World Heritage Volcanoes a Thematic Study: a Global Review of Volcanic World Heritage Properties: Present Situation, Future Prospects and Management Requirements

Total Page:16

File Type:pdf, Size:1020Kb

World Heritage Volcanoes a Thematic Study: a Global Review of Volcanic World Heritage Properties: Present Situation, Future Prospects and Management Requirements World Heritage Volcanoes A thematic study: A Global Review of Volcanic World Heritage Properties: Present Situation, Future Prospects and Management Requirements IUCN Protected Areas Programme - World Heritage Studies About IUCN IUCN, International Union for Conservation of Nature, helps the world fi nd pragmatic solutions to our most pressing environment and development challenges. IUCN works on biodiversity, climate change, energy, human livelihoods and greening the world economy by supporting scientifi c research, managing fi eld projects all over the world, and bringing governments, NGOs, the UN and companies together to develop policy, laws and best practice. IUCN is the world’s oldest and largest global environmental organization, with more than 1,000 government and NGO members and almost 11,000 volunteer experts in some 160 countries. IUCN’s work is supported by over 1,000 staff in 60 offi ces and hundreds of partners in public, NGO and private sectors around the world. www.iucn.org This study is produced as part of IUCN’s role as advisory body to the UNESCO World Heritage Convention on natural heritage. Acknowledgements This report has benefi ted from research of databases undertaken with the assistance of Jessica Roberts. In addition, thanks are extended to a number of external reviewers of this document. Nevertheless, any errors or inaccuracies remain the sole responsibility of the author. IUCN Programme on Protected Areas Rue Mauverney 28 CH-1196 Gland Switzerland www.iucn.org/wcpa The designation of geographical entities in this book, and the presentation of the material, do not imply the expression of any opinion whatsoever on the part of IUCN concerning the legal status of any country, territory, or area, or of its authorities, or concerning the delimitation of its frontiers or boundaries. The views expressed in this publication do not necessarily refl ect those of IUCN. Published by: IUCN, Gland, Switzerland Copyright: © 2009 International Union for Conservation of Nature and Natural Resources Reproduction of this publication for educational or other non-commercial purposes is authorized without prior written permission from the copyright holder provided the source is fully acknowledged. Reproduction of this publication for resale or other commercial purposes is prohibited without prior written permission of the copyright holder. Citation: Chris Wood. World Heritage Volcanoes, Gland, Switzerland: IUCN. 70pp. Cover photo: June 1996 eruption of Mt Ruapehu, which is one of four andesitic volcanoes in New Zealand’s Tongariro National Park, a World Heritage Cultural Landscape. © Harry Keys Layout by: Delwyn Dupuis Produced by: IUCN Protected Areas Programme Printed by: IUCN Available from: IUCN (International Union for Conservation of Nature) Publications Services Rue Mauverney 28 1196 Gland Switzerland Tel +41 22 999 0000 Fax +41 22 999 0020 [email protected] www.iucn.org/publications A catalogue of IUCN publications is also available. The text of this book is printed on paper made from wood fi bre from well-managed forests certifi ed in accordance with the rules of the Forest Stewardship Council (FSC). World Heritage Volcanoes A thematic study: A Global Review of Volcanic World Heritage Properties: Present Situation, Future Prospects and Management Requirements Table of Contents Summary ...........................................................................................................................................................1 Introduction ........................................................................................................................................................3 The purpose of the study ...................................................................................................................................5 Defi ning the scope of the study .........................................................................................................................7 What is a volcanic World Heritage property? ......................................................................................7 What is an active volcano? .................................................................................................................8 Volcanoes are complex constructions ...............................................................................................11 Chemical change in the magma chamber.........................................................................................11 Degraded volcanic cones and domes ...............................................................................................11 Exposed intrusive forms ....................................................................................................................11 Hydrothermal phenomena and solfataric fi elds .................................................................................13 Volcanoes on the ocean fl oors ..........................................................................................................13 Summary of scope of study...............................................................................................................14 Volcanoes and volcanic features on the World Heritage List ..........................................................................15 Types of volcanic World Heritage properties .....................................................................................16 Number of Holocene volcanoes in World Heritage properties ..........................................................17 Archaeological sites and settlements periodically buried by volcanic deposits ................................18 Atolls and reef-fringed islands ...........................................................................................................18 Technical framework for gap analysis..............................................................................................................19 Genetic classifi cation ........................................................................................................................19 Styles of eruption ..............................................................................................................................20 Plate tectonic setting .........................................................................................................................21 Classifi cations of volcanic landforms ................................................................................................25 Conclusion: a framework for gap analysis ........................................................................................26 Identifying the gaps .........................................................................................................................................27 Gaps in the range of volcanic World Heritage properties ..................................................................27 Missing iconic volcanoes...................................................................................................................31 Filling the gaps ................................................................................................................................................32 Requirements for integrity and management that should apply to sites with volcanic geology .......................33 Meeting the condition of Integrity ......................................................................................................33 Example 1 - Jeju Volcanic Island, Republic of Korea ........................................................................34 Example 2 - Teide National Park, Tenerife, Spain .............................................................................35 Site management .............................................................................................................................36 Education and interpretation .............................................................................................................37 Monitoring .........................................................................................................................................37 Risk management and contingency planning ...................................................................................39 Conclusions and Recommendations ...............................................................................................................41 Annexes Annex 1: List of Figures ....................................................................................................................43 Annex 2: List of Tables .....................................................................................................................44 Annex 3: Data Sources ...................................................................................................................45 Annex 4: References ........................................................................................................................46 Annex 5: Glossary ............................................................................................................................47 Annex 6: Table 1 Properties with volcanic geology on the World Heritage List ................................52 Annex 7: Table 2 Properties with volcanic geology on the Tentative Lists........................................58 Summary This Global Theme Study examines the position of volcanoes and volcanic features in relation to the World Heritage List. It
Recommended publications
  • Geologic Map of the Central San Juan Caldera Cluster, Southwestern Colorado by Peter W
    Geologic Map of the Central San Juan Caldera Cluster, Southwestern Colorado By Peter W. Lipman Pamphlet to accompany Geologic Investigations Series I–2799 dacite Ceobolla Creek Tuff Nelson Mountain Tuff, rhyolite Rat Creek Tuff, dacite Cebolla Creek Tuff Rat Creek Tuff, rhyolite Wheeler Geologic Monument (Half Moon Pass quadrangle) provides exceptional exposures of three outflow tuff sheets erupted from the San Luis caldera complex. Lowest sheet is Rat Creek Tuff, which is nonwelded throughout but grades upward from light-tan rhyolite (~74% SiO2) into pale brown dacite (~66% SiO2) that contains sparse dark-brown andesitic scoria. Distinctive hornblende-rich middle Cebolla Creek Tuff contains basal surge beds, overlain by vitrophyre of uniform mafic dacite that becomes less welded upward. Uppermost Nelson Mountain Tuff consists of nonwelded to weakly welded, crystal-poor rhyolite, which grades upward to a densely welded caprock of crystal-rich dacite (~68% SiO2). White arrows show contacts between outflow units. 2006 U.S. Department of the Interior U.S. Geological Survey CONTENTS Geologic setting . 1 Volcanism . 1 Structure . 2 Methods of study . 3 Description of map units . 4 Surficial deposits . 4 Glacial deposits . 4 Postcaldera volcanic rocks . 4 Hinsdale Formation . 4 Los Pinos Formation . 5 Oligocene volcanic rocks . 5 Rocks of the Creede Caldera cycle . 5 Creede Formation . 5 Fisher Dacite . 5 Snowshoe Mountain Tuff . 6 Rocks of the San Luis caldera complex . 7 Rocks of the Nelson Mountain caldera cycle . 7 Rocks of the Cebolla Creek caldera cycle . 9 Rocks of the Rat Creek caldera cycle . 10 Lava flows premonitory(?) to San Luis caldera complex . .11 Rocks of the South River caldera cycle .
    [Show full text]
  • Atlas of the World 1 SECONDARY
    Atlas of the World 1 SECONDARY Atlas of the World is a collective work, conceived, designed and created by the bilingual department at Santillana, under the supervision of Teresa Grence. WRITER Pilar Moralejo EDITORS Sara J. Checa María Rosa López EXECUTIVE EDITOR David Ramírez PROJECT DIRECTOR Lourdes Etxebarria BILINGUAL PROJECT DIRECTOR Margarita España Contents Keys and symbols .................................................................................................... 3 World maps Physical map of the world ....................................................................................... 4 Continents Physical map of Europe ............................................................................................. 6 Political map of Europe .............................................................................................. 8 Climates and vegetation of Europe ......................................................................... 10 Physical map of Asia ................................................................................................ 12 Political map of Asia ................................................................................................. 14 Climates and vegetation of Asia .............................................................................. 16 Physical map of Africa ............................................................................................. 18 Political map of Africa ............................................................................................
