DOCSLIB.ORG

Center of the Iceland Hotspot Experiences Volcanic Unrest

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Center of the Iceland Hotspot Experiences Volcanic Unrest Eos, Vol. 78, No. 35, September 2, 1997 the scientific community of this unusual seis­ Center of the Iceland Hotspot mic activity and the possibility of eruptive ac­ tivity. The seismic swarm continued throughout September 29 and 30, with in­ Experiences Volcanic Unrest creasing intensity. Hundreds of earthquakes PAGES 369, 374-375 were recorded each day, including more than 10 events larger than 3 in magnitude. The earthquakes were initially located below Pall Einarsson, Bryndis Brandsdottir, Magnus Tumi Gudmundsson, the northwestern rim of the Bardarbunga cal­ Helgi Bjornsson, Karl Gronvold and Freysteinn Sigmundsson dera (Figure 2) and then, over 24 hours, mi­ grated 20 km southward toward Grimsvotn. The earthquakes were accompanied by high- A volcanic eruption beneath the Vatna­ larly in Iceland, where almost one-fifth of the frequency (3 Hz) continuous tremor, which jokull ice cap in central Iceland (Figure 1) be­ population perished in the resulting famine, indicated that magma from a magma cham­ gan on September 30,1996, along a but also in Europe and North America. The ber in the Bardarbunga region was being in­ 7-km-long fissure between the volcanoes Bar- 1996 eruption offers a rare opportunity to jected to the south, feeding a dyke. darbunga and Grimsvotn. The eruption con­ study an eruption beneath an ice sheet, but Following a meeting of the Science Advi­ 3 tinued for 13 days and produced -0.5 km of such eruptions were common during the sory Board of the Civil Defense Council, a basaltic andesite. Meltwater from the erup­ Pleistocene; that is, prior to 11,000 years B.P. public warning of a possible eruption in tion site flowed into the caldera lake of the northwest Vatnajokull was issued on Septem­ Premonitory Activity and Warning Grimsvotn volcano, where it accumulated be­ ber 30. In the evening the earthquake activity neath a floating ice shelf. The lake's ice dam The eruption was preceded by an unusual near Grimsvotn decreased markedly, while was lifted off the glacier bed on November 4, activity at Bardarbunga continued. The seis­ 3 sequence of earthquakes, beginning on Sep­ and in the next two days more than 3 km of tember 29 at 1048 LT with a magnitude 5.4 mograph at Grimsvotn began recording con­ water drained out beneath the glacier and (Ms) event at the northern rim of the Bardar­ tinuous, low-amplitude eruption tremor. The flushed down to the south coast's alluvial bunga caldera. Many similar earthquakes sudden decrease of the earthquake activity plain, causing extensive flooding and dam­ have occurred beneath the Bardarbunga vol­ and the onset of the eruption tremor may be age to transportation and communication sys­ cano during the last 22 years, but none had taken as evidence that the predicted erup­ tems. significant aftershocks, nor were they fol­ tion had begun. The major eruption occurred in the most lowed by magmatic activity. This time the productive area of Iceland's hotspot. It was earthquake was followed by an intense earth­ The Eruption preceded by several years of unrest, includ­ quake swarm, including five events larger ing both earthquakes and small eruptions, than 3 in magnitude within two hours of the The tremor amplitude increased slowly which may signal the onset of a period of main quake. and reached a maximum on the morning of high volcanic activity in the area. The Ice­ Scientists at the University of Iceland noti­ October 1. The eruption site was discovered land hotspot is centered on Central Iceland, fied the Civil Defense authorities as well as early that morning by an observer in an air- where it overlaps with the Eastern Volcanic Zone (EVZ, Figure 1), which represents the mid-Atlantic plate boundary. The plates are separating at ~2 cm per year. Fig. 1. Tectonic This area is characterized by large volca­ map of Iceland show­ noes, Bardarbunga, Grimsvotn, Hamarinn, ing fissure swarms Kverkfjoll, and Tungnafellsjokull [Bjornsson along the plate and Einarsson, 1990], and a large part of it is boundaries and vol­ covered by the Vatnajokull ice cap (Figure canoes and calderas 1). Mapping of the subglacial topography by in the Eastern Vol­ radio echo sounding has revealed large cal- canic Zone (EVZ). deras in the Bardarbunga, Grimsvotn, and Letters mark the vol­ Kverkfjoll volcanoes [Bjornsson, 1988]. A canoes Krafla (K), hint of a yet larger circular structure can also Tungnafellsjokull be seen in the subglacial topography. It ex­ (T), Bardarbunga tends from the southern flank of Bardar­ (B), Kverkfjoll (Kv), bunga and encloses Grimsvotn. Hamarinn is Hamarinn (H), situated on its western rim (Figure 2). Grimsvotn (G), and the Skeidardrsandur The Bardarbunga and Grimsvotn volcanic alluvial plain (S). systems are among the most productive sys­ The central area of tems in Iceland and have fed some of its larg­ the Iceland hotspot is est fissure eruptions; for example, the Laki defined by the volca­ eruption in 1783. This eruption produced 12- 3 noes Bardarbunga, 14 km of basalt and was the largest lava erup­ Grimsvotn, Kverk­ tion ever witnessed by man. It had a fjoll, and Tung­ pronounced effect on the climate, particu- nafellsjokull. Glaciers are shaded Pall Einarsson, Bryndis Brandsdottir, Magnus Tumi Gudmundsson, and Helgi Bjornsson, Sci­ in gray. The box ence Institute, University of Iceland, Dunhaga shows the area de­ 3, 107 Reykjavik, Iceland; and Karl Grinvold, picted in Figure 2. Freysteinn Sigmundsson Nordic Volcanological Institute, University of Iceland, Grensasvegi 50, 108 Reykjavik, Iceland This page may be freely copied. Eos, Vol. 78, No. 35, Spetember 2, 1997 craft. By that time two elongate 1-2-km-wide, northeast trending subsidence cauldrons had formed on the ice surface south-south­ east of Bardarbunga (Figure 3a) on the north­ ern flank of the neighboring Grimsvotn volcano. The cauldron formation showed that the glacier was being melted by an erup­ tion on a 4-km-long fissure at the base of the glacier, which was 400-600 m thick. The northern cauldron deepened some 50 m in 4 hours. The fissure was located within the drainage basin of the Grimsvotn caldera caus­ ing the meltwater from the eruption to drain into the caldera lake. A shallow linear subsi­ dence structure was visible at the glacier sur­ face, marking the subglacial pathway of the meltwater draining into the Grimsvotn cal­ dera. The cauldrons widened and deepened during the day, and the level of the Grimsvotn lake rose by 10-15 m. About 0.3 km3 of water was added to the lake during the first 15 hours of the eruption. The vigor of the eruption could be monitored in three different ways; that is, by the volume of the depressions in the ice caused by the melting, by the volume of meltwater accumulating in the Grimsvotn caldera, and by the intensity of 0 20 km the volcanic tremor. Fig. 2. Map of the northwest Vatnajokull area, showing bedrock topography mapped by radio echo sounding, epicenters of earthquakes September 29-30 (dots), and the eruption fissure of The eruption was most powerful during 1996 (thick bent line near center). The calderas of the Bardarbunga and Grimsvotn volcanoes are the first 4 days. Most of the activity was hid­ clearly seen in the topography, as well as a hint of a larger circular structure (dashed line). The den below the glacier, but in the morning of seismic stations of Vonarskard and Grfmsfjall, shown with stars, provided invaluable data on the October 2 an opening formed in the glacier seismicity accompanying the eruption and the ensuing flood. The thin wavy line in the northwest surface, through which an eruptive column corner is the glacier margin. rose to 4-5 km altitude. Later that day the eruptive fissure extended some 3 km farther to the north. Ash dispersed to the north and The ice thickness reaches 800-900 m in lease when the water load was removed from colored the glacier surface (Figure 3b). The places, but the average thickness is 400 m. the caldera floor. The latest event of this type opening in the glacier grew larger in the fol­ The glacier, which has a surface area of occurred in 1934. lowing days and the subsidence area grew to 8200 km , covers some of Iceland's highest Jokulhlaups can also occur as the result 9 km long and 3-4 km wide. An ice canyon and most active volcanoes. These volcanoes of eruptions. An eruption in 1938 on the melted along the central axis of the depres­ erupted frequently throughout historic time, northern flank of Grimsvotn formed a sub­ sion (Figure 3c). Water flowed southward but few direct observations have been made. glacial ridge, which coincides with the south­ along the canyon toward the Grimsvotn cal­ ern part of the 1996 eruptive fissure dera. The volcanic tremor stopped on Octo­ The Grimsvotn caldera has an active geo- [Bjornsson, 1988; Gudmundsson and Bjorns­ ber 13, indicating that magma transport to thermal system, which melts ice at the rate of 3 son, 1991]. The 1938 eruption was almost en­ the eruption site had ceased. 0.2-0.5 km /yr during normal times [Bjorns­ son and Gudmundsson, 1993; Gudmundsson tirely subglacial, breaching the glacier A schematic section of the subglacial et al., 1995]. The water is contained by an ice surface shortly at the end of the eruption. The eruption and the path of the meltwater is dam that closes an outlet in the eastern cal­ meltwater drained into the Grimsvotn cal­ shown in Figure 4. The length of the main 3 dera wall, so the 250-m-thick ice shelf that dera, causing a large flood of -4.7 km , eruptive fissure was 7 km, but in addition a floats on the caldera lake rises -10-15 m per [Bjornsson, 1992, Gudmundsson etal, 1995].
