Introducing the Volcanic Unrest Index (VUI): a tool to quantify and communicate the intensity of volcanic unrest     

Sally H. Potter  Bradley J Scott  Gill E Jolly  Vince E Neall  David M Johnston 《Bulletin of Volcanology》2015,77(9):77

Accurately observing and interpreting volcanic unrest phenomena contributes towards better forecasting of volcanic eruptions, thus potentially saving lives. Volcanic unrest is recorded by volcano observatories and may include seismic, geodetic, degassing and/or geothermal phenomena. The multivariate datasets are often complex and can contain a large amount of data in a variety of formats. Low levels of unrest are frequently recorded, causing the distinction between background activity and unrest to be blurred, despite the widespread usage of these terms in unrest literature (including probabilistic eruption-forecasting models) and in Volcanic Alert Level (VAL) systems. Frequencies and intensities of unrest episodes are not easily comparable over time or between volcanoes. Complex unrest information is difficult to communicate simply to civil defence personnel and other non-scientists. The Volcanic Unrest Index (VUI) is presented here to address these issues. The purpose of the VUI is to provide a semi-quantitative rating of unrest intensity relative to each volcano’s past level of unrest and to that of analogous volcanoes. The VUI is calculated using a worksheet of observed phenomena. Ranges for each phenomenon within the worksheet can be customised for individual volcanoes, as demonstrated in the companion paper for Taupo Volcanic Centre, New Zealand (Potter et al. 2015). The VUI can be determined retrospectively for historical episodes of unrest based on qualitative observations, as well as for recent episodes with state-of-the-art monitoring. This enables a long time series of unrest occurrence and intensity to be constructed and easily communicated to end users. The VUI can also assist with VAL decision-making. We present and discuss two approaches to the concept of unrest.  相似文献   

The pitfalls of astrobiogeography     

Malte C. Ebach  Anthony C. Gill  David M. Williams 《Astrophysics and Space Science》2008,317(3-4):143-144

Biogeography, the study of organismal distribution, adheres to the same basic reasoning no matter where organisms are distributed. Wickramasinghe and Wickramasinghe (Astrophys. Space Sci. doi:10.1007/s10509-008-9851-2), however, are possibly the first to propose a mechanism of distribution for extraterrestrial organisms, thus venturing into the uncharted realm of astrobiogeography. The same logic used in the study of distributions on Earth applies to those of extraterrestrial microbes. Herein we attempt to introduce some pitfalls common in biogeography for those venturing into the new study of astrobiogeography.  相似文献   

Evaluating suitability of a tephra dispersal model as part of a risk assessment framework     

Gordon N. Keating  Jon D. Pelletier  Greg A. Valentine  William Statham 《Journal of Volcanology and Geothermal Research》2008

In volcanic risk assessment it is necessary to determine the appropriate level of sophistication for a given predictive model within the contexts of multiple sources of uncertainty and coupling between models. A component of volcanic risk assessment for the proposed radioactive waste repository at Yucca Mountain (Nevada, USA) involves prediction of dispersal of contaminated tephra during violent Strombolian eruptions and the subsequent transport of that tephra toward a hypothetical individual via surface processes. We test the suitability of a simplified model for volcanic plume transport and fallout tephra deposition (ASHPLUME) coupled to a surface sediment-transport model (FAR) that calculates the redistribution of tephra, and in light of inherent uncertainties in the system. The study focuses on two simplifying assumptions in the ASHPLUME model: 1) constant eruptive column height and 2) constant wind speed and direction during an eruption. Variations in tephra dispersal resulting from unsteady column height and wind conditions produced variations up to a factor of two in the concentration of tephra in sediment transported to the control population. However, the effects of watershed geometry and terrain, which control local remobilization of tephra, overprint sensitivities to eruption parameters. Because the combination of models used here shows limited sensitivity to the actual details of ash fall, a simple fall model suffices to estimate tephra mass delivered to the hypothetical individual.  相似文献   

