Volcanoes: a Field Guide to La Garrotxa Volcanic Zone Bibliography ISBN 9788439388524 I

Volcanoes A Field Guide to La Garrotxa Volcanic Zone

Generalitat de Catalunya Departament d’Agricultura, Ramaderia, Pesca, Alimentació i Medi Natural 0. Primeres pàgines-en 1/6/12 13:49 Página 1

Volcanoes A Field Guide to La Garrotxa Volcanic Zone 0. Primeres pàgines-en 1/6/12 13:49 Página 2

Biblioteca de Catalunya - Dades CIP Volcanoes: A Field Guide to La Garrotxa Volcanic Zone Bibliography ISBN 9788439388524 I. Martí i Molist, Joan, 1957- II. Catalunya. Departament d'Agricultura, Ramaderia, Pesca, Alimentació i Medi Natural III. Parc Natural de la Zona Volcànica de La Garrotxa (Catalunya) 1. Vulcanisme – Catalunya – Garrotxa 2. Parc Natural de la Zona Volcànica de La Garrotxa (Catalunya) – Guies 551.21(467.1 Gt)(036)

Published by Illustrations La Garrotxa Albert Martínez Volcanic Zone Figures 1, 2, 6-12, 15-17, 19-23, 25, 26, 38, 41, 42, Natural Park 44-50, 54, 56 and 57 Albert Pujadas Figures 3-5, 13, 14, 24, 51-53, 55, 68, 107, 108, 109, Legal deposit: B-11.374-2012 110, 111, 112, 113, and 115-117 ISBN 978-84-393-8852-4 Llorenç Planagumà Figures 81, 82, 84, 86, 94, 96, 99, 101, 103 and Original title: El vulcanisme Guia de 104 (Figures 82, 84, 86, 94, 96, 99, 101 and 104 have been modified according to the Vulcà Project camp de la Zona Volcànica de la geological base) Garrotxa (2000,2001) Montse Viñas Original drawings for figures 88-93 Title: Volcanoes A Field Guide to La Bibliographical references Garrotxa Volcanic Zone standardised and adapted by © La Garrotxa Volcanic Zone Montse Grabolosa Natural Park and authors With the support of the environmental © Traduccions i Tractament de la education organisations Documentació, SL La Cupp SCCL, Verd Volcànic and and Mike Lockwood Tosca Digital Version Natural Parc web page Printed by Ampans, Manresa 1st edition Olot, April 2012 Photographs Pep Callís Cover, figures 29, 34-37, 58-63, 66, 69, 73-76, 85, 87, 95, 97, 98, 100, 102, 105, 106 and 114 (deposited in La Garrotxa Volcanic Zone Natural Park Documentation Centre) Albert Pujadas Figures 28, 30, 33, 39, 40, 64, 66, 72, 78-80, 108, 110 and 113 Joan Martí Figures 15, 27 and 31 Emili Bassols Figure 32 La Garrotxa Volcanic Zone Natural Park Documentation Centre Figures 65, 67, 70 and 83 Maurice Krafft Figure 18 National Geographic Data Centre Figure 43 Llorenç Planagumà Figures 71, 77 and 102 0. Primeres pàgines-en 1/6/12 13:49 Página 3

Volcanoes A Field Guide to La Garrotxa Volcanic Zone

Joan Martí i Molist Jaume Almera Institute of Earth Sciences (CSIC), Barcelona Albert Pujadas Geodynamics Area Department of Environmental Sciences. University of Girona Dolors Ferrés Lopez Llorenç Planagumà Guàrdia Tosca. Collaborators with La Garrotxa Volcanic Zone Natural Park Josep Maria Mallarach Carrera Olot Foundation for Higher Education 0. Primeres pàgines-en 1/6/12 13:49 Página 4

Foreword

Just over 200 years ago, Francesc Xavier de Bolòs divul- ged the existence of the volcanoes in La Garrotxa to the scientific community for the first time. These volcanoes, whose eruptive activity had remodelled the landscape of Olot and its valleys, have had a remarkable influence over the centuries on local land-use and human activity. The extensive quarrying undertaken in part of the volcanic area from the 1960s to the 1980s provoked considerable social and scientific opposition, which eventually led to the passing of a law in 1982 declaring the volcanoes a protected area. The conservation of this natural heritage is justified by the fact that this is the youngest volcanic area in the Iberian Peninsula and one of the best preserved such areas in continental Europe. The geomorphological features found here include volcanic cones, lava flows, barrage lakes and basalt cliffs, and there are numerous sites where the geological processes that have generated so many different volcanic morphologies can be easily observed in great de- tail. Despite its legal protection, as part of the tasks implicit in the organization and consolidation of the Natural Park it was still necessary to halt the quarrying and to minimize and restore the region’s damaged geological heritage. A milestone was reached in 1995 with the restoration of the most emblematic volcano in the park, Croscat, not only the youngest volcano in the Iberian Peninsula, but also the one that has suffered most environmental impact. Nevertheless, more in-depth knowledge was required in the Park itself of the local volcanoes in order to build upon the studies undertaken early in the twentieth century and then reactivated in the 1960s. Initially, it was necessary to review all previous work and develop a project for a com- prehensive study of the geology of the Catalan volcanic region. The aim of this project, first contemplated in the early 1990s, was to study various geological and geophy- sical aspects of the Park as a means to learning more about the region’s geological heritage in general. Eventually, in 1993 a project began that, despite its narro- wer scope, was still very ambitious. It was financed entirely by the Department of the Environment through La Garrotxa Volcanic Zone Natural Park and executed by the Spanish National Research Council (CSIC) under the su- pervision of Dr Joan Martí, and would enable new geolo-

4 0. Primeres pàgines-en 1/6/12 13:49 Página 5

gists to be trained in the learning, management and rai- sing of awareness of the volcanoes of La Garrotxa. The results of this project are included in this guide, which in plain and simple terms provides new and valuable information for the study of the volcanoes of La Garrotxa. The publication of this guide is part of the Natural Park's management strategy, approved in 2000, which will enable us to improve our knowledge of volcanic activity in the region, plan research, preserve the Park’s geological and scenic values and increase awareness of the volcanic zone at local, national and international scales. I hope that this guide, which has been painstakingly pre- pared following strict criteria, helps to increase awareness of the value of this volcanic zone amongst teachers, university students and naturalists alike, thereby guarante- eing the knowledge, management and dissemination of a heritage that has been preserved for future generations.

Francesc Xavier Puig i Oliveras Director of La Garrotxa Volcanic Zone Natural Park

5 0. Primeres pàgines-en 1/6/12 13:49 Página 6

Contents

Introduction 8

l1l Volcanoes 11 l1l1l What is a volcano? 12 l1l2l Magma genesis 14 l1l2l1l Where is magma generated? 15 l1l3l Magma ascent 17 l1l3l1l How does magma ascend? 18 l1l3l2l What happens to magma during its ascent? 19 l1l4l Eruptive activity 22 l1l4l1l Why do eruptions occur? 23 l1l4l2l Types of eruptive activity 24 l1 l4l2l1 l Effusive activity 24 l1 l4l2l2l Explosive activity 24 l1l4l3l Volcanic materials 31 l1 l4l3l1 l Massive materials 31 l1 l4l3l2l Fragmentary materials 34 l1 l4l3l3l Types of pyroclastic deposit 35 l1l4l4l Volcanic morphology 39

l2l Volcanism in Catalonia 41 l2l1l Distribution and evolution of volcanoes 42 l2l2l The Catalan volcanic field 45 L'Empordà Volcanic Zone 46 La Selva Volcanic Zone 46 La Garrotxa Volcanic Zone 46 l2l3l Rocks and magma 49 l2l3l1 l Minerals 50 l2l3l2l Geochemical data 51 Magma genesis and ascent l2l4l Eruptions in La Garrotxa Volcanic Zone 53 l2l4l1 l Volcanoes and their phases of eruptive activity 54 l2l4l2l Eruptive activity and volcanic edifices 57 l2l5l Volcanic materials 58

6 0. Primeres pàgines-en 1/6/12 13:49 Página 7

l3l La Garrotxa Volcanic Zone. Sites of volcanic interest 61 1 l Castellfollit de la Roca: lava flows 64 2 l El Cairat: pyroclastic breccia 66 3 l Sant Joan les Fonts: massive materials 68 4 l Montsacopa: cone morphology 72 5 l Croscat: cinder cone 74 6 l Turó de la Pomereda: an eruption sequence 76 7 l Santa Margarida: pyroclastic deposits 78 8 l Can Tià: eruption sequence 80 9 l Els Arcs Valley: pyroclastic flow 82 10 l Location and morphology of the volcanic cones as seen 84 from Puig Rodó 11 l El Clot de l’Omera: maar 86 12 l Puig d'Adri: pyroclastic flow 88 13 l Puig d'Adri: pyroclastic surges 90 14 l The morphology of La Crosa de Sant Dalmai 92 15 l Pyroclastic surge and breccia of La Crosa de Sant Dalmai 94 Glossary 97 Bibliography 98 Map of La Garrotxa Volcanic Zone Natural Park Services 101 Environmental education organisations 102 Notes 104 Recommendations and indications for visitors 108

7 0. Primeres pàgines-en 1/6/12 13:49 Página 8

Introduction

This field guide presents a general but detailed view of the main features of La Garrotxa Volcanic Zone. It aims to be a useful tool for interpreting the landscape and geological processes in this volcanic zone and to provide the necessary tools for understanding from a geological perspective some of the most representative volcanic sites in the region. How significant is the presence of volcanoes in a region such as this? In which geodynamic period should they be placed? What is the origin and composition of volcanic rocks? What types of eruptions occurred? These are just some of the questions this field guide answers. Before offering an explanation of the volcanic history of La Garrotxa, this guide takes a look at general concepts of geology and volcanology that relate to the subject matter. Therefore, we first examine magma, how it is generated and reaches the surface, how its composition varies over time, the mechanisms that give rise to volcanic eruptions, and the main features of eruptions and their resulting structures. This book consists of three parts: 1. Volcanoes. An explanation of the general aspects and basic concepts of volcanism. 2. Volcanism in Catalonia. A brief description of the basic features of the most recent volcanic activity in the region. 3. Sites of volcanic interest. A description of 15 sites, the basis of a true field guide. The sites were selected according to the geological elements that can be observed and together exemplify the most remarkable features of the volcanoes found in Catalonia and, in particular, in La Garrotxa Volcanic Zone Natural Park. Accessibility was also a taken into account so that visits would be fairly simple. The selection of just 15 sites inevitably meant that others were omitted, many of which are also of great geological and educational interest, but far less accessible. This guide can be used on many levels: the text is accompanied by text boxes with a maroon background containing explanations of concepts of interest such as magma and the Earth's internal structure. The definition of terms written in italics can be found in the glossary.

8 0. Primeres pàgines-en 1/6/12 13:49 Página 9

Although the information given is presented in a relatively small space, we hope that the reading of this guide during a visit to the proposed sites will provide a general idea of why and how volcanoes occur in this region, still one of the least known geological features of Catalonia. The authors wish to thank the Catalan Cartographic Institute for the images and maps used in figures 54, 56, 57 and 81, and the Natural Sciences Section of the La Garrotxa Museum for the rock specimens appearing in the photographs.

9 0. Primeres pàgines-en 1/6/12 13:49 Página 10 1. Els volcans.en BAIXA 1/6/12 13:55 Página 11

Volcanoes 1. Elsvolcans.enBAIXA1/6/1213:55Página12

11 llElsVolcanoes volcans Figure 1. What isavolcano? Figure 2. l 1 l 1 Volcanic edifice Volcanic system Volcanic l eruption geological processes that involve the of series a of culmination the is morphology,rather final but its merely not is volcano a that clear it makes definition This morphological descriptions. imaginative somewhat to resort to have we cases many in and clear less becomes concept the terms, ‘scientific’ in idea this explain to try we when Yet, is. of volcano exact, a what less or more idea, of kind some has Everyone millions ofyears. even or thousands of hundreds for last that processes of result the actually are they years, of thousands to days few a just from time, of periods short relatively represent noes volca- scales time human and geological both on Although differing morphologies. • • • • • morphologies. differing of cones or shields to rise gives source point a around products these of accumulation The issue. material non-magmatic occasionally,and, Earth the within generated (magma) rock molten which through surface Earth's the in vent a is volcano A • • • of magma 12 (Figs. 1and2) . genesis, ascent and 11 llElsVolcanoes volcans molecule 2 Variation in the composition and physical SiO properties of magma Figure 3. Figure 4. 13 4 inter- basic . For this rea- than basic magma, , of up of , temperatures (over 63%) or (Fig. 3) viscous (Fig. 4). acid (between 52% and 63%). varies according to the silica content ) of the magma. Basic magma with a lower 2 • • • Magma is a mixture of molten, mainly silicate, rock that contains solid particles in suspension (crystals and rock fragments) and dissolved gases. • • • due to the larger number of bonds between its silica molecules: the greater the temperature, the molecular favours heating since viscosity, the lower excitation and makes it harder for bonds to form. higher reaches magma Basic to 1,100°C, 700–800°C. while acid magma melts at Density (SiO Physical properties the of three are temperature and viscosity Density, most significant physical properties of magma that determine the nature of the processes of as- the on mostly depends Density eruption. and cent chemical composition of the molten materials, whereas viscosity – resistance the to lava’s flow - also depends on the composition of the magma and its temperature anionic groups, isolated or bonded with others by metal cations The vast majority of the rocks we know of are made of minerals belonging to the silica family, that is, minerals consisting of SiO Magma silica content has a higher density due to the greater number of heavy metal cations it contains. Acid magma is more son, the magma resulting from the melting of these rocks Depending is on the percentage also of silica it mainly contains, magma is classed as either silicate. (less than 52%), mediate 1. Els volcans.en BAIXA 1/6/12 13:55 Página 13 Página 13:55 1/6/12 BAIXA volcans.en Els 1. 1. Elsvolcans.enBAIXA1/6/1213:55Página14

11 llElsVolcanoes volcans required tomelttherocks. are energy of amounts smallest the that here is it since minerals in contact zones betweens large a. Figure 6. remaining the as continues then and melt points melting lowest the with minerals the when gins be- genesis Magma pressure. given a at points sist of various minerals, each with different melting con- Rocks rock. the of part only affects Melting Partial melting Magma genesis e te siiain f ae b sm o te ieas that minerals make uptherocksignificantlylowersitsmeltingpoint. the of some by water of assimilation the re, However, in conditions of constant temperature and pressu- pressure. in fall great a undergoes pressure, and rature tempe- high very to subject initially rock, a if or temperature l 1 liquid state. • • • • • state. liquid a to solid a from change crust and mantle Earth's the in rocks the whereby process the is genesis Magma • • • h mlig rcs begins process melting The l 2 Partial melting process melting Partial l cend due to their buoyancy. as- to begin liquids the onwards, moment this from reached; is me volu- critical minimum a until areas certain in up build and channels interconnected small of network a form liquids These them. rround su- that minerals the than dense b. cnieal ices in increase considerable a a to subject is body rock solid if generated is Magma water increase intemperature combination: in or individually act may that reasons of number a for forms material Molten the surfaceinEarth’s crust. nearer generated be may it occasionally although upper mantle, the in generally Earth, the inside formed is Magma h lqis eeae ae less are generated liquids The (Fig. 5). 14 and onlyincertainproportions melt minerals some only time one any at since almost always speak of the partial melting of rocks we Thus, melt. to begin also rock the in minerals ween solidsandliquids. bet- separation effective increasingly an producing wards, down- compact solids residual melt zone. At the same time, the the of roof the near up and builds increases liquid of lume c. or Figure 5. Melting continues and the vo- greater presence of decompression, an Causes of rock melting rock of Causes (Fig. 6). 1 l Volcanoes Internal structure of the Earth Figure 8. 15 As well, we (Fig. 8). , just below the lithosphe- the below just , (Figs. 7 and 9). l Tectonic plates and the location of areas of volcanic activity 1 l asthenosphere , made up of the crust and the and crust the of up made , lithosphere 2 l the beha- in fragile is mantle, the of part outermost viour. the re, represents the upper part of the mantle, which is plastic in behaviour and can flow when subject to great forces. 1 In terms of the composition and density of its ma- its of density and composition the of terms In terials, the Earth's interior is divided into three layers: core, mantle and crust Figure 7. The internal of the Earth structure The The processes relating to magma formation can be explai- Volcanic tectonics. plate theory of the of context the in ned activity and in general magmatic activity is not randomly distributed over the Earth's surface, but is mostly concen- find we However, plates. tectonic of edges the along trated volcanoes in places other than plate edges, both on land and at sea, which tells us that melting at a local scale also place takes l generated? is magma Where can define two external layers in terms of the rigi- dity of the materials: a. b. The theory of plate tectonics proposes a dynamic a proposes tectonics plate theoryof The model of how the Earth works based on the fact that the lithosphere consists of a relatively small number of plates floating independently of each other on top of the asthenosphere. 1. Els volcans.en BAIXA 1/6/12 13:55 Página 15 Página 13:55 1/6/12 BAIXA volcans.en Els 1. 1. Elsvolcans.enBAIXA1/6/1213:55Página16