Load more

Recommended publications
  • Volcanic Ash Over Europe During the Eruption of Eyjafjallajökull on Iceland, April–May 2010 In: Atmospheric Environment (2011) Elsevier
    Final Draft of the original manuscript: Langmann, B.; Folch, A.; Hensch, M.; Matthias, V.: Volcanic ash over Europe during the eruption of Eyjafjallajökull on Iceland, April–May 2010 In: Atmospheric Environment (2011) Elsevier DOI: 10.1016/j.atmosenv.2011.03.054 1 Volcanic ash over Europe during the eruption of Eyjafjallajökull on Iceland, 2 April-May 2010 3 4 Baerbel Langmann1), Arnau Folch2), Martin Hensch3) and Volker Matthias4) 5 6 1) Institute of Geophysics, University of Hamburg, KlimaCampus, Hamburg, Germany, 7 e-mail: [email protected] 8 2) Barcelona Supercomputing Center - Centro Nacional de Supercomputación, Barcelona, 9 Spain, e-mail: [email protected] 10 3) Nordic Volcanological Center, University of Iceland, Reykjavik, Iceland, e-mail: 11 [email protected] 12 4) Institute of Coastal Research, Helmholtz-Zentrum Geesthacht, Geesthacht, Germany, 13 e-mail: [email protected] 14 15 Abstract 16 During the eruption of Eyjafjallajökull on Iceland in April/May 2010, air traffic over Europe 17 was repeatedly interrupted because of volcanic ash in the atmosphere. This completely 18 unusual situation in Europe leads to the demand of improved crisis management, e.g. 19 European wide regulations of volcanic ash thresholds and improved forecasts of theses 20 thresholds. However, the quality of the forecast of fine volcanic ash concentrations in the 21 atmosphere depends to a great extent on a realistic description of the erupted mass flux of fine 22 ash particles, which is rather uncertain. Numerous aerosol measurements (ground based and 23 satellite remote sensing, and in situ measurements) all over Europe have tracked the volcanic 24 ash clouds during the eruption of Eyjafjallajökull offering the possibility for an 25 interdisciplinary effort between volcanologists and aerosol researchers to analyse the release 26 and dispersion of fine volcanic ash in order to better understand the needs for realistic 27 volcanic ash forecasts.
    [Show full text]
  • Iceland Is Cool: an Origin for the Iceland Volcanic Province in the Remelting of Subducted Iapetus Slabs at Normal Mantle Temperatures
    Iceland is cool: An origin for the Iceland volcanic province in the remelting of subducted Iapetus slabs at normal mantle temperatures G. R. Foulger§1 & Don L. Anderson¶ §Department of Geological Sciences, University of Durham, Science Laboratories, South Rd., Durham, DH1 3LE, U.K. ¶California Institute of Technology, Seismological Laboratory, MC 252-21, Pasadena, CA 91125, U. S. A. Abstract The time-progressive volcanic track, high temperatures, and lower-mantle seismic anomaly predicted by the plume hypothesis are not observed in the Iceland region. A model that fits the observations better attributes the enhanced magmatism there to the extraction of melt from a region of upper mantle that is at relatively normal temperature but more fertile than average. The source of this fertility is subducted Iapetus oceanic crust trapped in the Caledonian suture where it is crossed by the mid-Atlantic ridge. The extraction of enhanced volumes of melt at this locality on the spreading ridge has built a zone of unusually thick crust that traverses the whole north Atlantic. Trace amounts of partial melt throughout the upper mantle are a consequence of the more fusible petrology and can explain the seismic anomaly beneath Iceland and the north Atlantic without the need to appeal to very high temperatures. The Iceland region has persistently been characterised by complex jigsaw tectonics involving migrating spreading ridges, microplates, oblique spreading and local variations in the spreading direction. This may result from residual structural complexities in the region, inherited from the Caledonian suture, coupled with the influence of the very thick crust that must rift in order to accommodate spreading-ridge extension.