Shallow plumbing systems for small-volume basaltic volcanoes   总被引：3，自引：3，他引：0  

Gordon N. Keating  Greg A. Valentine  Donathon J. Krier  Frank V. Perry 《Bulletin of Volcanology》2008,70(5):563-582

Eruptive dynamics in basaltic volcanoes are controlled, in part, by the conduit geometry. However, uncertainties in conduit shape and dike-to-conduit transition geometry have limited our predictive capability for hazards assessments. We characterize the subvolcanic geometry of small-volume basaltic volcanoes (magmatic volatile-driven eruptions, 0.1 to 0.5 km³) based on a synthesis of field studies of five basaltic volcanoes exposed to varying degrees by erosion and exhibiting feeder dikes, conduits, and vent areas ≤250 m depth. Study areas include East Grants Ridge (New Mexico, USA), Basalt Ridge, East Basalt Ridge, Paiute Ridge, and Southeast Crater Flat (Nevada, USA). Basaltic feeder dikes 250 to 100 m deep have typical widths of 4–12 m, with smooth host-rock contacts (rhyolite tuff). At depths less than 100 m, heterogeneities in the host rock form preferential pathways for small dike splays and sills, resulting in a 30-m effective width at 50 m depth. The development of a complex conduit at depths less than 70 m is reflected in bifurcating dikes and brecciation and incorporation of the country rock. The overall zone of effect at depths less than 50 m is ≤110 m wide (220 m elongated along the feeder dike). Based on comparisons with theoretical conduit flow models, the width of the feeder dike at depths from 250 to 500 m is expected to range from 1 to 10 m and is expected to decrease to about 1–2 m at depths greater than 500 m. The flaring shape of the observed feeder systems is similar to results of theoretical modeling using lithostatic pressure-balanced flow conditions. Sizes of observed conduits differ from modeled dimensions by up to a factor of 10 in the shallow subsurface (<50 m depth), but at depths greater than 100 m the difference is a factor of 2 to 4. This difference is primarily due to the fact that observed eroded conduits record the superimposed effects of multiple eruptive events, while theoretical model results define dimensions necessary for a single, steady eruption phase. The complex details of magma-host rock interactions observed at the study areas (contact welding, brecciation, bifurcating dikes and sills, and stoping) represent the mechanisms by which the lithostatic pressure-balanced geometry is attained. The similarity in the normalized shapes of theoretical and observed conduits demonstrates the appropriateness of the pressure-balanced modeling approach, consistent with the conclusions of Wilson and Head (J Geophys Res 86:2971–3001, 1981) for this type of volcano.  相似文献   

Reef margin collapse, gully formation and filling within the Permian Capitan Reef: Carlsbad Caverns, New Mexico, USA     

Gill M. Harwood  & Alan C. Kendall 《Sedimentology》1999,46(3):443-461

An area of reef margin collapse, gully formation and gully fill sedimentation has been identified and mapped within Left Hand Tunnel, Carlsbad Caverns. It demonstrates that the Capitan Reef did not, at all times, form an unbroken border to the Delaware Basin. Geopetally arranged sediments within cavities from sponge–algal framestones of the reef show that the in situ reef today has a 10° basinwards structural dip. Similar dips in adjacent back-reef sediments, previously considered depositional, probably also have a structural origin. Reoriented geopetal structures have also allowed the identification of a 200-m-wide, 25-m-deep gully within the reef, which has been filled by large (some  >15 m), randomly orientated and, in places, overturned blocks and boulders, surrounded by finer reef rubble, breccias and grainstones. Block supply continued throughout gully filling, implying that spalling of reef blocks was a longer term process and was not a by-product of the formation of the gully. Gully initiation was probably the result of a reef front collapse, with a continued instability of the gully bordering reef facies demonstrated by their incipient brecciation and by faults containing synsedimentary fills. Gully filling probably occurred during reef growth, and younger reef has prograded over the gully fill. Blocks contain truncated former aragonite botryoidal cements, indicating early aragonite growth within the in situ reef. In contrast, former high-magnesian calcite rind cements post-date sedimentation within the gully. The morphology of cavern passages is controlled by reef facies variation, with narrower passages cut into the in situ reef and wider passages within the gully fill. Gully fills may also constitute more permeable zones in the subsurface.  相似文献   

