DOCSLIB.ORG

Predicting Tephra Dispersion with a Mesoscale Atmospheric Model and a Particle Fall Model: Application to Cerro Negro Volcano

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Predicting Tephra Dispersion with a Mesoscale Atmospheric Model and a Particle Fall Model: Application to Cerro Negro Volcano VOLUME 46 JOURNAL OF APPLIED METEOROLOGY AND CLIMATOLOGY FEBRUARY 2007 Predicting Tephra Dispersion with a Mesoscale Atmospheric Model and a Particle Fall Model: Application to Cerro Negro Volcano MARC A. BYRNE Department of Geography, University of South Florida, Tampa, Florida ARLENE G. LAING National Center for Atmospheric Research,* Boulder, Colorado CHARLES CONNOR Department of Geology, University of South Florida, Tampa, Florida (Manuscript received 8 October 2005, in final form 9 May 2006) ABSTRACT Models of volcanic ash (tephra) fallout are increasingly used to assess volcanic hazards in advance of eruptions and in near–real time. These models often approximate the wind field using simplistic assump- tions of the atmosphere that do not account for four-dimensional variations in wind velocity. The fifth- generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5) is used to improve forecasts of tephra dispersion. MM5 is a 3D model that can predict circulations in areas with sparse meteorological observations and complex terrain, such as volcanic plateaus. MM5 is applied to the 1995 eruption of Cerro Negro, Nicaragua. Validation of MM5 is achieved by comparing the simulated winds with rawinsonde observations. Estimates of diffusivity and particle settling velocities are used in conjunction with MM5-generated wind fields to forecast the major axes of the tephra dispersion. The predicted axes of dispersion derived from the MM5 winds approximate very closely the observed bilobate tephra accumulation and tephra plumes observed in satellite images. MM5 winds provide far more accurate spatial and temporal forecasts than do the wind assumptions that had been used previously to assess Cerro Negro tephra hazard. 1. Introduction 1994; Scott et al. 1995; Newhall and Punongbayan 1996). Tephra often causes water contamination, and Tephra, commonly known as volcanic ash, is defined airborne tephra can cause adverse effects on respiration as airborne volcanic ejecta of any size (Tilling et al. and irritation of eyes and nose (Latter 1989; Baxter 1987). It is a frequent product of volcanic eruptions. 1990). Deadly mudslides known as lahars, made of Volcanoes create numerous natural hazards that pose a tephra and water, often pick up more debris as they risk to society, but wind-driven tephra threatens far travel, and can move over 10 m sϪ1 (Iverson 1997). larger areas than any other volcanic hazard. Tephra Tephra that reaches the stratosphere affects climate— deposited on roofs can easily cause building collapse for example, lower surface temperatures following the (Wolfe 1992). Tephra can severely damage airplanes, 1991 eruption of Mount Pinatubo (Robock 2002). automobiles, and electrical equipment (Casadevall Because tephra poses numerous hazards, volcanolo- gists have modeled its dispersion for just over two de- cades. Although tephra models have increased in com- * The National Center for Atmospheric Research is sponsored plexity over time, their meteorological component has by the National Science Foundation. been conventionally simple, often out of necessity. As demand grows for real-time prediction and scenario- Corresponding author address: Arlene Laing, NCAR/MMM, based hazard assessment of tephra deposition, im- P.O. Box 3000, Boulder, CO 80307. provements to the atmospheric component of tephra E-mail: [email protected] modeling are essential. There is an important need for DOI: 10.1175/JAM2448.1 © 2007 American Meteorological Society 121 Unauthenticated | Downloaded 10/06/21 12:57 PM UTC JAM2448 122 JOURNAL OF APPLIED METEOROLOGY AND CLIMATOLOGY VOLUME 46 FIG. 1. (a) The 1995 eruption of Cerro Negro viewed from the northwest (photograph by B. Hill). (b) Distribution of tephra-fall deposits for November–December 1995 Cerro Negro eruption, based on field measurements by M. Kesseler (University of Geneva). Isopachs are in centimeters. Dashed line indicates the uncertainty in the location of the 0.1-cm isopach. Ruled and stippled patterns show the lava and cone. Topographic contours (100 m) are derived from 93-m-resolution digital elevation data. Coordinates are in universal transverse Mercator (UTM) coordinates, zone 16, WGS-84 