1 l Volcanoes ped considerably. drop- ambient has temperature the even melt though to the rocks of part enabling thereby minerals, the of point melting the wers subducted minerals,lo- of dehydration the by generated water, This mantle. the of system water enters the mineral when however, curs, oc- still Melting wered. lo- is temperature ter’s lat- the mantle, the into sinks lithosphere oler the other. When the co- under slides one de, colli- plates two When Subduction zones Plate boundaries Figure 9. Geodynamic environments ofvolcanism es plat tectonic between contact of Types lithosphere. Terrestrial of theridge. axis dorsal the towards continually rise then that rock solid of volumes huge of melting the and mantle the in material of decompression a to leads which apart, move plates lithospheric Two Oceanic ridges 16 Intraplate areas rm h core-mantle boundary. the from plume single a in rising convection a by caused mantle the in perature tem- the in increase lous anoma- an by nerated ge- are boundaries plate from far regions Volcanic Hotspots the ascentofmagma. favouring develop does faults normal of system a nevertheless, all; at occur not does or partial is lithosphere the in split the areas, some floor.In ocean new of mation for- the and lithosphere the of the rupture complete in culminate can that processes tensive dis- generates and crust the mantle of thinning a to leads the in vection In inner plate areas, con- Rift zones 1 l Volcanoes A magma chamber Figure 10. 17 , where it may solidify com- (Fig. 10) l 3 l • • • Magma ascent is the displacement of molten material from source areas to the surface and depends on the volume of liquid initially generated, its physical properties and the tectonic structure of the surrounding area. • • • 1 l Magma chambers These are reservoirs of molten rock that form within the lithosphere at depths of 1–60 kilometres, which are fed periodically by magma from melt zones. If they are connected to the Earth's surface, successive eruptions take place forming volcanoes or complex volcano- continuous necessarily not but - long a with es - periods of This activity. is the case of volca- and Vesuvius. Fuji, Etna noes such as Teide, re- for Earth the within halt may ascent Magma asons related to crust structure and the distribution of tectonic forces at each areas point. of magma In accumulation neutral density exists, that is, the density of the magma is equal to that of the surrounding rocks. In some cases magma rises to the Earth's surface almost rectly, di- without stopping, giving rise to individual, short-lived eruptions. Frequently, however, magma ac- cumulates in intermediate areas of the lithosphere in magma chambers Magma will break off from the melt zone and rise when the volume of molten material is sufficient to overcome by the surrounding rocks. the pressure exerted Magma ascent Magma pletely or continue to rise to the surface. 1. Els volcans.en BAIXA 1/6/12 13:55 Página 17 Página 13:55 1/6/12 BAIXA volcans.en Els 1. 1. Elsvolcans.enBAIXA1/6/1213:55Página18

1 l Volcanoes Ascent Figure 11. ie, hc te coe p gi oc the once again magma haspassedthrough. up close then which widen, to fractures causes material molten The surface. sure exerted by the magma as it rises towards the Ascent through dykes through dykes Ascent through dykes and diapiric ascent diapiric and dykes through Ascent occurs due to the pres- the to due occurs l dification givesrisetoplutonicigneousrocks. bodies of rock known as plutons. Their subsequent soli- forming crust the in up build material molten of masses surface, Earth's the reach often they Although tions. condi- structural favourable under occurs only and rare very is fractures narrow through magmas these of ment move- The diapirs. large as rise only can they mobility, position and consequently are more viscous. Given their com- in acidic more are crust the in generated Magmas that theycanmovethroughevennarrowfractures. means magmas basic fluid relatively these of mobility The fractures. through move they rocks, the of haviour be- fragile the to due where, areas, shallow into diapirs as rise initially mantle upper the in generated Magmas types: diapirsordykes(tensilefractures) two of are mechanisms ascent Magma rise. to magma cause rocks surrounding the and magma the between pressure in differences dense, less are liquids Since How doesmagmaascend? 1 l 3 l 1 l 18 temperature. high at magma the with contact on deform that mantle or crust lower the in rock ductile through Diapirs diapiric ascent are bodies of buoyant magma that push that magma buoyant of bodies are (Fig. 11) . 1 l Volcanoes Magma mixing Assimilation Fractional crystallisation Inserted rock Figure 12c. Figure 12a. Figure 12b. . . 19 (Fig. 12b) . . (Fig. 12c) l . 2 l 3 l 1 (Fig. 12a) Magma differentiates on its way to the surface, that is, of mechanisms principal Three changes. composition its magmatic differentiation occur during ascent: fractional country of assimilation and mixing magma crystallisation, rock. These processes take place simultaneously or individually and result in a broad range of chemical com- magmas. positions in the resulting Fractional crystallisation The pressure and temperature to which magma is sub- these Under upwards. moves it as drop generally jected new thermodynamic conditions, the various chemical elements in the magma regroup and form increasingly stable structures that give rise to the first solid These nuclei nuclei. grow to form crystals separate from the li- primary the from composition different a has which quid, magma. This process may be repeated several times during the evolutionary history of the magma. Thus, from an initial magma various different rocks (mineral aggregates) and residual liquids, all of different composition, may form l magma during happens to What its ascent? Magma mixing As it rises to the surface, magma may mix magmas of with different other composition and different physical properties. The end result will be magma with different characteristics from the initial magmas Assimilation In some cases, at higher temperatures, magma may partially melt the surrounding rock and assimilate part of its minerals, thereby again altering the original composition of the magma 1. Els volcans.en BAIXA 1/6/12 13:55 Página 19 Página 13:55 1/6/12 BAIXA volcans.en Els 1. 1. Elsvolcans.enBAIXA1/6/1213:55Página20

1 l Volcanoes Figure 14. a rhyolite a ring ascent. du- place took that processes differentiation chemical in the and magma the in occurring composition changes the reveals ppm) – million per parts in expressed and 0.1% than less (content elements trace and 0.1%) than greater proportion a in present (those ments ele- majority the between relationship The the magma fromwhichitwasformed. of evolution compositional and origin the to as information provide rock a in elements cal The content and proportion of the different chemi- The chemicalcompositionofigneousrocks melting partial of degrees of the existence area, source the in melt that rock of types different the place, takes melting where places and mechanisms melting of number small relatively the Despite What rocks cantellus Figure 13. Classification of volcanic rocks volcanic of Classification Minerological and chemical analysis of a basalt, a trachyte and trachyte a basalt, a of analysis chemical and Minerological 20 type ofrock. certain a into evolved it until evolution its and generated was magma primary how and where study geology of ches bran- two these analyses, textural and geoche- minerological chemical, on Based mistry. and petrology of disciplines the of basis the is rock of type certain a ses that have occurred in the formation of proces- petrogenetic the of Knowledge plement studiesofmagmaticdifferentiation. com- also and genesis, magma of chanisms small very quantities provide most information on the me- in appear that group earth rare the from elements and isotopes Radiogenic found ontheEarth'ssurface are that rocks igneous and volcanic of magmas is the origin of the great diversity formed. these of are solidification the Consequently, magmas of types ferent dif- of range wide a that ensure all tiation differen- magmatic of processes the and (Fig. 13) . 1 l Volcanoes (Fig. If magma reaches surface the and causes an eruption, it then begins to cool From this point onwards, very quickly. the diffusion of elements in the magma may completely be inhibited and If the magma is located at more superficial levels but still within the Earth's crust, it forms intrusive bodies such as dykes and sills. The process cooling is remarkably rapid and prevents new When magma solidifies deep down, the drop in temperature slow favours the diffusion chemical elements of and therefore the addition of new material to the crystals that are being for- . Texture analysis thus reveals the sta- . Texture give give rise to rocks such as obsidian and pumice with a vitreous texture but no crystals. Generally, however, the typical texture of the resultant rocks is microcrystalline (con- are rocks Some crystals). fine very of sisting charac- most feature a nature, in porphyritic rocks. sub-volcanic of teristic crystalline nuclei from growing. However, crystals developing deep down in more favourable conditions will be more regular in is shape and larger than the rest. The result a texture known as porphyritic, whereby (phenocrysts) crystals regular-shaped large, are surrounded by a crystalline, generally much finer grained matrix. crystallinea in results This med. a with rock granular texture containing large, similar- sized crystals. ges that the magma went through during its solidification. 15) The speed at which magma cools, determined by the depth at which it solidifies, is reflected in the texture of the rock 21 Emplacement of different types of igneous The texture of an igneous rock is defined by the characteristics of its mineralogical components (e.g. absolute and relative grain size, shape and mutual geometric relationships). Although some of these tex- field, the in observed be can aspects ture analysis almost always requires the microscope. use of a petrographic Types of igneous rock and their texture their and rock of igneous Types bodies Figure 15. 1. Els volcans.en BAIXA 1/6/12 13:55 Página 21 Página 13:55 1/6/12 BAIXA volcans.en Els 1. 1. Elsvolcans.enBAIXA1/6/1213:55Página22

1 l Volcanoes Eruptive activity Eruptive units l 1 from a point source. • • • • • source. point a from surface Earth's the onto gases and/or liquids materials, solid of emission the to related phenomena of series a involves activity Eruptive • • • l 4 Eruption Eruptive Eruptive Eruptive Eruptive epoch period phase pulse l rise tovolcanicfieldsorregions. give and years of millions or thousands last may period This place. take to faulting and folding as such phenomena tectonic for enough long time of periods by separated epochs, eruptive of succession A ces may form. edifi- volcanic various or one time which during years, of sands This unit covers several eruptions and may last hundreds or thou- nic erosionprocessestotakeplace. eruptions, enough time must elapse for soils to form or for non-volca- discrete as regarded be to are source point same the from eruptions two If deposits. of sequence a forms and phases or pulses peated The basic eruptive unit, lasting days, months or years that involves re- compaction. and granulometry, morphometry similar have deposits of series or sit depo- resulting The days. or hours lasting pulses eruptive of series A pulse gives risetoalayerorlevel. this during expelled material the of deposition The minutes. or seconds just for lasting materials volcanic emitting event short A eruptive period. and epoch eruptive eruption, phase, eruptive pulse, tive units from the least these to the most for important is as hierarchy follows: erup- established The surface. the onto rials mate- of exit the to related phenomena the of style and/or eruptive units can be differentiated according to the duration In the course of the formation of a volcanic region, up to five activity. eruptive the final stage of the volcanic process. is is this pacific, more sometimes violent, dynamics Sometimes the of internal manifestations obvious Earth's most the of One 22 1 l Volcanoes ) and sulphur dio- 2 A process of magma cooling and crystallisation takes place in the magma chambers. The residual liquid is volatile-rich, as volatiles often cannot be easily incorporated into crystalline structures. begin Bubbles to form that increase the pressure in the magma. O), carbon dioxide (CO 2 23 Gas expansion in a magma chamber. Figure 17. As the magma rises to pres- lithostatic lower the surface, it volatiles the that means sure contains separate from the liquid and form a separate gas phase. These volatiles form bubbles that increase in number and size. l Gas expansion in a 1 ). The solubility of these gases depends on the pressure and temperature of the magma. ). The solubility of these gases depends on the 2 l 4 l The supersaturation of gases (volatiles) in the magma the in (volatiles) gases of supersaturation The as it rises to the surface. The injection of new magma from deeper areas in the in areas deeper from magma new of injection The volcanic eruptions). Earth (the origin of most 1 volcanic conduit. Figure 16. Volatiles in magma Volatiles The most common volatiles in magmas are water vapour (H b. is pressure in increase the magma, basic volatile-poor In usually caused by the constant influx of new magma, whereas in acid magma it is due to a both. Therefore, combination in superficial reservoirs of of acid magma supersaturated in gas, the arrival of new magma can provoke an eruption. An eruption starts when the pressure exerted by the magma within the volcanic conduit or magma chamber mag- in increase This pressure. lithostatic the surpasses matic pressure may be due to two factors, which may or individually: operate simultaneously a. l occur? do eruptions Why xide (SO 1. Els volcans.en BAIXA 1/6/12 13:55 Página 23 Página 13:55 1/6/12 BAIXA volcans.en Els 1. 1. Elsvolcans.enBAIXA1/6/1213:55Página24

11 llElsVolcanoes volcans Figure 18. pyroclasts. • • • • • pyroclasts. called are fragments resulting The rocks. surrounding the of occasionally and magma of expulsion violent and fragmentation the by characterised is activity Explosive • • • • • • surface. the above emerged has it once magma to given name the lava, of emission continued and gentle the by characterised is activity Effusive • • • Emission of lava of Emission l rvos xlsv eutos n hc ms o the of most which in eruptions explosive • Previous es- gradual the to due magma acid of degassing • The initially magmas, ultrabasic and basic of emission • The This typeofactivityiscausedmostlyby: it intotheair. expel and magma the fragment to insufficient is conduit The pressure exerted by gas bubbles inside the volcanic ferent degreesofintensity. Strombolian, dif- have also types: eruptions Hydromagmatic explosiveness. following of degrees different to according Plinian, the and Vulcanian into classified are eruptions explosive eruptions, past in or volcanoes active in observed behaviour of type a basis a as Using around theconduittofragment. rocks the and increase to explosiveness the causing sions occur when magma enters into contact with water, explo- hydromagmatic Sometimes, lava. of fragments reach the surface causes a violent explosion that expels bubbles the as gas of release sudden The fragments. magma isolate and other each with interact bubbles These conduit. the of part final the in expand and bles bub- in concentrate gases explosion, the During mas. mag- volatile-rich with associated are eruptions Explosive l Volatile-poor magma leads to effusive eruptions l be identified. two types of eruptive activity, effusive and explosive, can Thus, released. finally is magma the which in place the in water of presence the by affected be also can type composition and its evolution during ascent. The activity initial its on therefore and magma the of content the volatile on mainly depend activity eruptive of features The Types oferuptiveactivity 1 1 1 gases inthemagmaarelostconduit. tions. erup- steam or fumaroles through volatiles of cape gas-poor.very l l l 4 4 4 l l 2 2 l 2 l l 1 2 l l l 24 Effusive activity Explosive activity (Fig. 18) . 1 l Volcanoes (Fig. 25 . The result is the expul- the is result The . (Fig. 16) (Fig. . Strombolian eruption . The volume of the ejecta does not normally exceed (Fig. 19) (Fig. sion of the magma fragments, which then build up around the vent having described ballistic trajectories through the air a cubic kilometre and the eruption column is less than the 20-km most high. distinguishing However, feature is the occurrence of a series of short-lived explosions lasting from minutes to a few hours. These explosions are The pressure of the gas reaching the surface and its ascent its and surface the reaching gas the of pressure The through the magma depend on the physical properties of the magma. This activity is generally associated with basaltic magmas with low viscosity in which bubbles rise to the surface fairly easily. activity Vulcanian This type of activity is named after another volcano, Vulcano, also in the Aeolian archipelago; its name is the Roman god of fire. taken from Vulcan, Vulcanian eruptions are highly explosive, but nevertheless smaller and less violent than Plinian eruptions Figure 19. Strombolian activity Strombolian Stromboli, a volcano in the Aeolian Islands off the eruption low-level of type a to name its lends Sicily, of coast north magma. gas mixed with escaping caused by Strombolian activity consists of discrete explosions sepa- se- to second a than less from range that periods by rated veral hours. Each of these explosions or pulses comes about as one or more bubbles of gas reach the rest at is magma the surface while 20) 1. Els volcans.en BAIXA 1/6/12 13:55 Página 25 Página 13:55 1/6/12 BAIXA volcans.en Els 1. 1. Elsvolcans.enBAIXA1/6/1213:55Página26