Application of microcosm experiments for quantifying lateral flow and evapotranspiration on recovering bog ecotypes     

Michael M. Swenson  Shane Regan  Laurence W. Gill 《水文研究》2020,34(22):4211-4225

The importance of characterizing the ecohydrological interactions in natural, damaged/drained, and restored bogs is underscored by the importance of peatlands to global climate change and the growing need for peatland restoration. An understudied aspect of peatland ecohydrology is how shallow lateral flow impacts local hydrological conditions and water balance, which are critical for peatland restoration success. A novel method is presented using microcosms installed in the field to understand the dynamics of shallow lateral flow. Analysis of the difference in water table fluctuation inside and outside the microcosm experimental areas allowed the water balance to be constrained and the calculation of lateral flow and evapotranspiration. As an initial demonstration of this method, a series of four microcosm experiments were set up in locations with differing ecological quality and land management histories, on a raised bog complex in the midlands of Ireland. The timing and magnitude of the lateral flow differed considerably between locations with differing ecological conditions, indicating that shallow lateral flow is an important determining factor in the ecohydrological trajectory of a recovering bog system. For locations where Sphagnum spp. moss layer was present, a slow continuous net lateral input of water from the upstream catchment area supported the water table during drought periods, which was not observed in locations lacking Sphagnum. Consistent with other studies, evapotranspiration was greater in locations with a Spaghnum moss layer than in locations with a surface of peat soil.  相似文献   

Book reviews     

Peter Valentine  J. M. B. Smith  P. Mitchell  Kevin J. Frawley  Marjorie Sullivan  A. J. Pitman 《The Australian geographer》1992,23(1):81-98

AN AUSTRALIAN DICTIONARY OF ENVIRONMENT AND PLANNING by A. Gilpin. 16 × 24 cm, xvi and 271 pages. Oxford University Press: Melbourne 1990 (ISBN 0 19 554806 X) $A60.00 (hard).

CONTINENT IN CRISIS: A Natural History of Australia by D. Smith, 13 × 20 cm, xii and 201 pages. Penguin: Melbourne 1990 (ISBN 0 14 011169 7) $A14.99 (soft).

THE END OF NATURE by B. McKibben. 14 × 22 cm, xi and 212 pages. Viking: London 1990 (ISBN 0 670 82877 7) $A29.99 (hard); distributed by Penguin Books.

THE FATE OF THE FOREST: Developers, Destroyers and Defenders of the Amazon by S. Hecht and A. Cockburn. 13 × 20 cm, xiii and 349 pages. Penguin: London (ISBN 0 14 013382 8) $A16.99 (soft).

ENVIRONMENT, AID AND REGIONALISM IN THE SOUTH PACIFIC (Pacific Research Monograph No. 22) by J. Carew‐Reid. 17 × 25 cm, xii and 185 pages. National Centre for Development Studies, Australian National University: Canberra 1989 (ISBN 0 7315 0673 1) $A25.00 (soft).

NEW SEEDS AND POOR PEOPLE by M. Lipton with R. Longhurst. 14 × 21 cm, xiv and 473 pages, Unwin Hyman: London 1989 (ISBN 0 04 45326 4) $A39.95 (soft).

CLIMATE CHANGE AND WORLD AGRICULTURE by M. Parry. 15 × 23 cm, xv and 157 pages. Earthscan: London 1990 (ISBN 1 85383 065 8) £9.95 (soft).

INTRODUCTION TO WORLD VEGETATION (Second Edition) by A. S. Collinson. 14 × 21 cm, x and 325 pages. Unwin Hyman: London 1988 (ISBN 0 04 581 030 3) $A95.00 (hard); (ISBN 0 04 581 031 1) $A39.95 (soft).