spheroid. Inset map shows locations of major Nicaraguan volcanoes (from Hill et al. 1998). volcanic eruption hazard mapping at many volcanoes generation Pennsylvania State University–National around the world under different wind regimes. Many Center for Atmospheric Research (NCAR) Mesoscale volcanoes are located in countries that do not have the Model (MM5) are applied to the eruption of Cerro resources required to undertake detailed hazard map- Negro (Fig. 1), Nicaragua, that occurred on 19 Novem- ping. Atmospheric models in combination with tephra ber–6 December 1995. dispersion models can provide very valuable informa- tion to satisfy this requirement. a. Tephra modeling This study incorporates winds from a high-resolution atmospheric model to predict the major axes of tephra To understand tephra plumes better, many volca- dispersion and deposition. Winds produced by the fifth- nologists have numerically simulated volcanic eruptions Unauthenticated | Downloaded 10/06/21 12:57 PM UTC FEBRUARY 2007 B Y R N E E T A L . 123 This assumption may be made for simplicity’s sake, or because wind data are not easily accessible and, in many cases, are incomplete. Wind data are extrapo- lated sometimes from a single observation from a weather station tens of kilometers away (Barberi et al. 1990; Macedonio et al. 1994; Hill et al. 1998). This is a serious problem because the simplistic wind assumption neglects a major impact on deposition location. Much of the research on tephra dispersion involving atmospheric models has focused on aviation interests. The Volcanic Ash Forecast and Transport and Disper- sion model (VAFTAD, Heffter and Stunder 1993); the Canadian Emergency Response Model (CANERM), a FIG. 2. A weak tephra plume advected by wind (from Bona- 3D Eulerian model (Simpson et al. 2002); and “PUFF” donna and Phillips 2003). Here X represents the distance that a w (Searcy et al. 1998) are designed for real-time tracking particle is transported by wind during particle fall and is propor- tional to the ratio between wind speed and particle terminal ve- of volcanic ash clouds. These three models are intended locity, Hb is the level of neutral buoyancy, and Ht is the top of the for tracking middle-to-upper-tropospheric airborne plume. In vertical fallout, a particle falling from the current base ash. They do not predict low-tropospheric dispersal. at a point A will reach the ground at a point B1; if a plume Atmospheric dispersion models applied to surface develops in a wind field, a particle is likely to reach the ground at tephra accumulation have not been as widely investi- a point B2 depending on the wind velocity and the particle termi- nal velocity. gated as those used for aviation. Suzuki (1983) was the first to model tephra transport and deposition numeri- cally. He used a diffusion–advection equation for hori- (Suzuki 1983; Carey and Sigurdsson 1982; Connor et al. zontal particle motion in a temporally and spatially uni- 2001; Bonadonna and Phillips 2003). Physical assump- form wind field. The Suzuki model has been adjusted to tions are made about the eruption, eruption column, represent increasingly intricate volcanic eruptions and tephra plume. Some eruption parameters are esti- (Glaze and Self 1991; Armienti et al. 1988; Connor et al. mated. For example, satellite-estimated heights of 2001; Bonadonna et al. 2002; Bonadonna and Phillips eruption plumes can be prone to error (Tupper et al. 2003) and modified for parallel computation in the 2004). Geologists often attempt to reconstruct eruption “TEPHRA” model (Bonadonna et al. 2005). Although dynamics from ancient deposits. This activity is essen- TEPHRA is sophisticated in its representation of vol- tial in volcanic hazard assessment. However, it is not canic eruptions, it uses a single wind velocity profile as always clear which aspects of the deposit reflect volca- its input and assumes uniformed winds over each x–y nological conditions, such as eruption column height, domain for each altitude. and which aspects of the deposit can be explained by In a study similar to ours, Turner and Hurst (2001) meteorological conditions. used atmospheric and dispersion models to forecast Modeling tephra movement in the atmosphere is cru- tephra deposition from Mount Ruapehu, New Zealand. cial for modeling tephra accumulation. Once tephra They compared “ASHFALL” (Hurst and Turner particles in the eruption column have achieved their 1999), a simplified Suzuki model, with a combination of maximum