1 l Volcanoes Figure 20. Vulcanian eruption Vulcanian roclastic shower around the vent. When the gas content vent. At the same time, part the of the fragments fall in a py- from force sufficient with expelled be to ejecta continue the as long as for stable remains column The lumn thatmayreachheightsofover30kilometres. co- eruptive mushroom-shaped a form gases hot and pyroclasts second, per metres of hundreds Travelling eject huge volumes of fragments and volatiles and fragments of volumes huge eject and violent and explosive highly are eruptions Plinian tion ofMountVesuvius inAD79. the Pliny from erup- the of name description detailed a its wrote Younger,who takes activity of type This Plinian activity activity. vulcanian trigger and conduit the block that form domes occurs, this If volcano. the of neck the in solidify and up build often viscosities high their with magmas Andesitic the fragmentationofblockage. vaporised. Consequently, much of the ejecta result from matic gas or, more frequently, when an aquifer is partially mag- of amount the in increase an is there when either happens This broken. is blockage the enough strong is eruptions; if the pressure of the gases inside the conduit previous from debris by or magma consolidated and led coo- by rocks, by blocked is conduit the when caused 26 (Fig. 21) . 1 l Volcanoes • • • Hydromagmatic activity is the product of the interaction between magma or a source of magmatic heat and meteoric water, be it on the surface (seas, rivers or lakes) or groundwater (aquifers). • • • 27 . (Fig. 26) o por contacto directo Plinian eruption (Fig. 25) Figure 21. Hydromagmatic activity Hydromagmatic During a magmatic eruption, the entry of water into the system can completely alter the style of eruptive activity consequently an initially and gentle outflow of magma can sud- activity eruptive of type This violent. extremely become denly can occur with both basic magmas and more types. evolved The more specific term phreatomagmatism is used to describe the process of interaction groundwater. between In this magma case, the and transfer of conduc- energy either to due about come may from water the to magma the tion in the magma decreases, or if the radius of the vent in- speed the explosions, the during erosion to due creases at which the ejecta are released decreases and the partially or totally. collapses, either eruptive column Collapse of this type provoke pyroclastic flows that move cones at great speeds. of the volcanic down the sides This type of activity is generally associated with acid magmas, differentiated in magma chambers in which they have evolved and over a long period of time. become gas-enriched 1. Els volcans.en BAIXA 1/6/12 13:55 Página 27 Página 13:55 1/6/12 BAIXA volcans.en Els 1. 1. Elsvolcans.enBAIXA1/6/1213:55Página28

1 l Volcanoes tially dissolvedintheliquid. gas can separate and so it is par- more no continues, fermentation though even that, means sure pres- internal high This bottle. the of neck the in accumulating gas the by exerted force the of cause be- pressure high to subject is a. Figure 22. dissolved intheliquid. are gases volcanic the and sure pres- atmospheric than greater magma is subject to pressure far a. of bottle champagne a of opening the with process volcanic contrast to is occur eruptions tic magma- how understanding of way good A Magmatic eruptions The champagne in the bottle the in champagne The eoe h euto, the eruption, the Before Representation of a magmatic eruption magmatic a of Representation (Fig. 22) : that thengrowrapidly. from the liquid and form bubbles separate diffuse, to champagne the in dissolved gas the allows and significantly drops bottle the in pressure The released. is neck the in up built has that b. form bubbles. and expand gases the magma, the of decompression neous instanta- almost an is there ked, b. On popping the cork, the gas When the conduit is unbloc- is conduit the When 28 before. as out shoot to force the lacks it as bottle the of neck the of outside the down runs froth the escaped, has gas the all Once quid andforcingitoutindrops. li- the fragmenting speed, great at bottle the of neck the wards c. speeds. great reach can that lava of splashes of form the in conduit the of out it force and magma c. The gases drag the liquid to- liquid the drag gases The h gss rget the fragment gases The 1 l Volcanoes (Fig. , as has been shown in laboratory ex- periments. 24) lence of the hydromagmatic eruption hydromagmatic the of lence However, if you throw a However, whole bucket of water on the frying pan, the resulting reaction is very the case, latter this In above. the from different and oil the cools rapidly water of amount larger reduces the explosiveness of the interaction, which may become inexistent. This explains why underwater eruptions that occur in ridges on the for sea example, floor, are not excessi- vely violent. 29 . The resulting steam ex- Different types of volcanic deposits and edifices resulting from Simulation of a hydromagmatic eruption (Fig. 23) efficiency of the eruption. Wohletz and Sheridan (1983). ween the water interacting with the magma and the degree of explosivity or hydromagmatic activity whose nature is determined by the relationship bet- Figure 24. The relationship between the volume of water and magma that come into contact will go a long way to determining the vio- Figure 23. Just like the magma in an eruption, the hot oil which vaporises transfers its heat to the water, instantly Imagine a frying pan of hot oil on a acciden- water of drops kitchen few a which in stove tally land — the result is akin to a hydromagmatic explosion. Hydromagmatic eruptions Hydromagmatic pands, fragmenting the oil, which then spurts out of the pan at speed in the form of splas- a hes. The oil corresponds to the pyroclasts in volcanic eruption. 1. Els volcans.en BAIXA 1/6/12 13:55 Página 29 Página 13:55 1/6/12 BAIXA volcans.en Els 1. 1. Elsvolcans.enBAIXA1/6/1213:55Página30

1 l Volcanoes ay te vlaos i nw nw as known now Surtseyan activity. is volcanoes, other many of formation the in seen style, eruptive This instantly. vaporised was and conduit the red ente- seawater when caused eruption plosive land, was born. It was the result of a highly exis- volcanic new a Surtsey, Iceland of coast basic magmas. However, in 1963 off the south of emission the involves and Strombolian and effusive generally is Iceland in activity Eruptive Surtseyan activity the surface. to released being magma any without aquifer the forming rocks the of fragments the just expel that place take may explosions violent case, this In contact. direct into coming hout wit- conduction thermal by aquifer an vaporise and heat can material molten of intrusion An Figure 25. Phreatic activity Phreatic 30 the rockssurroundingconduititself. of and magma of fragments expel that occur explosions violent Then, aquifer. the in water the by exerted that than lower is conduit the the pressureofgasesinmagmainside if possible only is This vaporised. instantly be and magma the with contact direct into enter may groundwater eruption, an of course the In Figure 26. Figure 27. Phreatomagmatic activity Phreatomagmatic Eruption on Surtsey, Iceland Surtsey, on Eruption 1 l Volcanoes Solidified lava flow in • • • Volcanic materials consist of all the solid, liquid and gaseous products expelled during an eruption. We can distinguish between volatiles - gases that separate from the magma - and the materials that form deposits, classified as either massive or • • fragmentary. • the Teide volcanic complex Figure 28. 31 . These represent continuous represent These . (Fig. 28) . Massive materials l l 1 l 3 l (Fig. 29) 3 l 4 4 l l 1 1 These are compact bodies of homogeneous composition resulting from the cooling of lava flows from originating effusive eruptions. These rock bodies may be pre- of viscosity initial the on depending forms diverse in sent the magma. Variation in temperature during emplace- material ejected and the features of ment, the volume of irregularities slope, (e.g. deposited is it where terrain the affect the final form they take. and humidity) will also give and composition in basic are lavas fluid most The flows lava to rise The study of volcanic rocks helps understand the trans- portation and deposition mechanisms they originated from and therefore the type of eruptive activity involved. In the this geometric field and of textural study, relations of the built-up material and its composition have to be analysed. l l materials Volcanic outpourings of molten rocky material that slide along the flattest areas of land, potentially covering great distances. Lava from acid magma is very viscous and extre- In domes. of form normally the in vent the around up builds me cases this type of lava is practically solid emerges and leads to the formation of pinnacles. when it Lava flows morp- lithology, their by distinguished be can flows Lava hology and the features of the site. These parameters vary according to the composition of the liquid magma, their of features the and flow the of cooling of speed the emplacement. Lava flows can be classified by their external appearance into two large groups: smooth and rough. The internal structure can be massive and compacted, or fractured by joints. Internal of lava flows: retraction structure occu- it since cools it when considerably contracts Lava pies less volume in a solid than in a leads liquid to form. the This development inside the massive body of rock of various systems of fractures or cracks known as len- and columnar are jointing of types main The jointing. ticular 1. Els volcans.en BAIXA 1/6/12 13:55 Página 31 Página 13:55 1/6/12 BAIXA volcans.en Els 1. 1. Elsvolcans.enBAIXA1/6/1213:55Página32

1 l Volcanoes Figure 30. Figure 29. lenticular jointing lenticular Spheroidal weathering Spheroidal and Columnar minerals intherock. certain of weathering the by caused mottling, white is effect Another cracks. existing through infiltrates slowly the weathering of the volcanic rock caused as moisture of result the is lava of shells concentric of flaking This not really be thought of as a type of jointing of type a as of thought be really not can- flows, lava of parts outermost the in present often is that structure internal the weathering, Spheroidal columns. six-sided or five- into rock the split that joints prismatic forming fractures, vertical develop and lava the of base side the lava flow. These cells form perpendicular to the already cooled, causes convection cells to generate in- have flow,which the of bottom and top the and centre hot very the between temperature in difference The rest. at is flow lava the when occurs jointing Columnar the centreoflavaflow. in noticeable most is which fracturing, horizontal cilitate in the direction of flow. As the lava cools, the planes fa- planes parallel in deposit bubbles gas and vent, the by fed being still is flow the when instance for moving, is stream lava the when occurs jointing slab or Lenticular 32 (Fig. 30) . 1 l Volcanoes (Fig. Blister Rough lava ('a'a) . The outermost layer of the lava flow cools Figure 33. Figure 32. and forms a crust, which then breaks blocks as into the lava underneath continues to When the flow. fragments are large, this is called block lava. Submarine lava flows behave differently from sub-aerial flows. Upon coming into contact with the water, the lava cools suddenly and a fairly plastic layer of glass is formed creating blobs of lava. These blobs fall and roll down the slope on top of each other and become misshapen, thereby forming what is known as pillow lava. 32) Viscous lavas have a rough, irregular surface made up of broken lava blocks or clinker 33 . . In some cases, some In . (Fig. 33) (figura 31) Smooth lava (pahoehoe) Figure 31. A single lava flow may exhibit diverse types of morphology. Thus, we frequently observe a lava flow with an initial stretch with a smooth surface, then an area of ropy lava that becomes increasingly followed irregular, by an area of rough lava. Blisters When the lava flow flows over a lake or a we- tland, the water vaporises and a huge amount of gas is incorporated into the Gas flow. bubbles rise inside the flow towards the surface, which is often semi-solid due to more rapid cooling. The build-up of bubbles in this area causes pressure that can deform and even break the surface of the lava flow. The result are mounds, dozens of metres high known as blisters (tossols in Catalan) Very Very fluid lavas usually have a very smooth or surface undulating Lava flow morphology Lava due to slight turbulence inside the flow, the surface may wrinkle or fold perpendicular to giving rise to rope lava. the direction of flow, 1. Els volcans.en BAIXA 1/6/12 13:55 Página 33 Página 13:55 1/6/12 BAIXA volcans.en Els 1. 1. Elsvolcans.enBAIXA1/6/1213:55Página34

1 l Volcanoes the surface. reaching magma from directly derive fragments, Juvenile fragments: ment, whileothersconsistofamixthetwo. roclastic deposits consist of only one type of frag- py- Some nature. their to according tinguishable Different types of clasts - juvenile or lithic - are dis- Nature offragments Figure 34. blocks and lapilli ash, groups: main three into size by classified be can Pyroclasts sizes. of variety a in fragments to rise give Volcanicexplosions Classification bysize lar features. particu- own their have and deposits roclastic py- the of part form small, or large fragments, and (fire) pyro, Greek the from comes pyroclast word The Pyroclasts Blocks (Fig. 34) Classification of pyroclasts by size by pyroclasts of Classification klastos . also known as essential as known also boe) Ec o the of Each (broken). activity. eruptive of type the of understanding the to damental ved from close up, the study of pyroclastic ejecta is fun- obser- be cannot it that violent so is eruption an When deposits). forming pyroclasts(fragmentary deposited are materials these all Finally, clasts. matic mag- the with mix fragments resulting the and wall ney chim- or vent the of part break can explosions volcanic cases, some violently.In expelled are which magma, of generated blobs form bubbles Gas clasts eruptions. explosive by mainly of consist materials Fragmentary l 1 l 4 64 mm Lapilli l 3 l 2 l 34 Fragmentary materials ous rocks that form part of the volcanic substrate. igne- or metamorphic sedimentary, of fragments are they when accidental, or eruptions, previous from rocks from derive they when accessory, be can fragments Lithic eruption. the during plosions rocks forming the vent that were ripped out by ex- Lithic fragments: mm. 64 over measure blocks and mm, 2–64 are lapilli mm; 2 than less of diameter a has Ash these are fragments of the of fragments are these 2 mm Ash 1 l Volcanoes Volcanic bomb Scoria Pumice Figure 36. Figure 37. Figure 35. 35 . Fall deposits may deposits Fall . . (Fig. 38) (Fig. (Fig. 37) . 3 . . (Fig. 35) when when fragments of (Fig. 36) Types of pyroclastic deposit of pyroclastic Types juvenile juvenile fragments, generally lapilli- l juvenile pyroclasts, lapilli-sized or lar- 3 l 3 l 4 l 1 Pumice: sized, acid in composition and pale-coloured. Pumice floats since it is highly porous and its density does not exceed 1g/cm l Fragmentary materials build up different types of depo- transport formation, of mechanisms the to according sits basic three distinguish can We operation. in deposit and pyroclastic and surge pyroclastic fall, pyroclastic - types flow deposits – that occur due to differences in the genesis of the deposit. fall deposits Pyroclastic These are formed when ejecta from an eruption either fall freely and vertically having formed part of the erup- ejected being after trajectory ballistic a on or column tion volcano the of crater the from Other terminology used used terminology Other bombs: Volcanic magma the size of lapilli or blocks that are not completely cooled when ejected, move through the air they are modified into rounded or spindle-shaped forms. If they have bread-crust called are they cracks superficial bombs. These are formed by the expansion of gas bubbles inside the still semi-molten bomb when the surface has already cooled and is easily fractured show gradation in size and laterally continuous parallel banding. The further they land from the vent, the thinner the deposit and the smaller the fragments. Scoria: of ger, irregular morphology that contain many basaltic are fragments These vesicles. or holes or basaltic-andesitic in composition and may be semi-welded in deposits close to the vent because they were not completely solid when they were deposited 1. Els volcans.en BAIXA 1/6/12 13:55 Página 35 Página 13:55 1/6/12 BAIXA volcans.en Els 1. 1. Elsvolcans.enBAIXA1/6/1213:55Página36

