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Centre Atm. Sci., University of Cambridge, UK
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- PublicationOpen AccessErratum to ‘A multidisciplinary effort to assign realistic source parameters to models of volcanic ash-cloud transport and dispersion during eruptions’ by Mastin et al. [J. Volcanol. Geotherm. Res. 188(2009)1–21](2010-04-01)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;Mastin, L. G.; U.S. Geological Survey, Cascades Volcano Observatory, Vancouver, USA ;Guffanti, M.; U.S. Geological Survey Reston, Virginia, USA ;Servranckx, R.; Canadian Meteorological Centre, Québec, Canada ;Webley, P.; Geophysical Institute, University of Alaska Fairbanks, USA ;Barsotti, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Dean, K.; Geophysical Institute, University of Alaska Fairbanks, USA ;Durant, A.; Department of Earth Sciences, University of Bristol, England ;Ewert, J. W.; U.S. Geological Survey, Cascades Volcano Observatory, Vancouver, USA ;Neri, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Rose, W. I.; Department of Geological and Engineering Sciences, Michigan Technological University, USA ;Schneider, D.; USGS Alaska Volcano Observatory, Anchorage, AK, USA ;Siebert, L.; Smithsonian Institution, Washington, D.C., USA ;Stunder, B.; Air Resources Laboratory, National Oceanic and Atmospheric Administration, Silver Spring, MD, USA ;Swanson, G.; National Oceanic and Atmospheric Administration, Camp Springs, MD, USA ;Tupper, A.; Bureau of Meteorology, Darwin, Casuarina, NT, Australia ;Volentik, A.; Department of Geology, University of South Florida, Tampa, FL, USA ;Waythomas, C. F.; USGS Alaska Volcano Observatory, Anchorage, AK, USA; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; no abstract165 107 - PublicationRestrictedUltra-distal tephra deposits from super-eruptions: Examples from Toba, Indonesia and Taupo Volcanic Zone, New Zealand(2012)
; ; ; ; ; ; ;Matthews, N. E.; Dept. Earth. Sci, University of Oxford, UK ;Smith, V. C.; Res. Lab. Archeology and Hist. of Art, University of Oxford, UK ;Costa, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Durant, A. J.; Centre Atm. Sci., University of Cambridge, UK ;Pyle, D. M.; Dept. Earth. Sci, University of Oxford, UK ;Pearce, N. J. G.; Inst. Geography and Earth. Sci., Aberystwyth University, UK; ;; ; ; Voluminous rhyolitic eruptions from Toba, Indonesia, and Taupo Volcanic Zone (TVZ), New Zealand have dispersed volcanic ash over vast areas in the late Quaternary. The w74 ka Youngest Toba Tuff (YTT) eruption deposited ash over the Bay of Bengal and the Indian subcontinent to the west. The w340 ka Whakamaru eruption (TVZ) deposited the widespread Rangitawa Tephra, dominantly to the southeast (in addition to occurrences northwest of vent), extending across the landmass of New Zealand, and the South Pacific Ocean and Tasman Sea with distal terrestrial exposures on the Chatham Islands. These super-eruptions involved w2500 km3 and w1500 km3 of magma (dense-rock equivalent; DRE), respectively. Ultra-distal terrestrial exposures of YTT at two localities in India, Middle Son Valley, Madhya Pradesh, and Jurreru River Valley, Andhra Pradesh, at distances of >2000 km from the source caldera, show a basal ‘primary’ ashfall unit w4 cm thick, although deposits containing reworked ash are up to w3 m in total thickness. Exposures of Rangitawa Tephra on the Chatham Islands, >900 km from the source caldera, are w15e30 cm thick. At more proximal localities (w200 km from source), Rangitawa Tephra is w55e70 cm thick and characterized by a crystal-rich basal layer and normal grading. Both distal tephra deposits are characterized by very-fine ash (with high PM10 fractions) and are crystal-poor. Glass chemistry, stratigraphy and grain-size data for these distal tephra deposits are presented with comparisons of their correlation, dispersal and preservation. Using field observations, ash transport and deposition were modeled for both eruptions using a semi-analytical model (HAZMAP), with assumptions concerning average wind direction and strength during eruption, column shape and vent size. Model outputs provide new insights into eruption dynamics and better estimates of eruption volumes associated with tephra fallout. Modeling based on observed YTT distal tephra thicknesses indicate a relatively low (<40 km high), very turbulent eruption column, consistent with deposition from a co-ignimbrite cloud extending over a broad region. Similarly, the Whakamaru eruption was modeled as producing a predominantly Plinian column (w45 km high), with dispersal to the southeast by strong prevailing winds. Significant ash fallout of the main dispersal direction, to the northwest of source, cannot be replicated in this modeling. The widespread dispersal of large volumes of fine ash from both eruptions may have had global environmental consequences, acutely affecting areas up to thousands of kilometers from vent.326 21 - PublicationRestrictedA model for wet aggregation of ash particles in volcanic plumes and clouds: 2. Model application(2010-09-01)
; ; ; ; ;Folch, A.; Barcelona Supercomputing Center, Barcelona, Spain ;Costa, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Durant, A.; Department of Geography, University of Cambridge, Cambridge, UK ;Macedonio, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; ; ; The occurrence of particle aggregation has a dramatic effect on the transport and sedimentation of volcanic ash. The aggregation process is complex and can occur under different conditions and in multiple regions of the plume and in the ash cloud. In the companion paper, Costa et al. develop an aggregation model based on a fractal relationship to describe the rate particles are incorporated into ash aggregates. The model includes the effects of both magmatic and atmospheric water present in the volcanic cloud and demonstrates that the rate of aggregation depends on the characteristics of the initial particle size distribution. The aggregation model includes two parameters, the fractal exponent Df, which describes the efficiency of the aggregation process, and the aggregate settling velocity correction factor ye, which influences the distance at which distal mass deposition maxima form. Both parameters are adjusted using features of the observed deposits. Here this aggregation model is implemented in the FALL3D volcanic ash transport model and applied to the 18 May 1980 Mount St. Helens and the 17–18 September 1992 Crater Peak eruptions. For both eruptions, the optimized values for Df (2.96–3.00) and ye (0.27–0.33) indicate that the ash aggregates had a bulk density of 700–800 kg m−3. The model provides a higher degree of agreement than previous fully empirical aggregation models and successfully reproduces the depositional characteristics of the deposits investigated over a large range of scales, including the position and thickness of the secondary maxima.303 23