height, their movement depends upon their the Regional Atmospheric Modeling System (RAMS) characteristics (density, shape, terminal fall velocity) and the Hybrid Particle and Concentration Transport and, very important, wind. For most eruptions, tephra model (HYPACT). Although HYPACT had merit in plumes are advected by winds and become more diffuse tracking tephra plumes, it was not suitable for quanti- with time and distance downwind (Bursik 1998). In fying tephra deposition depth because of shortcomings general, ballistic ejecta reach the ground very quickly, related to the distribution of particle fall velocities. whereas the finest tephra settles last (Fig. 2). Vertical However, the RAMS–HYPACT suite produced more wind shear can create irregular deposition patterns. Al- accurate forecasts than did ASHFALL and demon- though
Load more

Recommended publications
  • A Detection of Milankovitch Frequencies in Global Volcanic Activity
    A detection of Milankovitch frequencies in global volcanic activity Steffen Kutterolf1*, Marion Jegen1, Jerry X. Mitrovica2, Tom Kwasnitschka1, Armin Freundt1, and Peter J. Huybers2 1Collaborative Research Center (SFB) 574, GEOMAR, Wischhofstrasse 1-3, 24148 Kiel, Germany 2Department of Earth & Planetary Sciences, Harvard University, Cambridge, Massachusetts 02138, USA ABSTRACT 490 k.y. in the Central American Volcanic Arc A rigorous detection of Milankovitch periodicities in volcanic output across the Pleistocene- (CAVA; Fig. 1). We augment these data with Holocene ice age has remained elusive. We report on a spectral analysis of a large number of 42 tephra layers extending over ~1 m.y. found well-preserved ash plume deposits recorded in marine sediments along the Pacifi c Ring of in Deep Sea Drilling Project (DSDP) and Fire. Our analysis yields a statistically signifi cant detection of a spectral peak at the obliquity Ocean Drilling Program (ODP) Legs offshore period. We propose that this variability in volcanic activity results from crustal stress changes of Central America. The marine tephra records associated with ice age mass redistribution. In particular, increased volcanism lags behind in Central America are dated using estimated the highest rate of increasing eustatic sea level (decreasing global ice volume) by 4.0 ± 3.6 k.y. sedimentation rates and/or through correlation and correlates with numerical predictions of stress changes at volcanically active sites. These with radiometrically dated on-land deposits results support the presence of a causal link between variations in ice age climate, continental (e.g., Kutterolf et al., 2008; also see the GSA stress fi eld, and volcanism.
    [Show full text]
  • Extending the Late Holocene White River Ash Distribution, Northwestern Canada STEPHEN D
    ARCTIC VOL. 54, NO. 2 (JUNE 2001) P. 157– 161 Extending the Late Holocene White River Ash Distribution, Northwestern Canada STEPHEN D. ROBINSON1 (Received 30 May 2000; accepted in revised form 25 September 2000) ABSTRACT. Peatlands are a particularly good medium for trapping and preserving tephra, as their surfaces are wet and well vegetated. The extent of tephra-depositing events can often be greatly expanded through the observation of ash in peatlands. This paper uses the presence of the White River tephra layer (1200 B.P.) in peatlands to extend the known distribution of this late Holocene tephra into the Mackenzie Valley, northwestern Canada. The ash has been noted almost to the western shore of Great Slave Lake, over 1300 km from the source in southeastern Alaska. This new distribution covers approximately 540000 km2 with a tephra volume of 27 km3. The short time span and constrained timing of volcanic ash deposition, combined with unique physical and chemical parameters, make tephra layers ideal for use as chronostratigraphic markers. Key words: chronostratigraphy, Mackenzie Valley, peatlands, White River ash RÉSUMÉ. Les tourbières constituent un milieu particulièrement approprié au piégeage et à la conservation de téphra, en raison de l’humidité et de l’abondance de végétation qui règnent en surface. L’observation des cendres contenues dans les tourbières permet souvent d’élargir notablement les limites spatiales connues des épisodes de dépôts de téphra. Cet article recourt à la présence de la couche de téphra de la rivière White (1200 BP) dans les tourbières pour agrandir la distribution connue de ce téphra datant de l’Holocène supérieur dans la vallée du Mackenzie, située dans le Nord-Ouest canadien.