1 l Volcanoes ihc rget, s nw a pyroclastic as breccia known is fragments, lithic of presence considerable a includes which build-up, resulting the and component cal verti- the than important more much is cases these in component horizontal the eruptions, Strombolian in Unlike trajectories. ballistic follows ejecta the of part water, of poration eva- instantaneous the by caused plosions c. Hydrovolcanic deposits: on higherground and depressions in both up build and land evenly the cover deposits These pyroclasts. the of emplacement the affect and column the up make that materials of cloud the displace can winds Prevailing pyroclasts. of shower a eruption columns. Finally, Plinian these materials fall in characteristic forming heights rable conside- to rise low,fragments is density their b. Plinian pyroclastic deposits: cone. volcanic a form and vent the around up build fragments which in eruptions, Strombolian of characteristic is mechanism This trajectory. great reach not do ballistic a on directly ground to fall and heights ejecta the that mean fragments the of density high and eruption the a. Strombolian falldeposits: Types offalldeposit Figure 38. (Fig. 40) posit de fall a of emplacement and pyroclasts of projection Ballistic . (Fig. 39) . the low energy of in violent ex- when 36 Figure 39. Figure 40. Pyroclastic breccia Pyroclastic Plinian fall deposit fall Plinian 1 l Volcanoes . (Fig. (Fig. 42) 37 Emission and emplacement of a pyroclastic surge . Such deposits are characterised by unidirectional annular explosions at ground level produced directly radially. in the vent that move the collapse of the outside of the column, which than the centre; diluted and colder much more is The build-up of the materials transported by these flows fills valleys and depressions. They normally have no clear stratification or any defined internal structure and are often compacted by secondary cementation. They are typical of explosive eruptions associated with differentiated magma, although they can also occur in basic volcanism. Large pumice-rich pyroclastic flows known as ignimbrites. are Figure 41. Pyroclastic surge deposits surge Pyroclastic These deposits originate in turbulent gaseous flows that transport horizontally small amounts of pyroclasts at su- personic speeds, close to the ground. The formation of mainly with: surges is associated pyroclastic a. b. These are high-energy flows and can move up slopes. Consequently, the deposits left by pyroclastic surges cover the although underlying the topography, most im- bottoms valley in occurs material of build-up portant Pyroclastic flow deposits Pyroclastic These consist of fast-moving laminar flows of gas and la- spread they as depressions in fill that fragments rock terally. Generally, they originate after the total or partial empla- during and column eruption vertical a of collapse cloud cement are accompanied by a huge ash sedimentary structures and good granulometric classifi- ma- the on lying base erosive an have often They cation. terials of the substrate. 41) 1. Els volcans.en BAIXA 1/6/12 13:55 Página 37 Página 13:55 1/6/12 BAIXA volcans.en Els 1. 1. Elsvolcans.enBAIXA1/6/1213:55Página38

1 l Volcanoes Figure 42. Figure 43. Pyroclastic flow deposit flow Pyroclastic Lahar emplacement Lahar eruption - however small - can cause huge slides of mud and mud of slides huge cause can - small however - eruption of snow cover volcanoes or when their craters contain lakes, an mudflow.a quantities or large debris When volcanic of flow ted Lahar Lahars diate formscanbefoundbetweentheseextremes. rent types of emplacements and flows and many interme- diffe- of range wide a of manifestations extreme are ges sur- and flows pyroclastic from originating deposits The is an Indonesian word used to describe a water-satura- a describe to used word Indonesian an is 38 materials sedimentary with terspersed in- rock) pyroclastic or deposits (lavas volcanic find we materials of sequence the In picked upalongthe way. material other and rock nic volca- of masses chaotic are deposits Lahar villages. tire en- even and vehicles to res, infrastructu- and vegetation away from paths, sweep their in everything and banks their break to rivers and cause speeds high at travel flows These rock. volcanic (Fig. 43) . 1 l Volcanoes Maar Cinder cone Tuff cone Tuff ring Figure 47. Figure 44. Figure 45. Figure 46. 39 l 4 l 4 l 1 The build-up of volcanic materials ejected close to the vent gives rise to the formation of one or several volcanic edifices that are generally cone-shaped and variable clo- is constructions volcanic of morphology The size. in episo- the and activity eruptive of type the to related sely des that have taken place during the history of the volcano. Hence, we can classify volcanoes as either monogenetic or polygenetic. Monogenetic volcanoes These volcanoes are formed in the course of a eruption, single which can have several phases and pulses. The edifice constructed is simple and the main features include pyroclastic cones, tuff cones, tuff re- rings can phases eruptive different and of succession A maars. edi- of types these of several of superposition the in sult fices in a single volcano. cones Pyroclastic or cinder They are the result of a Strombolian eruption and built mostly from cinder (scoria). The craters may be cir- are cular or breached on one side. The horseshoe shape may be due to the inclination of the vent, the presence of prevailing winds that whip pyroclasts along in a given direction, or to the expulsion of lavas that drag a part of flanks The them. with along of deposits pyroclastic the cinder cone slope at an angle of 30–40°. cones Tuff These are formed from the interaction of magma for- materials The eruption. hydrovolcanic and a during water med are mostly compact pyroclastic surges and flows. Craters are small and the flanks of the cone 20–25°. slope at rings Tuff These form as a result of a phreatomagmatic eruption. They consist of pyroclastic breccia, surges and sloping flanks flows. with rim low a and craters large have They at around 10°. Maars These form as a result of a phreatomagmatic eruption and are similar to tuff rings. In this case, the crater lies below the surrounding topography and the cone, for- veryis deposits, flow low. and surge pyroclastic by med l morphology Volcanic 1. Els volcans.en BAIXA 1/6/12 13:55 Página 39 Página 13:55 1/6/12 BAIXA volcans.en Els 1. 1. Elsvolcans.enBAIXA1/6/1213:55Página40

1 l Volcanoes ihy xlsv pae (hs b. h end The b). (phase phases explosive highly more generates and volcano the reactivates cause the chamber to collapse. This collapse can magma the of emptying total or partial The a). (phase of rapidly ejected quantities are magma large eruption an of course the in chambers, magma with volcanoes In Collapse calderas Figure 50. Figure 49. Figure 48. Formation of a collapse caldera caldera collapse a of Formation Shield volcano Shield Stratovolcano parasite cones. to the activity of the main edifice, known as adventive or linked clearly them, around edifices secondary smaller Both monogenetic and polygenetic volcanoes may have kilometres indiameter. than less of angles 10°, but in some at cases the base may are be over a hundred slope the of flanks the high and very not are cone The shield. a resembles plies, im- name its as and, shape in concave is flows, lava of accumulation the by formed edifice, The predominates. activity effusive which in eruptions basaltic from Formed Shield volcanoes have flanks withslopesofover40°. may large, is which edifice, The flows. lava and deposits fragmentary of layers several by formed are they Consequently, alternates. activity effusive and ve explosi- where eruptions magma acid intermediate with associated are they volcanoes, composite called Also Stratovolcanoes stratovolcanoes andshieldvolcanoes. as known are edifices resulting The evolve. can magmas primary the where and place taken have refilling and emptying of episodes successive where chambers magma near-surface or intermediate with associated often are They years. of millions to thousands from riod, These are formed from several eruptions over a long pe- Polygenetic volcanoes 40 ejected inphaseb. deposits ignimbrite of mostly made and tical internal walls that limit the depression are ver- wide, kilometres The c). (phase calderas collapse depression, a as known a is result 2. El vulcanisme a Catalunya-en baixa 4/6/12 07:09 Página 41

Volcanism in Catalonia 2. ElvulcanismeaCatalunya-enbaixa4/6/1207:09Página42

2 l Volcanism in Catalonia compressive tectonic conditions tectonic compressive by characterised is and Ma) the (24–18 during Miocene occurred period eruptive first The of volcanoes Distribution andevolution l and Sardinia. Corsica of west to Islands Balearic the from SW sloping towards the Iberian Peninsula running NE- plane subduction a of presence the by explained is eruptions these of origin The Peninsula. Iberian the and Islands Balearic the between situated features submarine by all, above and, Mallorca in manifestations volcanic sub-aerial by represented mostly calc-alkaline, was magmatism associated Figure 51. riod. Calc-alkaline volcanism Calc-alkaline riod. 2 l 1 Western Mediterranean. Compression pe- Compression Mediterranean. Western l (Fig. 51) and distensivestructures. compressive of overlap the given complex is gion the of northeast the Iberian in Peninsula. The geological history of the re- exists both of dence evi- and Mediterranean, western the in identified been have periods eruptive two rocks, volcanic of dating and composition the basis a as Using much ofWestern Europe. affects that context geodynamic broader a within lies field volcanic Catalan the constitute that rocks and morphologies volcanic of series the of origin The event. sporadic a simply not were Quaternary and Neogene the during general in Catalunya in and GarrotxaeruptiveLaTheepisodes placein tookthat . The . 42 today find we that distension of one to changed tion situa- the onwards, Miocene Upper the From for example,offthecoastofTarragona. occurring, episodes volcanic isolated during formed were volcanoes submarine of number a that mentioning worth also is It fields. nic volca- Catalan and Columbrets Els Valencian, the of manifestations magmatic alkaline the with associated and Europe Western affecting rift intraplate an of development the to ponds Alkaline volcanism Alkaline Figure 52. (Fig. 52) Western Mediterranean. Distension period. Distension Mediterranean. Western Ti scn cce corres- cycle second This . 2 l Volcanism in Catalonia number of large normal mostly NE-SW. faults running The magma has taken advantage of these the to rise to lithosphere the in weaknesses surface and there are thus numerous volcanic manifestations in both Eastern and Western Europe associated with this rift system. The most important such volcanic fields ones Catalonia. Auvergne (France) and are in Eiffel (Germany), 43 . Within this rift there is there rift this Within . (figura 53) (figura The intracontinental rift system in Western Europe Figure 53. During the Upper Miocene at the end of the Tertiary Period, an extensive process Eurasian the of sector western the in began As active. be to considered still is that Plate a result of the distensive forces operating measu- structure rift-type a plate, the within ring over 2,000 km from the North Sea has Peninsula Iberian southern the to coast developed The European Cenozoic Rift System Cenozoic European The a series of troughs and raised blocks that have been created by the movement of a 2. El vulcanisme a Catalunya-en baixa 4/6/12 07:09 Página 43 Página 07:09 4/6/12 baixa Catalunya-en a vulcanisme El 2. 2. ElvulcanismeaCatalunya-enbaixa4/6/1207:09Página44

2 l Volcanism in Catalonia are foundonorclosetooneofthesefaults. Most of the volcanoes in northeast Catalonia Olot the Trough). and Serralada depression Selva La La and of mountains Transversal) and sunkenblocks(L'Empordà the and Guilleries Les Gavarres, (Les blocks raised of series a separate which and faults, Vilopriu Riurà Juià, Camós-Celrà, Cartellà, Llorà, Amer, the as known are fractures Figure 54. (Figs. 53and54) rift the within those to perpendicular lie that faults normal of series a by displaced been have Peninsula Iberian the of northeast the La and rivers, in situated segments two TechThese Cerdanya. and Têt the Lion, of Gulf the of trenches fault Troughthe and Valencia the as such structures discrete of series a contains system rift European The ts ts faul with trough tectonic a of part of cross-section Geological . From west to east, these east, to west From 44 2 l Volcanism in Catalonia 45 . (Fig. 55) l Map of NE Catalonia and geological table (modified from Saula et al.) 2 l 2 The combination of the age of the volcanic phenomena in and La Selva and the the L’Empordà effects of erosive processes explain why the volcanic edifices of these zones have all but disappeared, and also why only two the har- dest massive materials including fragments of lava flows are still recognizable. and collapsed chimneys The series of Neogene-Quaternary eruptive rocks in northeast Catalonia are from deduce can We Garrotxa. La and Selva La L'Empordà, situated in three the and features eruptive the of distribution geographical the volcanic areas: geochronological data available that the magmatic activity began in the L’Empordà, moved south towards La Selva La Garrotxa and then finally reached Figure 55. l field volcanic Catalan The 2. El vulcanisme a Catalunya-en baixa 4/6/12 07:09 Página 45 Página 07:09 4/6/12 baixa Catalunya-en a vulcanisme El 2. 2. ElvulcanismeaCatalunya-enbaixa4/6/1207:09Página46

2 l Volcanism in Catalonia and five in the Llémena ValleyLlémena the in five and Natural Park,withafurthertwointheHostolesValley Zone Volcanic Garrotxa La in identified been have volcanoes in Thirty-eight Garrotxa. La volcanoes in are Catalonia best-preserved and youngest The La Garrotxa Volcanic Zone erupted inmoremoderntimes. that volcano well-preserved a is depression La Selva of rim northern the on Dalmai Sant de Crosa La at 5–20 Ma. rocks these dated have analyses Geochronological dromagmatic eruptions can be identified. deposits of fragmentary materials originating from hy- parts, some In jointing. columnar marked exhibit and Corneli and Hostalric are its most interesting features Sant of chimneys collapsed The Riudarenes. and Selva la de Maçanet around mostly outcrops, basalt fifty around of series a comprises also region This La SelvaVolcanic Zone rentiation. from the cooling of magma that had undergone diffe- resulted have rocks volcanic evolved more These Empordà). (L'Alt d'Empordà Arenys and Vilacolum at outcrops trachyte the are noteworthy Particularly oldest being around 14 Ma. the by with Ma, 6 over from date and deposits covered Pliocene are materials volcanic these of Most d'Empordà. Arenys and Rupià La d'Empordà, around Bisbal located are important most the of which Empordà, Baix El and L'Alt of regions the ween bet- shared outcrops, trachyte of number a as well as outcrops, basalt fifty around contains zone This L'Empordà Volcanic Zone years. 15,000 every approximately occurred has episode eruptive an that suggest estimates current and old years 350,000–10,000 at zone volcanic this tuates si- data geochronological available Quaternary, the to prior activity volcanic of evidence some Despite ble (of particular interest in the Llémena Valley). (both visita- are origin) deposits in hydromagmatic and pyroclastic Strombolian and flows lava of ber 46 (Fig. 56) . A large num- large A 2 l Volcanism in Catalonia Pla sa Ribera Sant Jordi Racó Fontpobra Can Tià Sant Marc Puig Roig Traiter Les Medes Tuta de Colltort 31 32 33 34 35 36 37 38 39 40 Cabrioler Puig Jordà Puig de Mar Comadega Puig Subia Roca negra Simon Puig de la CostaPuig de Martinyà Santa Margarida 21 22 23 24 25 26 27 28 29 30 47 the Garrinada Montsacopa Montolivet Can Barraca Puig Astrol Pujalós Croscat Bac de les Tries Puig de la Garsa Les Bisaroques 13 14 15 16 17 18 19 20 11 12 Location of the volcanoes in La Garrotxa Volcanic Zone Gengí La Canya Aiguanegra Repas Repassot Cairat Claperols Puig de l'Ós Puig de l'EstanyPuig de Bellaire 8 9 1 2 3 4 5 6 7 10 Figure 56. 2. El vulcanisme a Catalunya-en baixa 4/6/12 07:09 Página 47 Página 07:09 4/6/12 baixa Catalunya-en a vulcanisme El 2. 2. ElvulcanismeaCatalunya-enbaixa4/6/1207:09Página48

2 l Volcanism in Catalonia Figure 57. 7 6 5 4 3 2 1 Puig Montner Montner Puig Rocacorba de Boc del Granollers Banya la de Puig l’Omera de Clot Rocàs El d’Adri Dalmai Puig Sant de Crosa pression de Selva La and Valley Llémena the in volcanoes the of Location 48 2 l Volcanism in Catalonia Sample from Vilacolum crystals). Figure 59. The paler trachyte is porphyritic in texture (feldspar 49 l Sample from Olot 3 l 2 vesicular, is very dense. Figure 58. Basalt is a grey-black rock that, when not particularly The composition of the rocks that make general up in field volcanic Catalan the and the Garrotxa La of zone volcanic is relatively uniform. With the exception of the trachyte out- Empordà, all volcanic materials are composed crops in L’Alt of basalt and basanite, low in silica and high in sodium and potassium. Therefore, as a whole the volcanic materials in of result the are They alkaline. as classified be can Catalonia the cooling of rapidly ascending basalt magmas and are volcanic zones. characteristic of intraplate l magma and Rocks 2. El vulcanisme a Catalunya-en baixa 4/6/12 07:09 Página 49 Página 07:09 4/6/12 baixa Catalunya-en a vulcanisme El 2. 2. ElvulcanismeaCatalunya-enbaixa4/6/1207:09Página50