    [Show full text]
  • Disaster Aid After the 1783 Laki Eruption
    Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 25 June 2020 doi:10.20944/preprints202001.0070.v2 Haze, Hunger, Hesitation: Disaster aid after the 1783 Laki eruption Claudia E. Wieners ∗ aInstitute of Economics, Scuola Superiore Sant’Anna, Pisa, Italy bCentre for Complex Systems Studies, Utrecht University, Netherlands Abstract The 1783-1784 Laki eruption was one of the most severe natural catastrophes to occur in Iceland in historical times (since 1140 years). Vegetation damage by sulphate aerosol and fluorine poisoning caused a massive decimation of live- stock. The impact of fluorine poisoning and sulphate aerosol on human mortal- ity is uncertain, but the loss of animals caused a famine which took many lives. The vulnerability of the Icelandic society to famine is discussed. 18th Century Iceland was a Danish dependency and, despite the abundance of fish in the surrounding waters, a subsistence farming community and thus highly depen- dent on livestock. On the other hand, the farming community possessed coping strategies which mitigated the impact of livestock loss. During the famine, the Danish government was in principle willing to provide relief. However, local authorities in Iceland were slow to ask for help, and did not dare to exploit the means at their disposal (e.g. the right to ban the export of Icelandic foodstuff) without consent from Copenhagen. The Danish officials in turn were unwill- ing to act decisively upon incomplete information. These two factors prevented timely measures. While 4:4 × 105kg of grain were provided for famine relief in summer 1784, the merchants exported 1:2 × 106kg of fish, which greatly aggra- vated the hunger in the second winter.
    [Show full text]
  • 1783-84 Laki Eruption, Iceland
    1783-84 Laki eruption, Iceland Eruption History and Atmospheric Effects Thor Thordarson Faculty of Earth sciences, University of Iceland 12/8/2017 1 Atmospheric Effects of the 1783-84 Laki Eruption in Iceland Outline . Volcano-Climate interactions - background Laki eruption . Eruption history . Sulfur release and aerosol loading . Plume transport and aerosol dispersal . Environmental and climatic effects 12/8/2017. Concluding Remarks 2 Santorini, 1628 BC Tambora, 1815 Etna, 44 BC Lakagígar, 1783 Toba, 71,000 BP Famous Volcanic Eruptions Krakatau, 1883 Pinatubo, 1991 El Chichón, 1982 Agung, 1963 St. Helens, 1980 Major volcanic eruptions of the past 250 years Volcano Year VEI d.v.i/Emax IVI Lakagígar [Laki craters], Iceland 1783 4 2300 0.19 Unknown (El Chichón?) 1809 0.20 Tambora, Sumbawa, Indonesia 1815 7 3000 0.50 Cosiguina, Nicaragua 1835 5 4000 0.11 Askja, Iceland 1875 5 1000 0.01* Krakatau, Indonesia 1883 6 1000 0.12 Okataina [Tarawera], North Island, NZ 1886 5 800 0.04 Santa Maria, Guatemala 1902 6 600 0.05 Ksudach, Kamchatka, Russia 1907 5 500 0.02 Novarupta [Katmai], Alaska, US 1912 6 500 0.15 Agung, Bali, Indonesia 1963 4 800 0.06 Mt. St. Helens, Washington, US 1980 5 500 0.00 El Chichón, Chiapas, Mexico 1982 5 800 0.06 Mt. Pinatubo, Luzon, Philippines 1991 6 1000 — Volcano – Climate Interactions Key to Volcanic Forcing is: SO2 mass loading, eruption duration plume height replenishment aerosol production, residence time 12/8/2017 5 Volcanic Forcing: sulfur dioxide sulfate aerosols SO2 75%H2SO4+ 25%H2O clear sky 1991 Pinatubo aerosols
    [Show full text]
  • The Iceland–Jan Mayen Plume System and Its Impact on Mantle Dynamics in the North Atlantic Region: Evidence from Full-Waveform Inversion
    Earth and Planetary Science Letters 367 (2013) 39–51 Contents lists available at SciVerse ScienceDirect Earth and Planetary Science Letters journal homepage: www.elsevier.com/locate/epsl The Iceland–Jan Mayen plume system and its impact on mantle dynamics in the North Atlantic region: Evidence from full-waveform inversion Florian Rickers n, Andreas Fichtner, Jeannot Trampert Department of Earth Sciences, Utrecht University, Budapestlaan 4, 3584 CD, Utrecht, The Netherlands article info abstract Article history: We present a high-resolution S-velocity model of the North Atlantic region, revealing structural Received 22 October 2012 features in unprecedented detail down to a depth of 1300 km. The model is derived using full- Received in revised form waveform tomography. More specifically, we minimise the instantaneous phase misfit between 25 January 2013 