    [Show full text]
  • Explosive Eruptions
    Explosive Eruptions -What are considered explosive eruptions? Fire Fountains, Splatter, Eruption Columns, Pyroclastic Flows. Tephra – Any fragment of volcanic rock emitted during an eruption. Ash/Dust (Small) – Small particles of volcanic glass. Lapilli/Cinders (Medium) – Medium sized rocks formed from solidified lava. – Basaltic Cinders (Reticulite(rare) + Scoria) – Volcanic Glass that solidified around gas bubbles. – Accretionary Lapilli – Balls of ash – Intermediate/Felsic Cinders (Pumice) – Low density solidified ‘froth’, floats on water. Blocks (large) – Pre-existing rock blown apart by eruption. Bombs (large) – Solidified in air, before hitting ground Fire Fountaining – Gas-rich lava splatters, and then flows down slope. – Produces Cinder Cones + Splatter Cones – Cinder Cone – Often composed of scoria, and horseshoe shaped. – Splatter Cone – Lava less gassy, shape reflects that formed by splatter. Hydrovolcanic – Erupting underwater (Ocean or Ground) near the surface, causes violent eruption. Marr – Depression caused by steam eruption with little magma material. Tuff Ring – Type of Marr with tephra around depression. Intermediate Magmas/Lavas Stratovolcanoes/Composite Cone – 1-3 eruption types (A single eruption may include any or all 3) 1. Eruption Column – Ash cloud rises into the atmosphere. 2. Pyroclastic Flows Direct Blast + Landsides Ash Cloud – Once it reaches neutral buoyancy level, characteristic ‘umbrella cap’ forms, & debris fall. Larger ash is deposited closer to the volcano, fine particles are carried further. Pyroclastic Flow – Mixture of hot gas and ash to dense to rise (moves very quickly). – Dense flows restricted to valley bottoms, less dense flows may rise over ridges. Steam Eruptions – Small (relative) steam eruptions may occur up to a year before major eruption event. .
    [Show full text]
  • Canadian Volcanoes, Based on Recent Seismic Activity; There Are Over 200 Geological Young Volcanic Centres
    Volcanoes of Canada 1 V4 C.J. Hickson and M. Ulmi, Jan. 3, 2006 • Global Volcanism and Plate tectonics Where do volcanoes occur? Driving forces • Volcano chemistry and eruption types • Volcanic Hazards Pyroclastic flows and surges Lava flows Ash fall (tephra) Lahars/Debris Flows Debris Avalanches Volcanic Gases • Anatomy of an Eruption – Mt. St. Helens • Volcanoes of Canada Stikine volcanic belt Presentation Outline Anahim volcanic belt Wells Gray – Clearwater volcanic field 2 Garibaldi volcanic belt • USA volcanoes – Cascade Magmatic Arc V4 Volcanoes in Our Backyard Global Volcanism and Plate tectonics In Canada, British Columbia and Yukon are the host to a vast wealth of volcanic 3 landforms. V4 How many active volcanoes are there on Earth? • Erupting now about 20 • Each year 50-70 • Each decade about 160 • Historical eruptions about 550 Global Volcanism and Plate tectonics • Holocene eruptions (last 10,000 years) about 1500 Although none of Canada’s volcanoes are erupting now, they have been active as recently as a couple of 4 hundred years ago. V4 The Earth’s Beginning Global Volcanism and Plate tectonics 5 V4 The Earth’s Beginning These global forces have created, mountain Global Volcanism and Plate tectonics ranges, continents and oceans. 6 V4 continental crust ic ocean crust mantle Where do volcanoes occur? Global Volcanism and Plate tectonics 7 V4 Driving Forces: Moving Plates Global Volcanism and Plate tectonics 8 V4 Driving Forces: Subduction Global Volcanism and Plate tectonics 9 V4 Driving Forces: Hot Spots Global Volcanism and Plate tectonics 10 V4 Driving Forces: Rifting Global Volcanism and Plate tectonics Ocean plates moving apart create new crust.