2 l Volcanism in Catalonia A pale green mineral with a glassy a with mineral green pale A Figure 60. Observable minerals lustre. It appears both in the form of form the in both appears It lustre. phenocrysts and as part of the the of part as and phenocrysts matrix. Large crystals tend to be to tend crystals Large matrix. idiomorphic with regular sides sides regular with idiomorphic corresponding to the facets of the of facets the to corresponding crystal. Olivine Olivine l and ironoxides. titanium as well as crystals, sanidine elongated small, numerous contains matrix trachyte the microscope, the with some pyroxene and biotite. Under gioclase crystals silicon oxide(over60%)andarecomposedoflargepla- Unlike basalt rocks, trachytes have a high percentage of Dark with green tones. Pyroxenes tones. green with Dark Figure 61. silicon dioxide of percentage the in reduction slight a by rally gene- and leucite as such crystals feldspathoid small of presence the by characterised are They eye. naked the with distinguish to hard very are exist that basanite and basalt between differences mineralogical few very The in smallquantities. present also are analcime and leucite as such minerals which is often rich in iron oxide (mainly magnetite). Other matrix, vitreous partially or microcrystalline a in nocrysts phe- feldspar plagioclase and are pyroxene - olivine, microscope small a under only and – visible is that all cases, most In simple. and uniform is mineralogy Basalt Minerals are found both as phenocrysts and phenocrysts as both found are in the matrix. Most are titaniferous are Most matrix. the in augites and are often present in present often are and augites idiomorphic or sub-idiomorphic or idiomorphic forms. 2 l 3 l 1 (Fig. 13) Pyroxene l 50 . A white mineral. This type of of type This mineral. white A Figure 62. feldspar is generally subordinate in subordinate generally is feldspar the matrix and is only found found only is and matrix the exceptionally as a phenocryst.. a as exceptionally Plagioclase 2 l Volcanism in Catalonia 51 l 2 l 3 l 2 The The geochemistry of the basalt rocks in the Catalan volcanic field displays considerable homogeneity in major elements, including silicon, aluminium, iron and calcium oxides. The only significant variations are in the percentage of titanium oxide, attributable to variable temperatures in the magma when rocks were being formed. the Nevertheless, important variations exist between dif- elements trace of amount the of terms in rocks ferent (nickel, cobalt, chromium and strontium) and rare earth elements (lanthanum, cerium and neodymium) they contain. This variation in chemical composition coincides well with the three geographic regions - L’Empordà, La Selva and La Garrotxa - and reveals area. source magma the in differences Variations observed in the geochemical analysis of the basalt rocks enable us to understand better the genesis and ascent of the magmas that gave rise to are areas source magma The Catalonia. in volcanism generally situated in the asthenospheric mantle, although the magmas that generated the volcanic features in L’Empordà come from an area that is more lithospheric. The presence of these two source areas, the aste- nosphere and the lower lithosphere, can be linked to the evolution of the European rift system. During the initial extensive stages, the thinning of the lithosphere led to its decompression and partial melting. The crust was still thick and pockets of magmas were trapped in small chambers in which the Empordà trachytes differentiated and formed. As the rift pro- gressed and the lithosphere the grew asthe- thinner, nosphere ascended and permitted less evolved mol- rise. to materials ten contamination of lack total almost the cases, some In scant their and crust the from rocks by basalts the of differentiation indicate that the ascent of the magma pockets to the surface was rapid. from the source l data Geochemical ascent genesis and Magma 2. El vulcanisme a Catalunya-en baixa 4/6/12 07:09 Página 51 Página 07:09 4/6/12 baixa Catalunya-en a vulcanisme El 2. 2. ElvulcanismeaCatalunya-enbaixa4/6/1207:09Página52

2 l Volcanism in Catalonia Enclaves Figure 63. occur also may rocks sedimentary or metamorphic some although rocks, plutonic of mostly sist con- xenoliths, or enclaves as frag- known These ments, ascent. its during magma the by captured were that rock of fragments tain Some lava flows and pyroclastic deposits con- this termissomewhatofamisnomer. origin, explosive their given although, claves’, ‘en- to referred also are deposits pyroclastic in found fragments lithic the cases, some In before engulfed transporting themtothesurface. then and wall vent the of out tore magma the that mantle) the in cases some in (or lithosphere the in formed length) in centimetres few a (usually blocks of sist (Fig. 63) Enclave of plutonic rock: granitoid rock: plutonic of Enclave . These enclaves usually con- usually enclaves These . 52 pension. sus- in enclaves the maintain to necessary ascent an been have that would m/s 0.2 around of speed show magma in ments frag- these of floatability the of Calculations were immersed and dragged to the surface. ascent, magma’s the of speed the to due but, liquid, basaltic the than xenoliths denser were These volcanoes). d'Adri Puig and Boc de Banya la de Puig Rocanegra, (e.g. crust lower the in basalts the in tiation differen- magma of remains from or mantle trabasic xenoliths ul- of presence the is interest great of Also Figure 64. Ultrabasic enclave: dunite enclave: Ultrabasic (Fig. 64) derived from the from derived 2 l Volcanism in Catalonia 53 l 4 l 2 Each of the volcanoes in the La Garrotxa during was a single formed eruption. Thus, they are monogenetic in nature and were created by the ejection of a pocket of magma whose exhaustion marked the end of the volcanic activity. However, the various phases of activity present chan- a during by marked are they since visible are eruption the alt- exterior, the to journey magma's the of style the in ge hough the time-lapse between each of these phases development soil or stages erosive for sufficient not was to begin. l Garrotxa in La Eruptions Zone Volcanic 2. El vulcanisme a Catalunya-en baixa 4/6/12 07:09 Página 53 Página 07:09 4/6/12 baixa Catalunya-en a vulcanisme El 2. 2. ElvulcanismeaCatalunya-enbaixa4/6/1207:09Página54

2 l Volcanism in Catalonia Figure 65. Fageda d’en Jordà d’en Fageda h stands the famous beechwood of La of beechwood famous the stands h whic on flow, lava and crater horseshoe-shaped its with Croscat l l’Omera). Astrol; (Puig Strombolian either phase, eruptive single a More rarely, we find volcanoes that were formed from (Fig. 66) activity as the magma loses its gas with effusive into evolves activity,then Strombolian which starts process evolutionary oft-repeated An phreatomagmatic eruptive phases. and Strombolian effusive, identified has deposits nic volca- these of study The features. volcanic different monotonous the composition of the magma, has left a legacy of many despite that, phases magmatic purely and hydromagmatic combined Garrotxa La in volcanoes the to rise gave that activity eruptive The eruptive activity Volcanoes andtheirphasesof volcanoes of El Traiter, La Garrinada and Puig d’Adri Puig Traiter,and El Garrinada of La volcanoes the of case the is this activity; effusive finally, and, Strombolian into develops then which activity, matic phreatomag- with starts eruption the cases, other In of volcanoes the Croscat, MontolivetandSantMarc. are evolution this of examples 2 l 4 l 1 . Fig. 67) l 54 o praoamtc E Co de Clot (El phreatomagmatic or , (Fig. 65) . The best 2 l Volcanism in Catalonia 55 Puig Astrol volcanoe Puig d’Adri volcanoe Eruptions in which the initial activity was Strombolian may become phreatomagmatic if water enters the vent when the magma ejection loses intensity (e.g. Can Tià). there is also Finally, evidence of Strombolian phases in- which sequences, phreatomagmatic obvious into serted can occur if the water supply in the aquifer is momentarily exhausted. Figure 67. Figure 66. 2. El vulcanisme a Catalunya-en baixa 4/6/12 07:09 Página 55 Página 07:09 4/6/12 baixa Catalunya-en a vulcanisme El 2. 2. ElvulcanismeaCatalunya-enbaixa4/6/1207:09Página56

2 l Volcanism in Catalonia is as follows: activity phreatomagmatic involving Garrotxa La the in case frequent an most the during eruption, occurs that styles eruptive of Despite the variety of possible combinations Example ofaneruption Figure 68c. Figure 68b. Figure 68a. Effusive eruptive phase eruptive Effusive Phreatomagmatic eruptive phase eruptive Phreatomagmatic Strombolian eruptive phase phase eruptive Strombolian 56 eeae tobla epoie activity explosive Strombolian generate to gas enough contains still pocket magma the in magma the activity.Nevertheless, tic waterproof and so halts the phreatomagma- vent the makes magma new of ejection The the emissionoflavaflows the eruption is placid and is characterised by stage, final this In sequence. eruptive the to been exhausted, effusive activity puts an end has gas juvenile the of most when Finally, (Fig. 68b) stops momentarily interaction water-magma the which in ses pha- Strombolian pure with interspersed be may activity phreatomagmatic stage, early this In subsoil. the in water the of poration eva- the to due volatiles by enriched is gas juvenile in rich Magma phase. tomagmatic The eruption starts with an explosive phrea- . (Fig. 68a) (Fig. 68c) . . 2 l Volcanism in Catalonia . Rocanegra and Puig Subià volcanoe (Fig. 70) (Fig. . Figure 70. 57 (Fig. 71) 1 1 l Croscat volcanoe La Crosa de Sant Dalmai volcanoe and Puig d'Adri. Both consist of edifices formed edifices of consist Both d'Adri. Puig and 2 l 4 l 2 Figure 71. Figure 69. (Fig. 69) (Fig. During During an eruption, the alternation of types of activity often leads to the formation of different, superimposed volcanic edifices. For instance, in the Natural Park on the volcano of Puig de Martinyà two subsequent cinder cones cover much of a construction. Even so, the best examples of this type of previous phreatomagmatic interference between edifices originating from the same eruption are the volcanoes of La Crosa de Sant Dalmai l volcanic and activity Eruptive edifices The emission of magma through either the crater base or of the the cone drags pyroclasts from one edifice part to of another the and, when seen from above, the shape of the crater resembles a horseshoe. final may vent the of part final the activity, Strombolian During branch, allowing magma to be released through several new vents that form adventive or parasitic cones (1) such as those that surround Croscat On other occasions, volcanic edifices generated in the course of an eruption are partially or totally destroyed by subsequent phases. The cinder cones of volcanoes such as Croscat, Montolivet and Aiguanegra were partially destroyed by lava flows during a final effusive phase by Strombolian activity that have been superimposed on superimposed been have that activity Strombolian by structures. previous phreatomagmatic 2. El vulcanisme a Catalunya-en baixa 4/6/12 07:09 Página 57 Página 07:09 4/6/12 baixa Catalunya-en a vulcanisme El 2. 2. ElvulcanismeaCatalunya-enbaixa4/6/1207:09Página58

2 l Volcanism in Catalonia Figure 72. Volcanic materials l deposits from Puig d’Adri d’Adri Puig from deposits 2 l 5 Phreatomagmatic Phreatomagmatic l Figure 73. Croscat Croscat hss f rpie activity eruptive of phases and pulses different of succession a of result a as sed superimpo- are deposit of types several Garrotxa La In ponents. com- their and rocks pyroclastic the of granulometry the determine hydromagmatic, or magmatic they be origin, their and explosions of types these of lence sityofpyroclastic deposits Explosive volcanic activity gives rise to a great diver- tect duetodenseplantcoverandhumanactivity. few de- to hard are the type) ('a'a flows lava rough-surfaced and smooth usually is surface The ring. lumnar and lenticular jointing and spheroidal weathe- co- of typical are thatfractures the exhibit and black grey- are flows Lava magmas. constituent their of uniformity the to due little very vary activity effusive from resulting rocks Zone, Volcanic Garrotxa La In often sufficienttoidentifythem. is material volcanic of type each of characteristics the Scoria deposits from deposits Scoria 58 (Fig. 74) (Figs. 72and73) Figure 74. materials at La Pomereda La at materials n kolde of knowledge and Sequence of volcanic of Sequence . The vio- The . 2 l Volcanism in Catalonia Strombolian fall Pyroclastic flow deposit. Volcanic tuff deposits. Ash Figure 77. Figure 80. Juvenile fragments and lithics, and fragments Juvenile lapilli-sized and blocks enclo- are They matrix. ash an in sed compacted and fill pre-existing depressions. Angular, Angular, ash-sized vesicular juvenile fragments. They deposit radially around vent, mostly the far from cone. the 59 Distributed around the Strombolian fall crater. Ash and lithics deposits. Scoria Figure 79. Figure 76. Juvenile fragments and lithics, and fragments Juvenile ash-sized or degrees show may Fragments fine of rounding and juvenile pyro- lapilli. clasts are slightly vesicular. Highly dispersed with a high degree of compaction. Angular, Angular, highly mostly vesicular, lapilli-sized juvenile fragments. Often with layers of bombs, they are distributed radially in a small diameter from the vent relatively and form the volcanic cone. Phreatomagmatic fall Strombolian fall Juvenile fragments and lithics of varying size with notable block content. around the crater. Distributed Figure 78. Hydromagmatic explosive activity Hydromagmatic deposits. Breccia Figure 75. deposits. Volcanic agglomerate Juvenile fragments, highly vesicular in general, mostly blocks (bombs), with a variable percentage of lapilli. If found close to the vent, they agglomerate. into welded are Magmatic explosive activity explosive Magmatic fall deposits Strombolian 2. El vulcanisme a Catalunya-en baixa 4/6/12 07:09 Página 59 Página 07:09 4/6/12 baixa Catalunya-en a vulcanisme El 2. 2. El vulcanisme a Catalunya-en baixa 4/6/12 07:09 Página 60 3. Fitxes.en baixa 4/6/12 07:16 Página 61

La Garrotxa Volcanic Zone Sites of volcanic interest 3. Fitxes.enbaixa4/6/1207:16Página62

3 l La Garrotxa Volcanic Zone teria cri- geographical by ordered are descriptions The Interpreting thesitedescriptions Figure 81. morphology. or sequence observable the of interpretation an and present materials the deposits, the ginated the site’s location, the volcano whose eruption ori- of details contains description each Furthermore, dromagmatic explosive. hy- and Strombolian effusive, activity: eruptive of types different of evidence provide sites Volcanic nic features–aredescribed. volca- and landscape - observation Twoof types (Fig. 81) Location of sites of Location to facilitatetheiruseinthefield. 62 Dalmai). in the Llémena Valley (as well as La Crosa de Sant La Garrotxa Volcanic Zone Natural Park and those Sites can be divided into two groups: those within Location ofvolcanicfeatures 3 l La Garrotxa Volcanic Zone Can Tià: an eruption Can Tià: sequence Montsacopa: cone morphology Puig d'Adri: pyroclastic flow 8 4 12 Santa Margarida: pyroclastic deposits Sant Joan les Fonts: massive materials El Clot de l’Omera: a maar La Crosa de Sant Dalmai: pyroclastic surge and breccia 7 3 11 15 63 Turó de la Pomereda: Turó an eruption sequence El Cairat: pyroclastic breccia La Crosa de Sant Dalmai: morphology Location and morphology of the volcanic cones as seen from Puig Rodó 6 2 14 10 Els Arcs Valley: pyro- Els Arcs Valley: Croscat: cinder cone clastic flow Castellfollit de la Roca: lava flows Puig d'Adri: pyroclastic surge 9 5 1 13 Volcanic sites Volcanic 3. Fitxes.en baixa 4/6/12 07:16 Página 63 Página 07:16 4/6/12 baixa Fitxes.en 3. 3. Fitxes.enbaixa4/6/1207:16Página64