    [Show full text]
  • Moüjmtaiim Operations
    L f\f¿ áfó b^i,. ‘<& t¿ ytn) ¿L0d àw 1 /1 ^ / / /This publication contains copyright material. *FM 90-6 FieW Manual HEADQUARTERS No We DEPARTMENT OF THE ARMY Washington, DC, 30 June 1980 MOÜJMTAIIM OPERATIONS PREFACE he purpose of this rUanual is to describe how US Army forces fight in mountain regions. Conditions will be encountered in mountains that have a significant effect on. military operations. Mountain operations require, among other things^ special equipment, special training and acclimatization, and a high decree of self-discipline if operations are to succeed. Mountains of military significance are generally characterized by rugged compartmented terrain witn\steep slopes and few natural or manmade lines of communication. Weather in these mountains is seasonal and reaches across the entireSspectrum from extreme cold, with ice and snow in most regions during me winter, to extreme heat in some regions during the summer. AlthoughNthese extremes of weather are important planning considerations, the variability of weather over a short period of time—and from locality to locahty within the confines of a small area—also significantly influences tactical operations. Historically, the focal point of mountain operations has been the battle to control the heights. Changes in weaponry and equipment have not altered this fact. In all but the most extreme conditions of terrain and weather, infantry, with its light equipment and mobility, remains the basic maneuver force in the mountains. With proper equipment and training, it is ideally suited for fighting the close-in battfe commonly associated with mountain warfare. Mechanized infantry can\also enter the mountain battle, but it must be prepared to dismount and conduct operations on foot.
    [Show full text]
  • Temporal Evolution of the Barombi Mbo Maar, a Polygenetic Maar-Diatreme Volcano of the Cameroon Volcanic Line*
    International Journal of Geosciences, 2014, 5, 1315-1323 Published Online October 2014 in SciRes. http://www.scirp.org/journal/ijg http://dx.doi.org/10.4236/ijg.2014.511108 Temporal Evolution of the Barombi Mbo Maar, a Polygenetic Maar-Diatreme Volcano of the Cameroon Volcanic Line* Boris Chako Tchamabé1#, Takeshi Ohba1, Issa1, Seigo Ooki1, Dieudonné Youmen2, Sebastien Owona2, Gregory Tanyileke3, Joseph Victor Hell3 1Laboratory of Volcanology and Geochemistry, Department of Chemistry, Tokai University, Tokyo, Japan 2Department of Earth Science, Faculty of Sciences, University of Douala, Douala, Cameroon 3Institute of Mining and Geological Research (IRGM), Yaoundé, Cameroon Email: #[email protected] Received 1 August 2014; revised 25 August 2014; accepted 15 September 2014 Copyright © 2014 by authors and Scientific Research Publishing Inc. This work is licensed under the Creative Commons Attribution International License (CC BY). http://creativecommons.org/licenses/by/4.0/ Abstract The Barombi Mbo Maar (BMM), which is the largest maar in Cameroon, possesses about 126 m- thick well-preserved pyroclastic deposits sequence in which two successive paleosoil beds have been identified. The maar was thought to have been active a million years ago. However, layers stratigraphically separated by the identified paleosoils have been dated to shed lights on its age and to reconstruct the chronology of its past activity. The results showed that the BMM formed through three eruptive cycles: the first ~0.51 Ma ago, the second at ~0.2 Ma and the third ~0.08 Ma B.P. The ages indicate that the BMM maar-forming eruptions were younger than a million years. The findings also suggested that the maar is polygenetic.