synthetic and observed body- as well as surface-waveforms iteratively in a full three-dimensional, Accepted 16 February 2013 adjoint inversion. Highlights of the model in the upper mantle include a well-resolved Mid-Atlantic Editor: Y. Ricard Ridge and two distinguishable strong low-velocity regions beneath Iceland and beneath the Kolbeinsey Ridge west of Jan Mayen. A sub-lithospheric low-velocity layer is imaged beneath much of the oceanic Keywords: lithosphere, consistent with the long-wavelength bathymetric high of the North Atlantic. The low- seismology velocity layer extends locally beneath the continental lithosphere of the southern Scandinavian full-waveform inversion Mountains, the Danish Basin, part of the British Isles and eastern Greenland. All these regions North Atlantic mantle plumes experienced post-rift uplift in Neogene times, for which the underlying mechanism is not well Iceland understood.
    [Show full text]
  • The Impacts of a Laki-Like Eruption on the Present Swedish Society
    http://www.diva-portal.org This is the published version of a paper published in Natural Hazards. Citation for the original published paper (version of record): Sonnek, K M., Martensson, T., Veiback, E., Tunved, P., Grahn, H. et al. (2017) The impacts of a Laki-like eruption on the present Swedish society. Natural Hazards, 88(3): 1565-1590 https://doi.org/10.1007/s11069-017-2933-0 Access to the published version may require subscription. N.B. When citing this work, cite the original published paper. Permanent link to this version: http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-142876 Nat Hazards (2017) 88:1565–1590 DOI 10.1007/s11069-017-2933-0 ORIGINAL PAPER The impacts of a Laki-like eruption on the present Swedish society 1 2 Karin Mossberg Sonnek • Tomas Ma˚rtensson • 1 3 4 Ester Veiba¨ck • Peter Tunved • Ha˚kan Grahn • 4 4 Pontus von Schoenberg • Niklas Bra¨nnstro¨m • Anders Bucht4,5 Received: 16 May 2016 / Accepted: 18 May 2017 / Published online: 31 May 2017 Ó The Author(s) 2017. This article is an open access publication Abstract In this study, we analyse and discuss the possible impacts on the Swedish society of a volcanic eruption on Iceland, emitting ash particles and large quantities of sulphur dioxide. A scenario was developed, based on the historical Laki eruption of 1783–1784, to describe the content of a potential sulphur fog over time in Sweden. Due to its high complexity and the many uncertainties in the underpinning scientific data, the scenario was developed using a cross-disciplinary approach incorporating experts from different scien- tific fields.
    [Show full text]
  • Aula 4 – Tipos Crustais Tipos Crustais Continentais E Oceânicos
    14/09/2020 Aula 4 – Tipos Crustais Introdução Crosta e Litosfera, Astenosfera Crosta Oceânica e Tipos crustais oceânicos Crosta Continental e Tipos crustais continentais Tipos crustais Continentais e Oceânicos A interação divergente é o berço fundamental da litosfera oceânica: não forma cadeias de montanhas, mas forma a cadeia desenhada pela crista meso- oceânica por mais de 60.000km lineares do interior dos oceanos. A interação convergente leva inicialmente à formação dos arcos vulcânicos e magmáticos (que é praticamente o berço da litosfera continental) e posteriormente à colisão (que é praticamente o fechamento do Ciclo de Wilson, o desparecimento da litosfera oceânica). 1 14/09/2020 Curva hipsométrica da terra A área de superfície total da terra (A) é de 510 × 106 km2. Mostra a elevação em função da área cumulativa: 29% da superfície terrestre encontra-se acima do nível do mar; os mais profundos oceanos e montanhas mais altas uma pequena fração da A. A > parte das regiões de plataforma continental coincide com margens passivas, constituídas por crosta continental estirada. Brito Neves, 1995. Tipos crustais circunstâncias geométrico-estruturais da face da Terra (continentais ou oceânicos); Característica: transitoriedade passar do Tempo Geológico e como forma de dissipar o calor do interior da Terra. Todo tipo crustal adveio de um outro ou de dois outros, e será transformado em outro ou outros com o tempo, toda esta dança expressando a perda de calor do interior para o exterior da Terra. Nenhum tipo crustal é eterno; mais "duráveis" (e.g. velhos Crátons de de "ultra-longa duração"); tipos de curta duração, muitas modificações e rápida evolução potencial (como as bacias de antearco).