OCEANS OF LIFE OFF SOUTHERN AFRICA edited by A. I. L. Payne and R. J. M. Crawford. 22 × 29 cm, xii and 380 pages. Vlaeberg: Cape Town 1989 (ISBN 0 947461 01 9) $US30.00 plus $US5.00 postage (hard).

KARST GEOMORPHOLOGY AND HYDROLOGY by D. Ford and P. Williams. 15 × 23 cm, xv and 601 pages. Unwin Hyman: London 1989 (ISBN 0 04 551106 3) $A79.95 (soft).

ENVISIONING INFORMATION by E. R. TUFTE. 22 × 78 cm, 126 pages. Graphics Press: Cheshire, CT 1990 $US48.00 (hard). Available from Graphics Press, Box 430, Cheshire, Connecticut, 06410, USA.

A GUIDE TO REMOTE SENSING: Interpreting Images of the Earth by S. A. Drury. 22 × 27 cm, viii and 199 pages. Oxford University Press: Oxford 1991 (ISBN 0 19 854495 2) $A44.95 (soft).

THE CAINOZOIC IN AUSTRALIA: A Re‐appraisal of the Evidence (Special Publication No. 18) edited by M. A. J. William, P. De Deckker and A. P. Kershaw. 17 × 25 cm, x and 346 pages. Geological Society of Australia Inc: Sydney 1991 (ISBN 0 909869 76 6) $A60.00 (non‐members), $A40.00 (members) (soft).

MONSOONAL AUSTRALIA: Landscape, Ecology and Man in the Northern Lowlands edited by C. D. Haynes, M. G. Ridpath and M. A. J. Williams. 20 × 29 cm, xii and 231 pages. Balkema: Rotterdam 1991 (ISBN 90 6191 638 0) $A85.25 (hard).

SOILS: THEIR PROPERTIES AND MANAGEMENT: A Soil Conservation Handbook for New South Wales edited by P. E. V. Charman and B. W. Murphy. 21 × 27 cm, xix and 363 pages. Sydney University Press: Sydney 1991 (ISBN 0 424 00183 7) $A39.95 (soft).

VEGETATION (Atlas of Australian Resources, Third Series, Volume 6) by Australian Surveying and Land Information Group. 30 × 43 cm, 64 pages. Australian Surveying and Land Information Group: Canberra 1990 (ISBN 0 642 14993 3) $A39.95 (soft).

THE ATLAS OF NEPAL IN THE MODERN WORLD by M. Sill and J. Kirkby. 27 × 22 cm, 160 pages. Earthscan: London 1991 (ISBN 1 85383 032 1) £37.50 (hard).

DEVELOPMENT IN PRACTICE: Paved With Good Intentions by D. Porter, B. Allen and G. Thompson. 15 × 23 cm. Routledge: London 1990 (ISBN 0 415 16626 3) $A27.95 (soft); distributed by The Law Book Co.

CHINA'S SPATIAL ECONOMY: Recent Developments and Reforms edited by G. J. R. Linge and D. K. Forbes. 15 × 22 cm, xiii and 225 pages. Oxford University Press: Hong Kong 1991 (ISBN 0 19 585296 6) $A29.95 (hard).  相似文献   

Release and transformations of inorganic iodine by marine macroalgae     

Rosie Chance  Alex R. Baker  Frithjof C. Küpper  Claire Hughes  Bernard Kloareg  Gill Malin 《Estuarine, Coastal and Shelf Science》2009

A number of field and laboratory studies on the impact of marine macroalgae on dissolved inorganic iodine speciation are presented. Within tidally isolated rock pools, the brown macroalga Fucus serratus was found to both release stored iodide and to facilitate the reduction of iodate to iodide. In contrast, no discernible changes in iodine speciation were observed in rock pools containing green macroalgae of the genus Ulva. Incubation experiments confirmed that the macroalgae Laminaria digitata, F. serratus and Kallymenia antarctica release iodide, though the rate of release varied between species and between specimens of the same species. Application of oxidative stress by treatment with cell wall derived oligoguluronate elicitors increased the efflux of iodide by L. digitata approximately 20-fold. The release of iodide by macroalgae may impact upon the formation of volatile iodine species (molecular iodine and iodocarbons) that are of importance in the coastal atmosphere.  相似文献   