    [Show full text]
  • The Mineralogy and Chemistry of the Anorogenic Tertiary Silicic Volcanics
    JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 86, NO. Bll, PAGES 10242-10256, NOVEMBER 10, 1981 The Mineralogyand Chemistryof the AnorogenicTertiary SilicicVolcanics of S.E. Queenslandand N.E. New South Wales, Australia A. EWART Departmentof Geology& Mineralogy,University of Queensland,St. Lucia,Brisbane, Queensland 4067 The Late Oligocene-EarlyMiocene volcanismof this regionis chemicallystrongly bimodal; the mafic lavas(volmetrically dominant) comprise basalts, hawaiites, and tholeiiticandesites, while the silicic eruptivesare mainly comendites,potassic trachytes, and potassic,high-silica rhyolites.The comendites and rhyoliteshave distinctivetrace element abundancepatterns, notably the extreme depletionsof Sr, Ba, Mg, Mn, P, Cr, V, and Eu, and the variable em'ichraentof suchelements as Rb, Zr, Pb, Nb, Zn, U, and Th. The trachytesexhibit thesecharacteristics to lesserdegrees. The comenditesare distinguished from the rhyolitesby their overall relative enrichmentof the more highly chargedcations (e.g., LREE, Nb, Y, and especiallyZr) and Zn. The phenocrystmineralogy of the trachytesand rhyolitescomprises various combinationsof the following phases:sodic plagioclase(albite-andesine), calcic anorthoclase, sanidine, quartz, ferroaugite-ferrohedenbergite,ferrohypersthene, fayalitic olivine, ilmenite, titano- magnetite,and rarely biotite (near annite) and Fe-hastingsiticamphibole. Accessories include apatite, zircon, chevkinite (ferrohedenbergite-bearingrhyolites only), and allanite (amphibole and botite rhyo- lites only). The comenditesgenerally contain
    [Show full text]
  • Source to Surface Model of Monogenetic Volcanism: a Critical Review
    Downloaded from http://sp.lyellcollection.org/ by guest on September 28, 2021 Source to surface model of monogenetic volcanism: a critical review I. E. M. SMITH1 &K.NE´ METH2* 1School of Environment, University of Auckland, Auckland, New Zealand 2Volcanic Risk Solutions, Massey University, Palmerston North 4442, New Zealand *Correspondence: [email protected] Abstract: Small-scale volcanic systems are the most widespread type of volcanism on Earth and occur in all of the main tectonic settings. Most commonly, these systems erupt basaltic magmas within a wide compositional range from strongly silica undersaturated to saturated and oversatu- rated; less commonly, the spectrum includes more siliceous compositions. Small-scale volcanic systems are commonly monogenetic in the sense that they are represented at the Earth’s surface by fields of small volcanoes, each the product of a temporally restricted eruption of a composition- ally distinct batch of magma, and this is in contrast to polygenetic systems characterized by rela- tively large edifices built by multiple eruptions over longer periods of time involving magmas with diverse origins. Eruption styles of small-scale volcanoes range from pyroclastic to effusive, and are strongly controlled by the relative influence of the characteristics of the magmatic system and the surface environment. Gold Open Access: This article is published under the terms of the CC-BY 3.0 license. Small-scale basaltic magmatic systems characteris- hazards associated with eruptions, and this is tically occur at the Earth’s surface as fields of small particularly true where volcanic fields are in close monogenetic volcanoes. These volcanoes are the proximity to population centres.
    [Show full text]
  • Anatomy of a Volcanic Eruption: Case Study: Mt. St. Helens
    Anatomy of a Volcanic Eruption: Case Study: Mt. St. Helens Materials Included in this Box: • Teacher Background Information • 3-D models of Mt. St. Helens (before and after eruption) • Examples of stratovolcano rock products: Tuff (pyroclastic flow), pumice, rhyolite/dacite, ash • Sandbox crater formation exercise • Laminated photos/diagrams Teacher Background There are several shapes and types of volcanoes around the world. Some volcanoes occur on the edges of tectonic plates, such as those along the ‘ring of fire’. But there are also volcanoes that occur in the middle of tectonic plates like the Yellowstone volcano and Kilauea volcano in Hawaii. When asked to draw a volcano most people will draw a steeply sided, conical mountain that has a depression (crater) at the top. This image of a 'typical' volcano is called a stratovolcano (a.k.a. composite volcano). While this is the often visualized image of a volcano, there are actually many different shapes volcanoes can be. A volcano's shape is mostly determined by the type of magma/lava that is created underneath it. Stratovolcanoes get their shape because of the thick, sticky (viscous) magma that forms at subduction zones. This magma/lava is layered between ash, pumice, and rock fragments. These layers of ash and magma will build into high elevation, steeply sided, conical shaped mountains and form a 'typical' volcano shape. Stratovolcanoes are also known for their explosive and destructive eruptions. Eruptions can cause clouds of gas, ash, dust, and rock fragments to eject into the atmosphere. These clouds of ash can become so dense and heavy that they quickly fall down the side of the volcanoes as a pyroclastic flow.