    [Show full text]
  • 98-031 Oceanus F/W 97 Final
    A hotspot created the island of Iceland and its characteristic volcanic landscape. Hitting the Hotspots Hotspots are rela- tively small regions on the earth where New Studies Reveal Critical Interactions unusually hot rocks rise from deep inside Between Hotspots and Mid-Ocean Ridges the mantle layer. Jian Lin Associate Scientist, Geology & Geophysics Department he great volcanic mid-ocean ridge system hotspots may play a critical role in shaping the stretches continuously around the globe for seafloor—acting in some cases as strategically T 60,000 kilometers, nearly all of it hidden positioned supply stations that fuel the lengthy beneath the world’s oceans. In some places, how- mid-ocean ridges with magma. ever, mid-ocean ridge volcanoes are so massive that Studies of ridge-hotspot interactions received a they emerge above sea level to create some of the major boost in 1995 when the US Navy declassified most spectacular islands on our planet. Iceland, the gravity data from its Geosat satellite, which flew Azores, and the Galápagos are examples of these from 1985 to 1990. The satellite recorded in unprec- “hotspot” islands—so named because they are edented detail the height of the ocean surface. With believed to form above small regions scattered accuracy within 5 centimeters, it revealed small around the earth where unusually hot rocks rise bumps and dips created by the gravitational pull of from deep inside the mantle layer. dense underwater mountains and valleys. Research- But hotspots may not be such isolated phenom- ers often use precise gravity measurements to probe ena. Exciting advances in satellite oceanography, unseen materials below the ocean floor.
    [Show full text]
  • Atmospheric and Environmental Effects of the 1783–1784 Laki Eruption: a Review and Reassessment
    JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, NO. D1, 4011, doi:10.1029/2001JD002042, 2003 Atmospheric and environmental effects of the 1783–1784 Laki eruption: A review and reassessment Thorvaldur Thordarson1 and Stephen Self 2 Department of Geology and Geophysics, School of Ocean and Earth Sciences and Technology, University of Hawaii at Manoa, Honolulu, Hawaii, USA Received 27 December 2001; revised 5 April 2002; accepted 8 April 2002; published 8 January 2003. [1] The 1783–1784 Laki flood lava eruption in Iceland emitted 122 megatons (Mt) SO2 into the atmosphere and maintained a sulfuric aerosol veil that hung over the Northern Hemisphere for >5 months. The eruption columns extended to 9–13 km and released 95 Mt SO2 into the upper troposphere/lower stratosphere (i.e., the polar jet stream), enforcing a net eastward dispersion of the plumes which reacted with atmospheric moisture to produce 200 Mt of H2SO4 aerosols. Away from source, the Laki aerosols were delivered to the surface by subsiding air masses within anticyclones. We show that 175 Mt of H2SO4 aerosols were removed as acid precipitation and caused the extreme volcanic pollution (i.e., dry fog) that effected Europe and other regions in 1783. The remaining 25 Mt stayed aloft at tropopause level for >1 year. The summer of 1783 was characterizedby extreme and unusual weather, including an unusually hot July in western Europe, most likely caused by perseverance of southerly air currents. The following winter was one of the most severe winters on record in Europe and North America. In these regions, the annual mean surface cooling that followed the Laki eruption was about 1.3°C and lasted for 2–3 years.