The vortex created by mass transfer between layers of a rotating fluid     

A. E. Gill  J. M. Smith  R. P. Cleaver  R. Hide  P. R. Jonas 《地球物理与天体物理流体动力学》2013,107(1):195-220

Abstract

A simple way to model stratification of the ocean or atmosphere is in terms of two superposed homogeneous layers of different density. Effects of cooling of the upper layer, such as that which occurs during bottom-water formation in the ocean, can be simulated by mass transfer from the upper layer to the lower layer. A model is constructed to see What effect such a mass transfer has on the flow when the mass transfer is confined to a limited region. The main effects are (i) doming of the interface, which maintains pressure gradients in balance with the velocity field, (ii) cyclonic rotation in the upper layer due to conservation of angular momentum of particles king drawn toward the sink, yet anticyclonic vorticity for those particles outside the mass transfer region due to shrinking of vortex lines drawn up over the dome. (iii) generally anticyclonic rotation in the lower layer due to particles tending to maintain their angular momentum while being pushed outwards, but some cyclonic rotation near the centre of mass transfer, due to momentum transfer from the upper layer. Similar effects to these are seen in the Greenland Sea where bottom water formation occurs. Results of the same sort are also found in a laboratory model of the process.  相似文献   

CAMAM: A Miniature Laser Ablation Ionisation Mass Spectrometer and Microscope‐Camera System for In Situ Investigation of the Composition and Morphology of Extraterrestrial Materials     

Marek Tulej  Andreas Riedo  Maike B. Neuland  Stefan Meyer  Peter Wurz  Nicolas Thomas  Valentine Grimaudo  Pavel Moreno‐García  Peter Broekmann  Anna Neubeck  Magnus Ivarsson 《Geostandards and Geoanalytical Research》2014,38(4):441-466

Performance studies of a microscope‐camera system (MCS) and a laser ablation/ionisation mass spectrometer (LIMS) instrument (referred to here as a laser mass spectrometer or LMS) are presented. These two instruments were designed independently for in situ analysis of solids on planetary surfaces and will be combined to a single miniature instrument suite for in situ chemical and morphological analysis of surface materials on planetary bodies. LMS can perform sensitive chemical (elemental, isotope and molecular) analyses with spatial resolution close to micrometre‐sized grains. It allows for studies with mass resolution (M/ΔM) up to 800 in ablation mode (elemental composition) and up to 1500 in desorption mode (molecular analysis). With an effective dynamic range of at least eight orders of magnitude, sensitive and quantitative measurements can be conducted of almost all elements and isotopes with a concentration larger than a few ppb atoms. Hence, in addition to the major element composition, which is important for the determination of mineralogical constituents of surface materials, trace elements can also be measured to provide information on mineral formation processes. Highly accurate isotope ratio measurements can be used to determine in situ geochronology of sample material and for investigations of various isotope fractionation processes. MCS can conduct optical imagery of mm‐sized objects at several wavelengths with micrometre spatial resolution for the characterisation of morphological surface details and to provide insight into surface mineralogy. Furthermore, MCS can help in the selection of sample surface areas for further mass spectrometric analysis of the chemical composition. Surface auto‐fluorescence measurements and images in polarised light are additional capabilities of the MCS, to identify either fluorescing minerals or organic materials, if present on the analysed surface, for further investigation by LMS. The results obtained by investigations of NIST reference materials, amino acid films and a natural graphite sample embedded in silicate rock are presented to illustrate the performance of the instruments and their potential to deliver chemical information for mineral and organic phases in their geological context.  相似文献