    [Show full text]
  • Largest Explosive Eruption in Historical Times in the Andes at A.D
    b- Largest explosive eruption in historical times in the Andes at A.D. Huaynaputina volcano, 1600, southern Peru Jean-Claude ThOuret* IRD and Instituto Geofisicodel PerÚ, Calle Calatrava 21 6. Urbanización Camino Real, La Molina, Lima 12, Perú Jasmine Davila Instituto Geofísico del Perú, Lima, Perú Jean-Philippe Eissen IRD Centre de Brest BP 70, 29280 Plouzane Cedex, France ABSTRACT lent [DREI volume. km': Table The The largest esplosive eruption (volcanic explosivity index of 6) in historical times in the 4.4-5.6 I). tephra is composed of -SO% pumice with rhyolitic Andes took place in 1600 at Huaynaputina volcano in southern Peru. According to chroni- A.D. glass, crystals (mostly amphibole and bio- cles, the eruption began on February 19 with a Plinian phase and lasted until March 6. Repeated 15% tite), and 5% xenoliths including hydrothermally tephra falls, pyroclastic flows, and surges devastated an area 70 x 40 kni? west of the vent and altered fragments from the volcanic and sedimen- affected all of southern Peru, and earthquakes shook the city of Arequipa 75 km away. Eight tnry bedrock, and a small amount of accessory lwa deposits, totaling 10.2-13.1 km3 in bulk volume, are attributed to this eruption: (1) a widespread, fragments. The erupted pumice is a white, , -S.1 kn3 pumice-fall deposit; (2) channeled ignimbrites (1.6-2 km3) with (3) ground-surge and medium-potassicdacite (average SiO, and ash-cloud-surge deposits; (4) widespread co-ignimbrite ash layers; (5) base-surge deposits; (6) 63.6% 1.85% hlgO) of the potassic calc-alkalic suite.
    [Show full text]
  • Remotely Assessing Tephra Fall Building Damage and Vulnerability: Kelud Volcano, Indonesia George T
    Williams et al. Journal of Applied Volcanology (2020) 9:10 https://doi.org/10.1186/s13617-020-00100-5 RESEARCH Open Access Remotely assessing tephra fall building damage and vulnerability: Kelud Volcano, Indonesia George T. Williams1,2* , Susanna F. Jenkins1,2, Sébastien Biass1, Haryo Edi Wibowo3,4 and Agung Harijoko3,4 Abstract Tephra from large explosive eruptions can cause damage to buildings over wide geographical areas, creating a variety of issues for post-eruption recovery. This means that evaluating the extent and nature of likely building damage from future eruptions is an important aspect of volcanic risk assessment. However, our ability to make accurate assessments is currently limited by poor characterisation of how buildings perform under varying tephra loads. This study presents a method to remotely assess building damage to increase the quantity of data available for developing new tephra fall building vulnerability models. Given the large number of damaged buildings and the high potential for loss in future eruptions, we use the Kelud 2014 eruption as a case study. A total of 1154 buildings affected by falls 1–10 cm thick were assessed, with 790 showing signs that they sustained damage in the time between pre- and post-eruption satellite image acquisitions. Only 27 of the buildings surveyed appear to have experienced severe roof or building collapse. Damage was more commonly characterised by collapse of roof overhangs and verandas or damage that required roof cladding replacement. To estimate tephra loads received by each building we used Tephra2 inversion and interpolation of hand-contoured isopachs on the same set of deposit measurements.
    [Show full text]
  • Potential Impacts from Tephra Fall to Electric Power Systems: a Review and Mitigation Strategies
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by UC Research Repository Bull Volcanol DOI 10.1007/s00445-012-0664-3 REVIEW ARTICLE Potential impacts from tephra fall to electric power systems: a review and mitigation strategies J. B. Wardman & T. M. Wilson & P. S. Bodger & J. W. Cole & C. Stewart Received: 9 May 2012 /Accepted: 20 September 2012 # Springer-Verlag Berlin Heidelberg 2012 Abstract Modern society is highly dependent on a reliable identified to avoid future unplanned interruptions. To ad- electricity supply. During explosive volcanic eruptions, dress this need, we have produced a fragility function that tephra contamination of power networks (systems) can com- quantifies the likelihood of insulator flashover at different promise the reliability of supply. Outages can have signifi- thicknesses of tephra. Finally, based on our review of case cant cascading impacts for other critical infrastructure studies, potential mitigation strategies are summarised. sectors and for society as a whole. This paper summarises Specifically, avoiding tephra-induced insulator flashover known impacts to power systems following tephra falls by cleaning key facilities such as generation sites and trans- since 1980. The main impacts are (1) supply outages from mission and distribution substations is of critical importance insulator flashover caused by tephra contamination, (2) dis- in maintaining the integrity of an electric power system. ruption of generation facilities, (3) controlled outages during tephra cleaning, (4) abrasion and corrosion of exposed Keywords Volcanic ash . Eruption . Electricity . equipment and (5) line (conductor) breakage due to tephra Generation . Transmission . Distribution . Substation loading. Of these impacts, insulator flashover is the most common disruption.