    [Show full text]
  • Preventing Ice Dams
    {Property} Preventing Ice Dams waterWhat CAU Recommends: Introduction > Clean rain gutters annually to Ice dams represent a costly (and potentially remove obstructions that can dangerous) hazard for property owners and block the flow of water from community associations. Even worse, once a the roof building has shown itself to be susceptible to ice > Inspect attic insulation and dams, it is more likely to keep developing them ventilation during future cold weather. > Install ice shields or other waterproof membranes The majority of ice dams form as a ridge of ice beneath the roof covering along a rain gutter and roof eave. As ice builds during roof replacement up, it creates an unintended dam that prevents projects melting snow from draining off of the roof. Some > Locate a contractor that can can be very easy to see, but others form around clear ice dams from your skylights, chimneys, and other features that make buildings them harder to detect from the ground. Need More Information? Whether they are visible or not, ice dams can Additional information relating cause significant damage to a building or unit. to ice dam prevention is That’s because water that pools up behind it can available from The Institute find its way under the roof and into the structure for Business and Home Safety and the interior of a home. It isn’t unusual for (www.disastersafety.org) or by ice dams to cause damage to insulation, wall contacting CAU’s Loss Control interiors, ceiling finishes, and trim. Exterior Department. damage to roofs, gutters, and spaces below an ice dam (like windows and landscaping) is also common.
    [Show full text]
  • Ice Dams: Formations and Fixes 1St Edition
    Ice Dams: Formations and Fixes 1st Edition 516.621.2900 • [email protected] • jsheld.com Copyright © 2018 J.S. Held LLC, All rights reserved. TECHNICAL TOPICS As we approach the cooler change of seasons, we look forward to many things; the stunning change of foliage, football, and atmospheric water vapor frozen into ice crystals and falling in light white flakes, more commonly known as snow. If you live in the north, you’ve probably had anywhere from a few inches to several feet of snow at one time or another. If you have experienced snow accumulation, freezing temperatures, and certain building conditions, you may have been the recipient of an ice dam. The term “ice dam” refers to the damming of water behind an accumulation of ice buildup along the eaves and/or valleys on a roof covered with snow. Heat loss into the attic space or rafter cavities warms the roof deck and causes snow to melt. As this melted water makes it way to the eaves, it freezes at the eaves as there is no heat loss in this area. This can lead to a buildup of ice and a backup of water, hence the term “ice dam”. See Figure 1 below for additional details. Within this paper we review the cause of ice dams, steps to prevent their formation, and mitigation of damage when an ice dam forms. We will also review ANSI/IICRC standards to determine the categorization of water from ice dams. Ice Dam Basics There are a few key points that differentiate an ice dam condition from typical snow accumulation on a roof: • The outside temperatures must be below freezing for a duration long enough to allow freezing at the roof edge to occur.
    [Show full text]
  • The Eruption on Heimaey, Vestmannaeyjar, Iceland
    Man Against Volcano: The Eruption on Heimaey, Vestmannaeyjar, Iceland This booklet was originally published in 1976 under the title "Man Against Volcano: The Eruption on Heimaey, Vestmann Islands, Iceland." The revised second edition was published in 1983. This PDF file is a recreation of the 1983 booklet. Cover photograph: View looking southeast along streets covered by tephra (volcanic ash) in Vestmannaeyjar: Eldfell volcano (in background) is erupting and fountaining lava. View of Heimaey before the eruption: Town of Vestmannaeyjar with Helgafell in the right back- ground (photo courtesy of Sólarfilma). Man Against Volcano: The Eruption on Heimaey, Vestmannaeyjar, Iceland by Richard S. Williams, Jr., and James G. Moore Preface The U.S. Geological Survey carries out scientific studies in the geological, hydrological, and cartographic sciences generally within the 50 States and its territories or trusteeships, but also in cooperation with scientific organizations in many foreign countries for the investigation of unusual earth sciences phenome- na throughout the world. In 1983, the U.S. Geological Survey had 57 active sci- entific exchange agreements with 24 foreign countries, and 47 scientific exchange agreements were pending with 30 foreign countries. The following material discusses the impact of the 1973 volcanic eruption of Eldfell on the fishing port of Vestmannaeyjar on the island of Heimaey, Vestmannaeyjar, Iceland. Before the eruption was over, approximately one-third of the town of Vestmannaeyjar had been obliterated, but, more importantly, the potential damage probably was reduced by the spraying of seawater onto the advancing lava flows, causing them to be slowed, stopped, or diverted from the undamaged portion of the town.
    [Show full text]