3 l La Garrotxa Volcanic Zone base ofthecliff. the stabilise to up build never and spate in is river the when off carried are then These columns. tic the crumbling of the basal- to leading eventually vely, effecti- more can place take weathering where points weak are These cracks jointing. existing the given effective more the all is which thawing), (freeze- weathering frost sion by the river Fluvià and of ero- to due thousands mostly years, for ding rece- been has cliff The nal structure of a lava flow. inter- the of view excellent an provides it kilometre; point and extends for a full highest its at rivers ding surroun- the above m 50 stands cliff basaltic This Turonell. and Fluvià vers ri- the by erosion sequent sub- and flows lava two of superposition the of result a are columns basalt The Castellfollit delaRoca the At exit. Roca la de Castellfollit the at dual-carriageway past Besalú and turn off A-26 the then and Banyoles past C-66 To reach Castellfollit from Girona, take the and theFluviàtonorth. south the to Turonell rivers the between promontory a on Olot from km 7 about The town of Castellfollit de la Roca stands Location andaccess 1 Access timeonfootl Activity typel Point ofinterestl lava flows Castellfollit delaRoca: Effusive Observation ofthebasaltcliff 10 minutes Figure 82. Schematic geological map of Castellfollit de la Roca la de Castellfollit of map geological Schematic 64 basalt cliff. the of foot the reach to footbridge den woo- a over right turn then and m 500 for on h rvr Fluvià river the down leads that 13 Itinerary Park Natural and take Park 45). point (km Oix to road the with junction the at cliff basalt the of view excellent an is there town the to entrance (Fig. 82) Continue . 3 l La Garrotxa Volcanic Zone . (2) . (1) 1 3 The upper part has four layers: the first the layers: four has part upper The b. three, each 5–9-m thick, exhibit marked columnar jointing, while near the top a layer about 9-m thick appears with well- weathering developed spheroidal composed composed of prisms around 50 cm in The diameter. second layer has lenticular jointing and is 3.5-m thick. The final layer again exhibits columnar jointing, but is less than a metre thick and the columns are only 30 cm in diameter the lava gave rise to various differentiated layers within the The lava time flow. lapse between the two lava flows is marked by deposi- the and soil a of development the tion of sedimentary materials that form a layer that clearly separates the two flows. overcome To this obstruction, the waters the eroded have Turonell and Fluvià the of boundary between the basalt materials and the sedimentary rocks. 65 2 Castellfollit de la Roca basalt cliff . This layer divides the cliff into (3) The lower part has three clearly diffe- Figure 83. two parts: a. rentiated layers. The first has columnar jointing, but is partially covered by the ri- is and thick 5.5-m is it vegetation: verside Interpretation Alluvia from the rivers Fluvià and Turonell top on deposited were flows lava two and of the original Eocene substrate. Around 217,000 years ago lava from the volcanoes on the Batet plateau flowed into and along the valley of the former course of the river Fluvià to beyond the town of Sant Jaume de Llierca. Then, some 192,000 years ago a second lava flow flowed down Valley from the Turonell la de Castellfollit to volcanoes Begudà the Roca. In both cases differential cooling of The base of the cliff consists of layers of Eocene sandstone and marl overlain by gravels containing abundant limestone, peb- basalt exceptionally, and, sandstone bles. On top of these materials lies a 40-m- thick layer of black-grey basalt, although about 9 m from the base of the volcanic materials there is a 0.2–1.5-m thick layer of clay and pyroclasts that are recognisable by the abundance of plants growing there Lava flows Lava Description 3. Fitxes.en baixa 4/6/12 07:16 Página 65 Página 07:16 4/6/12 baixa Fitxes.en 3. 3. Fitxes.enbaixa4/6/1207:16Página66

3 l La Garrotxa Volcanic Zone Garrotxa. La the in uncommon are that materials pyroclastic of series a deposited that with several intense stages phreatomagmatic was ted detec- phase eruptive only The centre. eruption the of although south found also are some northwards, mostly extend materials pyroclastic Its origin. tic phreatomagma- of edifice single a of consists that Park Natural the in volcano only the be is to considered It substrate. mentary sedi- Eocene rrounding su- the into sunk is which of diameter,in crater m 120 around a possesses It plateau. Batet the from and Begudà from visible is - structure in maar-type – Cairat El of crater The El Cairat Sant to Roca la de Castellfollit from GI-522 the take quarry, the reach To ferent sites. dif- of number a in visible are today and Barranc Can at quarried were volcano this by emitted materials pyroclastic the 1980s, the During Aiguanegra. of cano vol- the to connected is which Molera, de Sierra the of ridge the on lies Cairat El of volcano the of centre eruption The Location andaccess 2 Access timeonfootl Activity typel Point ofinterestl pyroclastic breccia El Cairat: Phreatomagmatic Can Barrancquarry 5 minutes Figure 84. Schematic geological map of El Cairat Cairat El of map geological Schematic 66 excavated banks the in visible deposits volcanic the to and quarry the into track the up metres 100 about walk and road the of side other the on estate industrial the in Park Joan, a track turns south into the quarry. Sant before kilometre A Fonts. les Joan (Fig. 84) . 3. Fitxes.en baixa 4/6/12 07:16 Página 67

Pyroclastic breccia

Description The sequence of volcanic materials rests A detailed analysis of these volcanic de- on brown silt and clay, which appear next posits reveals black juvenile fragments to the track by a small spring. Above with little vesiculation, mixed with lithics these layers lies a fragmentary volcanic of diverse composition. The most plenti- deposit noteworthy for its diverse granu- ful lithics are the red clays and conglo- lometry, with clasts of a wide range of merates originating from the Bellmunt for- sizes (from millimetres to metres across). mation, the bluish marls from the This deposit is 10-m thick here and has Banyoles formation and the sandstones, no clearly visible stratification, although silts and marls from the Bracons forma- alternating, various-sized fragments diffe- tion, all of which are local Eocene sedi- rentiate a series of layers of irregular mentary deposits. thickness. These layers slope gently northwards and are affected by normal faults.

Figure 85. Barranc quarry 3 l La Garrotxa Volcanic Zone

Interpretation The phreatomagmatic eruption of El Instantaneous and constant remobilisa- Cairat ejected mostly pyroclastic brec- tion of the pyroclasts building up at the cias, although there is evidence of some top of the volcano occurred. During its more violent pulses that generated pyro- movement on the northern flank, this clastic surges. The location of the erup- avalanche of fragmentary materials was tion centre on a ridge-top with steep slo- channelled into a gully, where heavy ero- pes on all sides permitted the build-up of sion swept away part of the sediments volcanic materials: the ejected pyroclasts lying on the stream-bed. slid down the mountainside to a more stable area, where they were deposited.

67 3. Fitxes.enbaixa4/6/1207:16Página68

3 l La Garrotxa Volcanic Zone the site. of history geological the reconstruct to us allows also and structures nal inter- their and flows lava the between interaction the revealed has century twentieth early the in salt ba- for river- Quarrying beds. former the cupy oc- partially that flows lava three of perposition su- the uncovered has rivers Fonts. these by les Erosion Joan at Sant Fluvià river the flows into Bianya river The Sant JoanlesFonts has revealed a sequence of lava flows. erosion river Fondo, Molí at Fluvià, the of bank left the on Finally, Fontfreda. same river lies the abandoned quarry of early in the twentieth century. Along the abandoned quarry basalt a of workings the by exposed was and Bianya river the of bank El right the visiting. on lies worth Boscarró well all les Joan are Sant Fonts in sites three These Location andaccess 3 Access timeonfootl Activity typel Point ofinterestl massive materials Sant JoanlesFonts: Effusive volcanic materialsatElBoscarró, ElMolíFondoandFontfreda 30 minutes Figure 86. Schematic geological map of Sant Joan les Fonts les Joan Sant of map geological Schematic 68 ie cn e ece o fo along Natural 16 Park Itinerary foot on reached be can the sites where from square, main the the in after Park Fonts. les Joan Sant to signs llow fo- just and tunnels and viaduct Castellfollit La dual-carriageway A-26 towards the leave Girona, GI-522 From Canya. the take from Fonts Olot, les Joan Sant reach To (Fig. 86) . 3 l La Garrotxa Volcanic Zone . (2) . (3) 2 1 3 Feature Molí Fondo Figure 87. Finally, Finally, at the top the third Boscarró visible is flow lava and and basalt pebbles in a silt matrix The cliffs at Fontfreda Fontfreda at cliffs The The visible layers here correspond to the third lava flow that we visited at El obvious has layer lowest The Boscarró. columnar jointing with columns over 3- m high and is crowned by an area of lenticular jointing. Boscarró, a clear transition from one Unlike type of jointing to the next is visible. at El 69 . In parts, the rough cinder base pro- base cinder rough the parts, In . trudes. On the nearby cliff, you can see can you cliff, nearby the On trudes. the rest of the lava flow exhibiting columnar jointing. Just above lies a layer of sediment consisting of sandstone (1) Description Boscarró El This site provides excellent views of different types of jointing in the last of the three lava flows that were channelled along the Fluvià Valley. Five layers can be distinguished: the lowest exhibits columnar jointing with five- and six-sided columns, 20–40 cm in diameter 2–3-m and high; the second and fourth layers have slab jointing and are separated by a third layer in which the massive material shows very few cooling cracks; the fifth finally, and just uppermost layer, below soil level, has been more altered the to proximity its to due others the than surface and consequently exhibits clear spheroidal structures. can we quarry, the of side other the On see where the river Bianya has been channelled along the point of contact between the volcanic materials and reddish Eocene sedimentary materials. Molí Fondo The dam was built on top of the first lava flow, which lies on the bed of the Fluvià. the To right a certain degree of columnar jointing can be seen in the basalt, which is blue-grey in colour. If river the along downstream wander you bank, you walk on slabs that represent the base level of the second lava flow Superposition of lava flows of Superposition 3. Fitxes.en baixa 4/6/12 07:16 Página 69 Página 07:16 4/6/12 baixa Fitxes.en 3. 3. Fitxes.enbaixa4/6/1207:16Página70

3 l La Garrotxa Volcanic Zone is stillunclear. second lava flow, whose origin a by occupied was riverbed the later, years of Thousands ted sedimentsontop. from this lava flow and deposi- riverbed new a out gouged river the of activity erosive The lling inpartoftheriverbasin. the former bed of the Fluvià, fi- into and down Batet flowed plateau the of volcanoes the from issuing flow lava first The Interpretation Figure 90 Figure 89 Figure 88 70 3 l La Garrotxa Volcanic Zone Over time, the river deposited more sedimentary materials top on pebbles) and sand (silt, of the second lava flow and terrace. formed a river About 133,000 years ago, a third lava flow covered these latest alluvial sediments. This final lava flow originated from just stopped and Garrinada La les Joan Sant of town the past Fonts. Fondo Molí of diagram Schematic today. 71 Figure 93 Figure 92 Figure 91 3. Fitxes.en baixa 4/6/12 07:16 Página 71 Página 07:16 4/6/12 baixa Fitxes.en 3. 3. Fitxes.enbaixa4/6/1207:16Página72

3 l La Garrotxa Volcanic Zone wards towardstheriverFluvià. tion by a small lava flow that flowed north- subsequent erup- the of stages final the a in destroyed during partially then was but phase, Strombolian formed was ring its eruption. However, its cinder cone du- occurred phases phreatomagmatic of number a here, found deposits the by and its horseshoe-shaped crater. Judging Bisaroques stands plateau Batet the of slope northern the on south-east the To wards thenorth-east. to- opens crater its Pinya; La of ridge the onto abutting cone cinder a and of consists south-west the to lies Montolivet slopes. northern and southern its on volcano, the of top on visible craters two other the to subsequent the Strombolian phases, which also gave rise during cone constructed cinder a by covered completely almost is ring tuff This base. its at ble visi- is phase, phreatomagmatic a during originated that ring tuff a of part crater, first The Garrinada. La of craters three canoes of Montolivet, Bisaroques and the vol- the of views excellent provides crater the around walk A cone. cinder shaped regular-single, a of consists volcano This View from Montsacopa Sant of and twowatchtowers. chapel century, the nineteenth the in built Francesc, stands top On south-west. the to Montolivet and east north- the to Garrinada La between city the of middle the in lies itself, Olot within volcanoes four the of one Montsacopa, Location andaccess 4 Access timeonfootl Activity typel Point ofinterestl cone morphology Montsacopa: Strombolian Volcanic crater 10 minutes 72 penetrated onitsascenttothesurface. magma the which through fracture single a along positioned are Garrinada La and The volcanoes of Montsacopa, Montolivet Volcano the the top of the volcano at starts to climbs and town the crosses Museum, 17 Itinerary Park Natural Zone Volcanic Garrotxa La crater. the to steps the up walk then and quarry abandoned an near cone the of base the at cemetery the at park can you walk, the Figure 94. volcanoes Schematic geological map of the four Olot four the of map geological Schematic (Fig. 94) . To shorten 3. Fitxes.en baixa 4/6/12 07:16 Página 73

Morphology of the cinder cone

Description The crater of Montsacopa is circular, tion. In the quarry next to the cemetery about 120 m in diameter and 12-m the different layers formed during the deep; its cone has sloping flanks and eruption have been exposed. Most stands 94 m above the surrounding consist of block- and lapilli-sized frag- land. The bottom of the crater is flat ments, with the occasional encrusted and is currently cultivated. bomb. These are highly vesicular juve- On the southern and south-eastern nile pyroclasts. However, at the top of flanks of the cone there are a number the sequence of materials, despite of abandoned quarries, exploited in the consisting of solidified magma, some sixteenth century for pyroclastic depo- of the deposits exhibit incipient vesicu- sits that were mostly used in construc- lation and are mostly ash-sized.

Figure 95. Montsacopa 3 l

Interpretation La Garrotxa Volcanic Zone There were at least two eruptive phases - lar in the upper layers of the sequence in- one effusive, the other explosive - during dicates the existence of phreatomagmatic the eruption of Montsacopa. During the pulses, which destroyed part of the lava first phase, a lava flow ran to the foot of flow and created fragments that were de- the nearby ridge of Sant Valentí and a posited as lithics in the pyroclastic surge. large section with lenticular jointing is visi- The Strombolian phase eventually built ble next to Olot football club (although the the cinder cone and the lack of a final ef- proposed itinerary does not go there). fusive phase with the emission of a lava The second phase was mostly flow ensured that the crater's circular Strombolian, although the presence of shape was preserved. fragments that are not particularly vesicu-

73 3. Fitxes.enbaixa4/6/1207:16Página74

3 l La Garrotxa Volcanic Zone k. h beechwood d’en Fageda La The as known km. 6 for west ran it as crater ped horseshoe-sha- a formed and edifice the of symmetry the destroyed that flow effusive lava basanite a generated The phase de Puig Martinyà. and Santa Margarida of volcanoes arby ne- the pyro- covered that second clasts ejected and cone The the built phase Strombolian two fusive. first ef- last the and Strombolian the phases, three in erupted Croscat tern flank. wes- its on crater shaped horseshoe- a by distorted nical-shaped cinder cone is ter.co- its of symmetry The diame- in m 950 Iberian measures base its and the ) Peninsula in volcano tallest the is (it land ding surroun- the above m 160 stands Croscat of top The Croscat ture ofacindercone. struc- internal the reveals that interest nal exceptio- of site a is volcano the of flank northern the on quarry abandoned The plateau. basaltic Batet the by north the to and Mont del Julià Sant of mountain the by north-east the to ridge, Finestres Corb- the by south the to bounded area flat relatively a in Pau Santa of village the and Olot between halfway lies Croscat Location andaccess 5 Access timeonfootl Activity typel Point ofinterestl cinder cone Croscat: Strombolian Quarry withvolcanicdeposits 20 minutes Pomereda gives an age of age an gives Pomereda La at materials ejected the of Dating blisters. numerous flow,lava by dottedis which rough this on stands Jordà Figure 96. Schematic geological map of Croscat of map geological Schematic 74 omto cnr a Cn Passavent starts here Can at centre formation in- Park Natural the and Croscat to 15 Itinerary Olot. leaving after km 7 right) the (on park car Margarida Santa de Àrea the in park and Pau Santa wards to- GI-524 the take Croscat, reach To (Fig. 96) i atvt i te whole the Catalan volcanicfield. in activity nic volca- of manifestation cent re- most the thus is Croscat and years) (±1,500 11,500 . 3. Fitxes.en baixa 4/6/12 07:16 Página 75