    [Show full text]
  • Volcanoes: the Ring of Fire in the Pacific Northwest
    Volcanoes: The Ring of Fire in the Pacific Northwest Timeframe Description 1 fifty minute class period In this lesson, students will learn about the geological processes Target Audience that create volcanoes, about specific volcanoes within the Ring of Fire (including classification, types of volcanoes, formation process, Grades 4th- 8th history and characteristics), and about how volcanoes are studied and why. For instance, students will learn about the most active Suggested Materials submarine volcano located 300 miles off the coast of Oregon — Axial • Volcanoe profile cards Seamount. This submarine volcano is home to the first underwater research station called the Cabled Axial Seamount Array, from which researchers stream data and track underwater eruptions via fiber optic cables. Students will learn that researchers also monitor Axial Seamount using research vessels and remote operated vehicles. Objectives Students will: • Synthesize and communicate scientific information about specific volcanoes to fellow students • Will learn about geological processes that form volcanoes on land and underwater • Will explore the different methods researchers employ to study volcanoes and related geological activity Essential Questions What are the different processes that create volcanoes and how/why do researchers study volcanic activity? How, if at all, do submarine volcanoes differ from volcanoes on land? Background Information A volcano occurs at a point where material from the inside of the Earth is escaping to the surface. Volcanoes Contact: usually occur along the fault lines that SMILE Program separate the tectonic plates that make [email protected] up the Earth's crust (the outermost http://smile.oregonstate.edu/ layer of the Earth). Typically (though not always), volcanoes occur at one of two types of fault lines.
    [Show full text]
  • Indirect Tephra Volume Estimations Using Theorical Models for Some Chilean Historical Volcanic Eruptions with Sustained Columns J.E
    Indirect tephra volume estimations using theorical models for some Chilean historical volcanic eruptions with sustained columns J.E. Romero*1,2 , J.G. Viramonte 3 & R. A. Scasso 4 (1) Universidad de Atacama, Departamento de Geología. Copayapu 485, Copiapó. (2) Proyecto Archivo Nacional de Volcanes, www.archivonacionaldevolcanes.cl (3) INENCO – GEONORTE Universidad Nacional de Salta-CONICET, Av. Bolivia 5150–4400, Salta , Argentina (4)IGeBA-CONICET, Universidad de Buenos Aires, Departamento de Ciencias Geológicas, Int. Guiraldes 2160, C1428EHA, Ciudad Universitaria, Pab. II, Buenos Aires, Argentina. * Presenting Author’s email: [email protected] Introduction During explosive volcanic eruptions, diverse pyroclastic products are discharged from an eruptive column. Those columns are divided into three zones; 1) a basal gas thrust one, 2) medial convective and 3) a top umbrella region (Sparks, 1986) as is indicated in figure 1a. In this last one, where the column is dispersed laterally and radially forming a dispersion cloud or volcanic plume, the column reaches an Ht region due its momentum (Fig.1a). There has been defined two types of eruptive columns in relation with the time between single explosions. If the time between explosions exceeds the time of ascension of a column until its Ht height, the column is thermal, and in the opposite case, if the ascension time is smaller than the separation between explosions, this column is sustained (Sparks, 1986; Carey and Bursik, 2000). A good agreement has been found in the prediction of column heights and field observations for the case of columns which extends higher than the tropopause (Settle, 1978; Wilson et al, 1978; Sparks and Wilson, 1982; Sparks, 1986).