    [Show full text]
  • MEKE MAAR / Republic of Turkey 1. Name and Adress of the Compiler Of
    MEKE MAAR / Republic of Turkey 1. Name and adress of the compiler of this form: Selim ERDOGAN (Hydrogeological Engineer, M.Sc) Ministry of Environment & Forestry., General Directorate of Nature Conservation & National Parks., Wetlands Division Address: Çevre ve Orman Bakanlığı, İstanbul Caddesi No: 98 Phone: 0090 312 3840510 / 3021 Fax: 0090 312 3842476 Email: [email protected] 2. Date this sheet was completed/updated 01.02.2006 3. Country: Republic of Turkey 4. Name of the Ramsar Site Meke Maar 5. Map of Site included A site map of 1:25 000 scale and providing the characteristics indicated in the Annex III of this guideline is included in this package. a) Hard Copy: YES b) Digital (electronic) Format: YES 6. Geographical Coordinates: 33038’28’’ E., 37041’10’’ N 7. General Location: Turkey is separated into 82 administrative districts. As regards area extension, Konya is the largest district of Turkey. It’s also the 4th biggest city with approximately 2 million habitants. Meke Maar is situated in Konya district. The distance of it to the center of the city is approximately 101 km (towards the south of the district). The subdivision in which the Meke Maar is located, is Karapınar and it’s 8 km far from the site. 8. Elevation: 1004 m (minimum – the elevation of the plain on which the maar is situated) 1280 m (maximum – the elevation of the crater of the volcano) 9. Area: 202 hectares 10. Overview: Meke Maar is a volcanic system which contains typically a volcanic rock mass and a crater lake up above. However the system differs from other volcanic systems with its caldera lake surrounding the volcanic mass (See pictures in Annex 2).
    [Show full text]
  • A Unique Volcanic Field in Tharsis, Mars: Monogenetic Cinder Cones and Lava Flows As Evidence for Hawaiian Eruptions
    42nd Lunar and Planetary Science Conference (2011) 1379.pdf A UNIQUE VOLCANIC FIELD IN THARSIS, MARS: MONOGENETIC CINDER CONES AND LAVA FLOWS AS EVIDENCE FOR HAWAIIAN ERUPTIONS. P. Brož1 and E. Hauber2, 1Institute of Geophysics ASCR, v.v.i., Prague, Czech Republic, [email protected], 2Institut für Planetenforschung, DLR, Berlin, Germany, [email protected]. Introduction: Most volcanoes on Mars that have Data: We use images from several cameras, i.e. been studied so far seem to be basaltic shield volca- Context Camera (CTX), High Resolution Stereo Cam- noes, which can be very large with diameters of hun- era (HRSC), and High Resolution Imaging Science dreds of kilometers [e.g., 1] or much smaller with di- Experiment (HiRISE) for morphological analyses. ameters of several kilometers only [2]. Few Viking Topographic information (e.g., heights and slope an- Orbiter-based studies reported the possible existence gles) were determined from single shots of the Mars of cinder cones [3,4] or stratovolcanoes [5-7], and only Orbiter Laser Altimeter (MOLA) in a GIS environ- the advent of higher-resolution data led to the tentative ment, and from stereo images (HRSC, CTX) and de- interpretation of previously unknown edifices as cinder rived gridded digital elevation models (DEM). cones [8] or rootless cones [9]. The identification of Morphometry: For comparison between the cinder cones can constrain the nature of eruption proc- cones and terrestrial morphological analogues (i.e. esses and, indirectly, our understanding of the nature cinder cones [10]) we determined some basic mor- of parent magmas (e.g., volatile content). Here we re- phometric properties and their ratios (e.g., crater di- port on our observation of a unique cluster of possible ameter [WCR] vs.
