runoff andsediment load was set up by the Ministry of Water Resources f…     

Water contaminated by fresh tephra as a natural hazard factor: The 2008–2009 eruption of Koryakskii Volcano,Kamchatka

This study is the first to show, using data from the eruption of Koryakskii Volcano, Kamchatka that began in December 2008 and continued through 2009 that the water in permanent and temporary streams that start on the slopes of the volcanic cone and in temporary lakes when contaminated with fresh tephra is a specific hazard factor related to long-continued hydrothermal-phreatic eruptions on that volcano. This water is characterized by increased acidity (pH 4.1–4.35) and large amounts (up to 50–100 cm³/liter) of solid suspension and is unfit for drinking and irrigation. When combined with tephra, it probably produced mass destruction of a number of animals who lived on the slopes and at the base of the volcano. The water contaminated with tephra is an important component of the atmospheric mud flows occurring on Koryakskii Volcano; for several future years it will be a potential source for enhancing the acidity of ground water in the volcanic edifice.     

Frequency response of tiltmeters and tidal factor

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Research Project "Environmental Evolution of The Yellow River Catchment and Its Runoff and Sediment Load" Completed for The National Natural Science Foundation of Chian

This large-scale research project was sponsored by the National Natural Science Foundation of China and managed jointly by Institute of Geography and Yellow River ConservancyCommission. About 140 scientists and engineers from 19 research institutes and universitiesparticipated in the study, lasting four and half years. The multi-disciplinary researches involve geography, paleoclimatology, water science, soil erosion, oceanology ... etc. Integratedapproaches were used including field invest…     

What surrounds the stars?

Helen Walker summarizes the RAS discussion meeting, 14 January 2000, on the material around main-sequence and post-main-sequence stars.     

What is suspended sediment?

Suspended sediment is conventionally regarded as that sediment transported by a fluid that it is fine enough for turbulent eddies to outweigh settling of the particles through the fluid. Early work in the fluvial field attributed suspension to turbulence, and led to the notion of a critical threshold for maintaining sediment in suspension. However, research on both turbulence structures and the interactions between suspended sediment and bedforms in rivers has shown a more complex story and, although there appear to have been no studies of the impact of bedforms on aeolian suspended sediment concentrations, turbulent flow structures and transport rates of saltating particles have been shown to be affected. This research indicates that suspended sediment neither travels with the same velocity as the flow in which it is suspended, nor is it likely to remain in suspension in perpetuity, even under conditions of steady flow or in unsteady flow the where dimensionless critical threshold is permanently exceeded. Rather, like bedload, it travels in a series of hops, and is repeatedly deposited on the bed where it remains until it is re‐entrained. Is there, therefore, a qualitative difference between suspended and saltating sediment, or is it just a quantitative difference in the size of the jump length and the frequency of re‐entrainment? It is our contention that the distinction of suspension as a separate class of sediment transport is both arbitrary and an unhelpful anthropocentric artefact. If we recognize that sediment transport is a continuum and applies to any fluid medium rather than split into different “processes” based on arbitrary thresholds and fluids, then recognizing the continuity will enable development of an holistic approach sediment transport, and thus sediment‐transport models that are likely to be viable across a wider range of conditions than hitherto. Copyright © 2015 John Wiley & Sons, Ltd.     

What is DMO coverage?

'Coverage' or 'fold' is defined as the multiplicity of common-midpoint (CMP) data. For CMP stacking the coverage is consistent with the number of traces sharing a common reflection point on flat subsurface reflectors. This relationship is not true for dipping reflectors. The deficiencies of CMP stacking with respect to imaging dipping events have long been overcome by the introduction of the dip-moveout (DMO) correction. However, the concept of coverage has not yet satisfactorily been updated to a 'DMO coverage' consistent with DMO stacking. A definition of constant-velocity DMO coverage will be proposed here. A subsurface reflector will be illuminated from a given source and receiver location if the time difference between the reflector zero-offset traveltime and the NMO- and DMO-corrected traveltime of the reflection event is less than half a dominant wavelength. Due to the fact that a subsurface reflector location is determined by its zero-offset traveltime, its strike and its dip, the DMO coverage also depends on these three parameters. For every surface location, the proposed DMO coverage consists of a 3D fold distribution over reflector strike, dip and zero-offset traveltime.     

On The Determination Of The Earth's Model – The Mean Equipotential Surface

The sea surface cannot be used as reference for Major Vertical Datum definition because its deviations from the ideal equipotential surface are very large compared to rms in the observed quantities. The quasigeoid is not quite suitable as the surface representing the most accurate Earth's model without some additional conditions, because it depends on the reference field. The normal Earth's model represented by the rotational level ellipsoid can be defined by the geocentric gravitational constant, the difference in the principal Earth's inertia moments, by the angular velocity of the Earth's rotation and by the semimajor axis or by the potential (U ₀ ) on the surface of the level ellipsoid. After determining the geopotential at the gauge stations defining Vertical Datums, gravity anomalies and heights should be transformed into the unique vertical system (Major Vertical Datum). This makes it possible to apply Brovar's (1995) idea of determining the reference ellipsoid by minimizing the integral, introduced by Riemann as the Dirichlet principle, to reach a minimum rms anomalous gravity field. Since the semimajor axis depends on tidal effects, potential U ₀ should be adopted as the fourth primary fundamental geodetic constant. The equipotential surface, the actual geopotential of which is equal to U ₀ , can be adopted as reference for realizing the Major Vertical Datum.     

Stochastic Hydrogeology: What Professionals Really Need?

Quantitative hydrogeology celebrated its 150th anniversary in 2006. Geostatistics is younger but has had a very large impact in hydrogeology. Today, geostatistics is used routinely to interpolate deterministically most of the parameters that are required to analyze a problem or make a quantitative analysis. In a small number of cases, geostatistics is combined with deterministic approaches to forecast uncertainty. At a more academic level, geostatistics is used extensively to study physical processes in heterogeneous aquifers. Yet, there is an important gap between the academic use and the routine applications of geostatistics. The reasons for this gap are diverse. These include aspects related to the hydrogeology consulting market, technical reasons such as the lack of widely available software, but also a number of misconceptions. A change in this situation requires acting at different levels. First, regulators must be convinced of the benefit of using geostatistics. Second, the economic potential of the approach must be emphasized to customers. Third, the relevance of the theories needs to be increased. Last, but not least, software, data sets, and computing infrastructure such as grid computing need to be widely available.