    [Show full text]
  • Preservation of Thin Tephra Russell Blong1* , Neal Enright2 and Paul Grasso3
    Blong et al. Journal of Applied Volcanology (2017) 6:10 DOI 10.1186/s13617-017-0059-4 RESEARCH Open Access Preservation of thin tephra Russell Blong1* , Neal Enright2 and Paul Grasso3 Abstract The preservation of thin (<300 mm thick) tephra falls was investigated at four sites in Papua New Guinea (PNG), Alaska and Washington, USA. Measurements of the variations in the thickness of: (i) Tibito Tephra 150 km downwind from the source, Long Island (PNG) erupted mid-seventeenth century; (ii) St Helens W tephra (erupted 1479–80 A.D.) on the slopes of the adjacent Mt. Rainier in Washington State; (iii) Novarupta (1912) tephra preserved on Kodiak Island (Alaska, USA); and (iv) an experimentally placed tephra at a site near Mt. Hagen (PNG) allow tentative conclusions to be drawn about the relative importance to tephra preservation of slope gradients, vegetation cover and soil faunal activity. Results for the experimental tephra suggest that compaction occurs rapidly post-deposition and that estimates of tephra thickness and bulk density need to indicate how long after deposition thickness measurements were made. These studies show that erosional reworking of thin tephra is not rapid even on steeper slopes in high rainfall environments. In Papua New Guinea a 350-year old tephra is rarely present under forest but is well-preserved under alpine grasslands. On Mt. Rainier 500-year old tephra is readily preserved under forest but absent under grasslands as a result of gopher activity. Despite the poor relationship between tephra thickness and slope steepness the thickness of thin tephras is highly variable. On Kodiak Island thickness variability across a few metres is similar to that observed across the whole northeast of the island.
    [Show full text]
  • Significance of a Near-Source Tephra-Stratigraphic Sequence to the Eruptive History of Hayes Volcano, South- Central Alaska
    Significance of a Near-Source Tephra-Stratigraphic Sequence to the Eruptive History of Hayes Volcano, South- Central Alaska Scientific Investigations Report 2014–5133 U.S. Department of the Interior U.S. Geological Survey FRONT COVER Portion of the Hayes River outcrop 31 km northeast of Hayes Volcano, along the Hayes River immediately downstream from the terminus of Hayes Glacier. Photograph by Andrew Calvert, 2011. Significance of a Near-Source Tephra- Stratigraphic Sequence to the Eruptive History of Hayes Volcano, South-Central Alaska By Kristi L. Wallace, Michelle L. Coombs, Leslie A. Hayden, and Christopher F. Waythomas Scientific Investigations Report 2014–5133 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior SALLY JEWELL, Secretary U.S. Geological Survey Suzette M. Kimball, Acting Director U.S. Geological Survey, Reston, Virginia: 2014 For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment—visit http://www.usgs.gov or call 1–888–ASK–USGS For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/ pubprod To order this and other USGS information products, visit http://store.usgs.gov Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this information product, for the most part, is in the public domain, it also may containcopyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.
    [Show full text]
  • Volcanic Impacts on Grasslands – a Review
    Volcanic impacts on grasslands – a review Arnalds Ó. Agricultural University of Iceland Corresponding author: [email protected] Abstract Volcanic eruptions have a wide range of effects on many of the Earth’s grassland systems, such as in Africa, the Americas and Iceland. The effects are determined by the severity of the impact, vegetation height and the resilience of the impacted system. Biological soil crusts, often an important component of dryland grazing systems, are severely affected by thin deposition of volcanic ash, whereas taller vegetation with ample nutrient supplies is more tolerant to such disturbances. Redistribution of airborne unconsolidated volcanic materials (tephra, including volcanic ash) in the aftermath of eruptions is often quite harmful to ecosystem survival. The interaction between volcanic events and land-use practices such as grazing is detrimental. Alien plant species in volcanic areas can severely interfere with ecosystem recovery. Keywords: tephra, volcanic ash, volcanic impact, grazing Introduction There are 1545 active volcanoes with >9000 eruptions listed in the current Smithsonian Catalog of Active Volcanoes (Siebert et al., 2010). About 70 volcanoes are active each year on average, but most eruptions are small. The majority of volcanoes occur at the margins of tectonic plates, which account for 94% of the volcanic activity, with the ‘Pacific Ring of Fire’ and the African Rift Valley being good examples (Simkin and Siebert, 2000). The activity occurs also in relation to so-called hot spots, which are isolated and transfer heat from the mantle (Bjarnason, 2008), such as on the islands of Hawaii, Galapagos and Iceland, and in Yellowstone, which is an example of intra-continental volcanic hot-spot activity.
    [Show full text]