    [Show full text]
  • The Science Behind Volcanoes
    The Science Behind Volcanoes A volcano is an opening, or rupture, in a planet's surface or crust, which allows hot magma, volcanic ash and gases to escape from the magma chamber below the surface. Volcanoes are generally found where tectonic plates are diverging or converging. A mid-oceanic ridge, for example the Mid-Atlantic Ridge, has examples of volcanoes caused by divergent tectonic plates pulling apart; the Pacific Ring of Fire has examples of volcanoes caused by convergent tectonic plates coming together. By contrast, volcanoes are usually not created where two tectonic plates slide past one another. Volcanoes can also form where there is stretching and thinning of the Earth's crust in the interiors of plates, e.g., in the East African Rift, the Wells Gray-Clearwater volcanic field and the Rio Grande Rift in North America. This type of volcanism falls under the umbrella of "Plate hypothesis" volcanism. Volcanism away from plate boundaries has also been explained as mantle plumes. These so- called "hotspots", for example Hawaii, are postulated to arise from upwelling diapirs with magma from the core–mantle boundary, 3,000 km deep in the Earth. Erupting volcanoes can pose many hazards, not only in the immediate vicinity of the eruption. Volcanic ash can be a threat to aircraft, in particular those with jet engines where ash particles can be melted by the high operating temperature. Large eruptions can affect temperature as ash and droplets of sulfuric acid obscure the sun and cool the Earth's lower atmosphere or troposphere; however, they also absorb heat radiated up from the Earth, thereby warming the stratosphere.
    [Show full text]
  • Volcanic Landforms: the Landform Which Is Formed from the Material Thrown out to the Surface During Volcanic Activity Is Called Extrusive Landform
    Download Testbook App Volcanic Geography NCERT Notes Landforms For UPSC ABOUT VOLCANIC LANDFORM: Volcanic landform is categorised into two types they are:extrusive and intrusive landforms. This division is done based on whether magma cools within the crust or above the crust. By the cooling process of magma different types of rock are formed. Like: Plutonic rock, it is a rock which is magma within the crust whereas Igneous rock is formed by the cooling of lava above the surface. Along with that “igneous rock” term is also used to refer to all rocks of volcanic origin. Extrusive Volcanic Landforms: The landform which is formed from the material thrown out to the surface during volcanic activity is called extrusive landform. The materials which are thrown out during volcanic activity are: lava flows, pyroclastic debris, volcanic bombs, ash, dust and gases such as nitrogen compounds, sulphur compounds and minor amounts of chlorine, hydrogen and argon. Conical Vent and Fissure Vent: Conical Vent: It is a narrow cylindrical vent through which magma flows out violently. Such vents are commonly seen in andesitic volcanism. Fissure vent: Such vent is a narrow, linear through which lava erupts with any kind of explosive events. Such vents are usually seen in basaltic volcanism. Mid-Ocean Ridges: The volcanoes which are found in oceanic areas are called mid-ocean ridges. In them there is a system of mid-ocean ridges stretching for over 70000 km all through the ocean basins. And the central part of such a ridge usually gets frequent eruptions. Composite Type Volcanic Landforms: Such volcanic landforms are also called stratovolcanoes.
    [Show full text]
  • Magma Emplacement and Deformation in Rhyolitic Dykes: Insight Into Magmatic Outgassing
    MAGMA EMPLACEMENT AND DEFORMATION IN RHYOLITIC DYKES: INSIGHT INTO MAGMATIC OUTGASSING Presented for the degree of Ph.D. by Ellen Marie McGowan MGeol (The University of Leicester, 2011) Initial submission January 2016 Final submission September 2016 Lancaster Environment Centre, Lancaster University Declaration I, Ellen Marie McGowan, hereby declare that the content of this thesis is the result of my own work, and that no part of the work has been submitted in substantially the same form for the award of a higher degree elsewhere. This thesis is dedicated to Nan-Nar, who sadly passed away in 2015. Nan, you taught our family the importance and meaning of love, we love you. Abstract Exposed rhyolitic dykes at eroded volcanoes arguably provide in situ records of conduit processes during rhyolitic eruptions, thus bridging the gap between surface and sub-surface processes. This study involved micro- to macro-scale analysis of the textures and water content within shallow (emplacement depths <500 m) rhyolitic dykes at two Icelandic central volcanoes. It is demonstrated that dyke propagation commenced with the intrusion of gas- charged currents that were laden with particles, and that the distribution of intruded particles and degree of magmatic overpressure required for dyke propagation were governed by the country rock permeability and strength, with pre-existing fractures playing a pivotal governing role. During this stage of dyke evolution significant amounts of exsolved gas may have escaped. Furthermore, during later magma emplacement within the dyke interiors, particles that were intruded and deposited during the initial phase were sometimes preserved at the dyke margins, forming dyke- marginal external tuffisite veins, which would have been capable of facilitating persistent outgassing during dyke growth.
    [Show full text]