Structure of the cinder cone

Description The quarry in Croscat was worked from cular juvenile fragments that are mainly la- the late 1950s to the early 1990s and pilli-sized (Fig. 97). The gradient of these today provides wonderful views of a layers increase as you move from the vast surface area of pyroclastic mate- centre to the outside of the cone. At the rials, approximately 150 x 500 m. The base of the sequence, where bombs are terracing on the right of the open face more abundant, different layers alternate. dates from when the quarry was active The materials are mostly dark grey or and has helped stabilise the deposits. black, although in the area closest to the On the opposite side and in the middle centre of the edifice they are reddish of the deposits, however, landslips are ochre (1). more frequent. In the lowest part of the former quarry, It is easy to spot the different layers of there is a layer of red welded scoria (2). scoria, made up of irregular, highly vesi-

Figure 97. Croscat volcanic deposits

Interpretation 3 l La Garrotxa Volcanic Zone The first phase of the eruption was ejected. Finally, a lava flow was emitted Strombolian and explosive and built the from the eastern flank of the cone and welded scoria deposits recognisable ran westwards towards Olot. near the vent at the base of the se- The different colours of the pyroclasts quence. This activity then became are due mainly to thermal alteration. more explosive and built the cinder Hot gases released in the later stages cone. Initially, the pyroclasts fell in of the eruption caused oxidation practically horizontal layers, but with around the chimney, the hottest part of the gradual growth of the cone the gra- the volcano; the black-grey of the pyro- dient of the deposits began to increa- clasts thus changed to red-ochre. se. Sporadically, when the release of gases was less intense, bombs were

75 3. Fitxes.enbaixa4/6/1207:16Página76

3 l La Garrotxa Volcanic Zone ned with Santa Margarida, Croscat and A map shows that La Pomereda is alig- shape. in tumulus-like was cone small this tre, cen- its from materials the of quarrying the to Prior cones. parasitic or ventive ad- small five volcano’s the of one is area raised slightly this and Croscat of foot the at lies Pomereda la Turóde El Turó delaPomereda clastic depositscoveredbyalavaflow. pyro- of sequence a reveal walls quarry TuróThe extracted. were Pomereda la de of volcano the by emitted materials canic lies another former quarry, from which vol- Next to Can Genís in the Massandell plain Location andaccess Figure 98. 6 La Pomereda volcanic deposits volcanic Pomereda La Access timeonfootl Activity typel Point ofinterestl an eruptionsequence El Turó delaPomereda: Strombolian andeffusive Volcanic materials 30 minutes 76 Catalan volcanic field. the in activity volcanic of manifestation recent most the thus is and old years 11,500 at dated been has flow lava Its posedly runsnorth-westtosouth-east. sup- that fault a on lies and Astrol Puig La about 20malongontheleft towards visible is track quarry abandoned The Canova. right-hand the of side take north the Croscat. Where the route forks at Can Pelat, skirts which Jordà, Santa d’en de Fageda La towards park car Margarida Àrea the from 1 itinerary Park Natural take Pomereda, la TuróTode reach 1 (Fig. 96) . 3 l La Garrotxa Volcanic Zone , alt- (2) . Here, (1) appears, so- appears, (3) 3 mewhat channel-shaped and about 2-m thick in its middle. The base of this small dis- structure internal its and scoria is flow plays columnar jointing with poorly defined columns. the clasts are mostly lapilli-sized The next Strombolian and phase gave rise to a deposit of was lapilli-sized also scoria and ash. The thinness typically of these deposits, which here are found very near the vent, indicates that this second phase was short lived. The final phase was effusive and emitted a small lava flow that partially covered the top of the underlying pyroclasts. The transfer of heat from this layer to the lapilli below caused the pyroclasts to weld together. hough there are some larger fragments towards the top. In the final 30 cm the lapilli fragments are welded. deposit massive a Finally, On top of these fragments lies a 3-m- thick layer of dark grey scoria 77 . This deposit consists of highly of consists deposit This . 2 Interpretation The eruptions of both La Pomereda and Croscat began with Strombolian phases that were not very explosive. In the course of the eruption, scoria blocks semi-molten state in were ejected and a wel- vent. the to close fell they as together ded The initial phases of the eruptions at this in La began both Croscat and Pomereda fashion and the deposits that constitute a volcanic agglomerate. formed The south-western part of the quarry holds the best outcrop of volcanic agglomerate in the Catalan volcanic field (Fig. 98) Massive and fragmentary materials fragmentary and Massive Description vesicular juvenile fragments, mostly blocks (bombs) with a variable percen- and welded is scoria This lapilli. of tage continuous towards the northwest; it is largely dark grey to black, although in appear. fragments reddish parts 3. Fitxes.en baixa 4/6/12 07:16 Página 77 Página 07:16 4/6/12 baixa Fitxes.en 3. 3. Fitxes.enbaixa4/6/1207:16Página78

3 l La Garrotxa Volcanic Zone rials somewhat hides the hides somewhat rials mate- volcanic the ring cove- vegetation The all. at explosive barely was times at and intensity in greatly varied which vity, by phreatomagmatic acti- uneventful followed quickly was and rather was Margarida Santa of tion erup- the during phase Strombolian initial The dern times. mo- in restored heavily been has which crater chapel, Romanesque a the stands of the In middle stratum. canic pre-vol- the in imbedded is crater the since rials, mate- volcanic formed of entirely not is cone Its marls. Eocene on stands diameter and 70-m deep, in m 350 about is crater circular whose phreatomagmatic volcano, This Santa Margarida that track a along right turn m, 200 just after Pau; Santa towards heads and park car the in starts Margarida Itinerary 4 leading to the crater of Santa up thevolcano. and walk point on the GI-524 (Olot to Santa Pau) 8-km the at car-park Margarida de Santa Àrea the in Park ridge. Lleixeres the foot of a spur jutting south from the best- the known volcanoes in of La Garrotxa, lies at one Margarida, Santa Location andaccess 7 Access timeonfootl Activity typel Point ofinterestl pyroclastic deposits Santa Margarida: Phreatomagmatic andStrombolian Volcanic depositsalongtheroad toMaselCros 15 minutes of thevolcano. sector south-eastern the in flow pyroclastic small Figure 99. Schematic geological map of Santa Margarida Margarida Santa of map geological Schematic 78 400 metresfurtheron the best sequence of deposits is found although immediately, appear roclasts py- road the of side right-hand the On volcano. the of sector eastern the and crater. Cros el Mas towards continue and turn right the this ignore to is materials canic to vol- the up see to way best the However, steeply leads (Fig. 99) . 3. Fitxes.en baixa 4/6/12 07:16 Página 79

Pyroclastic fall and surge deposits

Description Three types of volcanic materials appe- sandstone, while the predominate frag- ar along the road to Mas el Cros, one ments in the latter are black and slightly succeeding another from right to left as rounded in shape with little vesiculation a result of the inclination of the layers (2). The sequence is crowned by a de- (Fig. 100). On top of the silty pre-volca- posit that looks very like the previous nic soil, sits a layer of compacted ash. layer, only without any lithics, and con- Then, black juvenile fragments appear, sists of a fine-grained scoria deposit containing quite rounded, reddish- with no stratification (3). brown lithics (1). Finally, there is a layer of lithic and juvenile lapilli-sized fragments; the former consist mostly of red

2 1

Figure 100. Outcrop on road to Mas el Cros

Interpretation The volcanic map of this sector of the is practically Strombolian, although the

Volcanic Zone reveals that not all the presence of lithics indicates there was 3 l

deposits found here originated from some degree of phreatomagmatic acti- La Garrotxa Volcanic Zone Santa Margarida. vity. The dispersion of this material is The base layers correspond to pyro- radial, from the vent outwards. clastic surges expelled during the ph- Finally, the scoria at the top of the de- reatomagmatic eruption. They were posit corresponds to a Strombolian fall mainly dispersed eastwards by the in- deposit that originated from Croscat, a teraction between the magma and kilometre away. From the absence of water in the aquifer in the Bellmunt for- any paleosol between these different mation (Eocene). The middle layer also layers we can deduce that the erup- consists of deposits from Santa tions of Croscat and Santa Margarida Margarida, but from a far less violent took place simultaneously. subsequent eruption. This fall deposit

79 3. Fitxes.enbaixa4/6/1207:16Página80

3 l La Garrotxa Volcanic Zone from resulting a pyroclastic flow. possibly tuff, volcanic a is there where Iscle, Sant of valley the of part filled has deposit pyroclastic largest eruption. The a of Strombolian product the are some but atomagmatic, phre- are Most roclastic. py- are materials ejected the all therefore and ses pha- effusive no had tion erup- Tià Can The south. low cone is highest to the The deep. 20-m depression, around flat- bottomed this pasture mals ani- Today,ter.domestic cra- 270-m-diameter lar, circu- a with edifice type maar- a has and Tuta La and Fontpobra of those to next lies volcano This The volcano to (Olot GI-524 the on point 5-km the at Xel Can opposite park Tià, Can Toreach right nexttothehouseofCanTià. quarry abandoned small a in made be will observations our of most However, sible. vi- are materials ejected its of many where Colltort, de Iscle Sant of valley the of head the at is stands vent Its ridge. Lleixeres Corb- the of top the to close farm a from name its takes Tià Can of volcano The Location andaccess 8 Access timeonfootl Activity typel Point ofinterestl eruption sequence Can Tià: Phreatomagmatic andStrombolian Can Tiàvolcanicdeposits 60 minutes Figure 101. Schematic geological map of Can Tià and its volcanoes its and Tià Can of map geological Schematic 80 cano in about an hour an about in cano 5, Itinerary which leads straight to the vol- Park Natural take and road) Pau Santa epciey t te elut and Bellmunt the Folgueroles formations. to respectively, corresponding, strata, uppermost the in browner then sedi- and reddish initially Eocene ments, over pass you up, way (Fig. 101) . On the On . 3 l La Garrotxa Volcanic Zone . (3) . (1) Eruption sequence at Can Tià . (2) Figure 103. Finally, there is a veryFinally, compact tuff deposit that can be followed downhill for more than a kilometre On top of the scoria lies a series of alternating layers of breccia and ash. Here, the juvenile fragments display incipient vesiculation and are slightly rounded. The abundant lithic most fragments in the first layers are brown and correspond to the Eocene sandstones of the Folgueroles formation. The lithics in the breccia and are but too, ash sandstone mostly are part in upper the reddish in colour and originate geological same the from from formation Bellmunt the epoch made made up of lapilli-sized fragments and blocks and is notably vesicular. A few diame- in cm 10 to up measuring lithics ter are present 81 that for- 3 are around 10- around are with breccia and (Fig. 103a) 2 (Fig. 102) (Fig. The quarry at Can Tià . In this phase of the eruption, (Fig. 103b) 1 Figure 102. pyroclastic surges. These explosions in explosions These surges. pyroclastic the vent in this second phase destroyed the cinder cone and the construction of the maar began. The deepening of the area of magma water- interaction meant that from the water Bellmunt aquifer could also in- tervene in the phreatomagmatic activity (Fig. 103c) Interpretation The eruption of Can Tià began with a Strombolian phase The sequence of deposits in the small quarry Tià Can The eruption sequence eruption The m m thick and contains two sets of frag- mentarymaterials. At the base (around 6–m thick) there is a black scoria deposit with no layering med a cinder cone built by scoria fall deposits. When the pressure in the vent drop- ped, the magma interacted with the water in the Folgueroles giving aquifer, rise to a more violent phreatomagmatic eruption a pyroclastic flow was formed from different surge- and breccia-type flows. Description 3. Fitxes.en baixa 4/6/12 07:16 Página 81 Página 07:16 4/6/12 baixa Fitxes.en 3. 3. Fitxes.enbaixa4/6/1207:16Página82

3 l La Garrotxa Volcanic Zone canoes intheSantaPauarea. vol- other from originating flows lava the under disappears deposit Ser,this river the with valley Arcs the of confluence the At m). 7.5 (about part upper its in thickest is it m; 350 of width maximum ted a deposit at least 1.7-km long with a genera- last the which of phases, tivity Sant Jordi had a number of different ac- bably buried the volcano’s edifice. the pro- have and valley of the of part upper slopes the along up built northern have ridge Finestres the from and piedmont sediments washed down alluvial Numerous deposits. roclastic above 475 m, the upper limit of the py- lies crater the that clear is it although valley, this of shape the mould helped has that fracture north-south the on lie may It located. been yet not has vent its since known, are volcano this by emitted deposits pyroclastic the Only Sant Jordi near MaselCarrer. streambed the in viewed be can that rials mate- volcanic of outcrops of series ted interrup- an contains valley the of bottom The ridge. Finestres the of slope northern the on lies Arcs Els of valley small The Location andaccess 9 Access timeonfootl Activity typel Point ofinterestl pyroclastic flow Els Arcs Valley: Phreatomagmatic Volcanic depositsatMaselCarrer 60 minutes 82 bed stream- the to down leads that right the to track a along m 10 about for continue Carrer, el Mas At Valley. Arcs Els wards to- 7 Itinerary Park Natural follow and Pau Santa in park deposits, these reach To Valley Figure 104. (Fig. 104) Schematic geological map of Els Arcs Els of map geological Schematic . 3. Fitxes.en baixa 4/6/12 07:16 Página 83

The pyroclastic flow

Description Water erosion in Els Arcs valley has revealed a complete sequence of materials ejected by Sant Jordi. In the upper part of the valley, the pyroclastic materials rest on gravel with sandstone pebbles and a sand and silt matrix. Three fragmentary deposits in 12 dis- cernible layers are visible (Fig. 105): at the base lies a first deposit comprising two very compacted layers, each measuring 5 cm, with ash-sized juvenile fragments and lithics (red sandstone from the Bellmunt formation). The upper layer has coarser, lapilli-sized clasts (1) 3 underlying a deposit of scoria including some ash with juvenile components and the same red sandstone lithics (2). The final deposit has four layers with a total 2 thickness of 7.5 m, with two layers at 1 the base, each 5-cm thick, consisting of lapilli-sized clasts and ash with juvenile components and red sedimentary lithics. The most noticeable layers of this sequence are the topmost two, two- and four-metres thick, respectively. Both Figure 105. Outcrop El Carrer are tuffs with juvenile fragments and lithics, some over 10 cm in diameter, and are embedded in a matrix of red ash (3). The base of the final layer is erosive and is flat-topped.

Interpretation

At least three phases occurred during As the eruption was ending, the phrea- 3 l the eruption of this volcano, of which tomagmatic phase reactivated, genera- La Garrotxa Volcanic Zone the phreatomagmatic events were the ting a pyroclastic flow that ran into the most important. former course of the valley. The two la- In the first, the water-magma interac- yers of tuff correspond to the two pul- tion led to pyroclastic surges that for- ses that took place while the pyroclas- med the base deposit. Then, the phre- tic flow was being formed. The rapid atomagmatic activity was interrupted emplacement of this flow meant that at by a Strombolian phase, which emitted the front there was a significant inges- the scoria. In this phase, however, tion of cold air. This air heated up im- small amounts of water entered the mediately due to the high temperature vent and caused small pyroclastic of the flow and caused a series of ex- flows. plosions, which created the pyroclastic surges that gave rise to the layers forming the base of the third deposit.

83 3. Fitxes.enbaixa4/6/1207:16Página84

3 l La Garrotxa Volcanic Zone goons were drainedforcultivation. goons la- and plain marshy the century enth gradually began to silt up and in eighte- lake the time, Over lake. barrage a as river Fluvià, giving rise to what is known the dammed and Olot towards down ran Croscat by emitted flow lava The lake. a once was that plain agricultural excellent views of the Bas valley Bas the of views excellent offers Xenacs to leads that road The The Basvalley Bas Valley the and Trough Olot the of most Pyrenees, pre- the Pyrenees, main the Park, Natural Zone Volcanic Garrotxa La of views llent exce- the are there Area, from Recreational Xenacs where, ridge Corb the of end western the at stands m) (909 Rodó Puig Location andaccess along a road which climbs steeply in 5 left km to turn m, 300 about After Preses. Les of town the through C-152 the take Olot, From Figure 106. 10 (Fig. 106) View from Puig Rodo at Xenacs at Rodo Puig from View Access timeonfootl Activity typel Point ofinterestl cones asseenfrom Location andmorphologyofthevolcanic 6 . Strombolian andeffusive View from theviewpoint 20 minutes (1) , an , 84 oes t msl te beechwood the mostly known as La Fageda d'en Jordà it, covers that woodland the by landscape the across flow lava the Croscat the trace of route can we Rodó, Puig From Les Preses, also climb up to Xenacs. Natural Park Itineraries 10 and 11, starting in TownPreses Les Council. from obtained be can permit access an although weekdays, on vehicles all to closed is and coaches for viable not is road The viewpoint. Rodó Puig the to path signposted the along walk here, From area. recreational the in park car the 1 Puig Rodó 3 8 volcano Racó (2) . Montolivet volcano 8 3 l La Garrotxa Volcanic Zone . 8 5 (7) Santa volcano Margarida .The de- 8 (6) Costa volcano Puig de la 8 volcano Puig Jordà to the north-east, for- north-east, the to 8 (9) volcano Croscat lying the closest to Puig 2 Garça volcano 8 Puig de la 8 Mountains Mountains of La Serralada Pujalós volcano and are part of this transversal (N-S of the park’s 40 volcanoes. A charac- 8 (8) (5) teristic feature of the volcanic cones is their shape and the form of their craters, either circular or horseshoe-shaped. All are covered in woodland and almost al- that land arable the above out stand ways is note Of bases. their to up right reaches plateau Batet the can see almost the whole of the northern sector of the volcanic zone, including 14 Transversal: ridge Corb the include peaks these Rodó, fected by faults during the Alpine oro- geny. c. pression at the foot of Puig Rodó to the the Olot Trough north corresponds to running) system, also made up entirely of Eocene rocks. These mountains consist of a series of raised and sunken blocks, the product of a system of normal faults, the highest of which are the peaks Collsacabra of and Puigsacalm med by the build-up of successive lava flows from the region’s oldest volcanoes, most of which have been eroded away. volcano 85 9 Puig Astrol 8 8 Cabrioler volcanoes the backdrop to these mountains these 8 volcano Bisaroques 4 volcano 8 Garrinada Pre-Pyrenees Pre-Pyrenees and Sub-Pyrenees Axial Pyrenees (3): The Olot Trough The depression Garrotxa bordered to the north, the Corb by ridge to the south, Sant Julià del Mont to the east L’Alta and La Collsacabra and Puigsacalm to the west is known as the Olot Trough. Behind and to the sides of this depression of tectonic origin stand most of the Zone. Volcanic Garrotxa La in volcanoes The valleys we can see are all U-shaped because they were filled in by lava flows emitted during eruptions or by sediments that built up behind the barrage lakes formed by lava flows. From Puig Redon we The main relief features relief main The On a clear day from Puig Rodó you can see most of La Garrotxa, as well as parts of El Ripollès to the west and El To east. the to Empordà Pla L’Alt and l’Estany de can make out: the north we a. the view north consists of the main ridge of the Pyrenees, made up Palaeozoic of rocks, whose ancient highest peaks much of the year. are snow-covered for b. (4): Garrotxa) (L'Alta (1,000–1,500 m) lie in front of the Axial of the in front m) lie (1,000–1,500 Eocene of consist mostly and Pyrenees af- and folded intensely were that rocks 8 volcano Montsacopa 7 3. Fitxes.en baixa 4/6/12 07:17 Página 85 Página 07:17 4/6/12 baixa Fitxes.en 3. 3. Fitxes.enbaixa4/6/1207:17Página86

3 l La Garrotxa Volcanic Zone (Fig. 107) Boc del Banya la de Puig volcano, her vered by a lava flow originating from anot- co- partially is edifice volcanic small This El Clotdel’Omera la de Mas to runs track a Joan, Sant de Pla El before just point, 15-km the GI-531 along the Llémena valley and at To reach the area, from Girona take the llage ofLloràandElPladeSantJoan. vi- the between Llémena river the of bank left the in on depression circular a Catalan), depression = (clot l’Omera de Clot El inside lies Pallonera, la de Mas farm, A Location andaccess ran south as far as the river Llémena and Llémena river the as far as south ran flow lava third A (eastwards). Boé Pere Can and de south-west) the Torrent (to Bosquerós of streambeds former the into flowed which of two flows, lava three to rise gave phase effusive the Finally, crater. elliptical an with bombs and lapilli of cone cinder a built and began Boc del Banya la de Puig of phase Strombolian the Subsequently, erupted. l’Omera de Clot El phases, phreatomagmatic these as time same the As Llémena. river the and Bosquerós, de Torrent stream, a of banks the along seen be can that clasts pyro- the emitted phase reatomagmatic then ph- finally,The and, effusive. Strombolian phreatomagmatic, was eruption the Initially, occurred. phases different eruption of series a Boc del Banya la de Puig of formation the During materials. metamorphic Palaeozoic with contact into come materials sedimentary Tertiary where fault, Llorà the on lies Boratuna, into the south-facing slope of La Serra de 11 Ti lte vlao encrusted volcano, latter This . Access timeonfootl Activity typel Point ofinterestl maar El Clotdel’Omera Phreatomagmatic View ofthecrater 5 minutes 86 Pallonera crops of volcanic materials. just before the farm has interesting out- stream a track, the along continue you If l’Omera. de Clot El over views good are there where from clearing, a as far as track the along walk and Joan Sant hic rock. metamorp- of hill small a Llorà, Els de Rasos by Boc del Banya la de Puig separated from l’Omera, de Clot El stands plain this to Next Joan. Sant de Pla El as created the agricultural plain today known Banya delBocandElClotdel’Omera Figure 107. Geological diagramofElPuigdela (Fig. 107) . Park in El Pla de Pla El in Park . 3 l La Garrotxa Volcanic Zone del Boc Puig de la Banya El Clot de l’Omera and Puig de la Banya l’Omera El Clot de Figure 108. del Boc posits around the crater that increase in thickness from north to south. In a small streambed behind Mas Pallonera, de a sequence of la pyroclastic materials, 10-m thick in parts and consisting of a succession of breccia and ash deposits, is visible. They are very heterogeneous in composition due to the size and type of lithic fragments. general in angular very are lithics These and originate from metamorphic rocks (e.g. schist and marble). A few basalt fragments are mixed in vesiculation. little show and mostly 87 (Fig. . Today, . a Today, drainage channel pre- 108) Interpretation The edifice of El Clot de l’Omera consists of a maar that was formed during a single-phased eruption. The phreatomagmatic ejecta southwards extend owing to the steep mainly slopes of Els Rasos de Llorà to the north of the volcano, although this asymmetry inclina- the by caused been have could tion of the fracture magma from issued. The which flat bottom the of the crater is due to the blocks of pyroclastic materials that slid down from the crater rim. One of these blocks did not its of evidence and completely stabilise movement can be seen in the scar of the circular fracture Pallonera. la de Mas behind in the stream Alternating layers of ash deposits and series the to due visible very are breccia of different pulses that occurred during con- deposits the of Some eruption. the can and lithics of percentage high a tain thus be attributed to phreatomagmatic pulses. The fact that most of the lithics are metamorphic in origin suggests that a large aquifer existed in the substrate of the metamorphic rocks. The most notable feature of this volcano is the crater in its single volcanic edifice, which abuts the southern slopes of Els Rasos de Llorà; on its inner walls metamorphic materials appear underneath the pyroclastic deposits. Thus, the crater which lies below the pre-eruption land surface is flat-bottomed, and measures approximately 500 m in diameter and is 20-m deep Maar Description vents the crater from flooding. vents the crater from The cone is partly covered by a lava flow and is difficult to see. However, there is a sequence of pyroclastic de- 3. Fitxes.en baixa 4/6/12 07:17 Página 87 Página 07:17 4/6/12 baixa Fitxes.en 3. 3. Fitxes.enbaixa4/6/1207:17Página88

3 l La Garrotxa Volcanic Zone on theoutskirtsofGirona. Domeny to km 11 flowed that flow lava a generated eruption the of stage last the in lava of emission An vent. the from km 5 to up sed and there are deposits disper- well are They ried. tivity are numerous and va- ac- phreatomagmatic no’s volca- this of products The Canet d’Adri. in church the behind just from visible is and three the mostremarkableof is m 408 reaching cone cinder A identified. be phases, can eruption ferent which were built during dif- ai edifices canic vol- superimposed Three Girona. of city the from km 7 only the Llémena Valley and lies in volcanoes the of most eastern- the is This Adri. and d’Adri Canet of village the of between Rocacorba, mountain the of foot the at stands volcano This Puig d’Adri Rissec de Torrent and Rocacorba de Riera streams, two of confluence the at out gushes that Gironès) (El d’Adri Canet of village the Font de la Torre is a natural spring near Location andaccess this town, turn right on the GIV-5313 to past km 3 about and Gregori Sant to the spring from Girona, take the GI-531 12 Access timeonfootl Activity typel Point ofinterestl pyroclastic flow Puig d’Adri: (Fig. 109) Phreatomagmatic (Fig. 109) Volcanic materialsdepositedatFontdelaTorre , 5 minutes Figure 109. . To reach To . Geological diagram of Puig d’Adri Puig of diagram Geological 88 Riera de Rocacorba. of bed the in spring the to track the up pick and farm la this to de next Park Mas Torre. to leads d’Adri Canet of on the left about 300 m after the centre street The d’Adri. Canet of village the 3. Fitxes.en baixa 4/6/12 07:17 Página 89

The pyroclastic flow

Description Compacted fragmentary materials (volcanic tuff) are visible at Font de la Torre. This deposit contains juvenile pyroclasts and lithics (various millimetres in diameter), surrounded by a fine reddish-brown matrix. The black juvenile fragments are of basaltic composition with little vesiculation. The most plentiful lithics are red sandstone, although blue marls and pale grey calca- reous rock are also present. Although the deposit is fairly uniform in composition, different layers are visible and have been eroded - more effi- ciently at the boundaries between layers - and give the outcrop a terraced effect. This tuff appears along Riera de Canet Figure 110. Font de la Torre for about 3 km downstream from the spring and in places is 20-m thick. On Erosion by the streams (Riera de top of this fragmentary deposit lies a Canet, Torrent de Rocacorba and lava flow, which can be seen clearly on Torrent de Rissec) has created a series the left bank of Torrent de Rocacorba of deep pools that are unique in the and on the path that leads there. Catalan volcanic field.

Interpretation The presence of abundant lithic frag- racted with the magma and the resulting ments, along with a number of palaeo- explosions ejected a dense pyroclastic magnetic studies that have determined an flow that was channelled down the origi- emplacement temperature for these ma- nal valley of Riera de Canet. However, terials in excess of 550°C, are proof that successive pulses in this phase genera- this deposit is the product of the phreato- ted a series of sub-flows that gave rise to

magmatic eruption of Puig d'Adri. the incipient layers visible in this deposit. 3 l Furthermore, the elongated shape and Finally, a lava flow covered the deposited La Garrotxa Volcanic Zone channel-shaped cross-section suggest pyroclastic materials. Subsequently, the that a pyroclastic flow swept down and fi- water in the streams has eroded these lled in the former river valley. volcanic products and exposed the se- Thus, during the first phreatomagmatic quence of deposits (Fig. 111). phase an important amount of water inte-

Figure 111. Stages in the formation of the volcanic deposits at Font de la Torre.

89 3. Fitxes.enbaixa4/6/1207:17Página90

3 l La Garrotxa Volcanic Zone tomagmatic deposits. to examples of these phrea- best the contains Toscà d’en Sureda La in d'Adri crop out- The from Collsacarrera. road Canet the appear along cone the that form materials the and diameter in m 850 is ter truction. The tuff ring cra- tially cover this first cons- subsequent par- phases Strombolian from ting resul- - 3 - and 2 edifices cones cinder posed 1 edifice - formed was ring tuff the phase this during deposited; were cinder a and breccia of deal great and reatomagmatic ph- was and explosive highly first The five phases. had eruption This The eruption 5313 toCanetd’Adri GIV- the on right turn town, this after km 3 Gregori; Sant to GI-531 the along breccia deposits. Access from Girona is and surges pyroclastic of examples fine as La Sureda d’en Toscà, which exhibits known wood cork-oak Puig a stands d’Adri of flanks south-eastern the On Location andaccess 13 (Fig. 112) Access timeonfootl Activity typel Point ofinterestl pyroclastic surges Puig d’Adri: . Two superim- Phreatomagmatic (Fig. 112) Volcanic materialsintheToscà cork-oakwood 15 minutes Figure 112. . Schematic geological map of Puig d’Adri Puig of map geological Schematic 90 your left,theoutcropsbegin. 25 m to where, just behind the bank Can on about to for track right the along the Walk Toscà. to off a leads track where park Collsacarrera, before m 400 About Collsacarrera. of hamlet In the village, take the road towards the 3 l La Garrotxa Volcanic Zone 3 2 1 . These layers are thicker La Sureda d’en Toscà pyroclastic surge (3) Figure 113. and the fragments are looser. There is also degree of lamination often marked by the layers of ash. presence of The topmost layers of ash were deposited during the phreatomagmatic pulses and their lamination is due to the high energy present in the flow. These materials are pyroclastic surge deposits and their compaction of part deposited, were they when that, indicates condensed flow the in vapour water the and caused them to be compacted. The breccia crowning the sequence came from a series of less intense pul- phase. phreatomagmatic the in ses Finally, at the top there is a series of la- of series a is there top the at Finally, yers of pyroclastic breccia; the largest of the pyroclasts indicates that that same lithic fragments are present as in the ash 91 . (Fig. 113) . There are no layers (1) , which gives these layers a cer- (2) Interpretation Although not visible at this site, mate- ori- that scoria the beneath appear rials ginated from the eruption. This phreatomagmatic scoria, so Strombolian activity, signifies typical an inte- of rruption in the phreatomagmatic phase at the Scoriaceous materials are and cone start cinder a of part as found only normally of so their location in this the by outcrop, explained be only can vent, the from far eruption. the remobilisation of the scoria by later explosions. phreatomagmatic On close scrutiny and within just 20 metres of each other materials deposited in three groups in various layers can be observed The pyroclastic deposits of La Sureda d’en Toscà Sureda of La deposits pyroclastic The Description tain positive relief within the outcrop. The miniscule size of the fragments means that they cannot be identified with the naked eye. However, with the aid of a magnifying glass you can see that this ash contains a large proportion of lithic fragments of red sandstone and some marl. The marked lamination of the ash is obvious and the stratification is frequently crossed at a low dis- be can layers coarser few A angle. tinguished between the ash layers. At the base of the sequence lies a sco- a lies sequence the of base the At ria deposit formed almost entirely of juve- lapilli-sized vesicular highly black, nile fragments within this deposit, although at the top some angular lithics, mostly centime- various (of appear sandstone, of red diameter). in tres Covering the scoria are millimetric layers of ash with considerable compaction 3. Fitxes.en baixa 4/6/12 07:17 Página 91 Página 07:17 4/6/12 baixa Fitxes.en 3. 3. Fitxes.enbaixa4/6/1207:17Página92

3 l La Garrotxa Volcanic Zone Catalonia. in volcanoes spectacular most the of one as garded re- is Crosa La size, and ago. Due to its morphology years thousand hundred few a than more no ted this volcano was construc- that conservation of state excellent its from obvious is it old, years million two the volcanic rocks are over where Selva despite La in being and, unknown exact age of this volcano is The final phase. a Strombolian with phreatomagmatic, predominantly was eruption The rocks. Palaeozoic metamorphic and granite contacting by represented here system, and mountain Transversal the of end southern sediments, the and Pliocene Quaternary with filled Selva, La of pression de- the between boundary the on is lies volcano This La Crosa deSantDalmai Aiguaviva. through goes that (GI-533) Coloma Santa to road the take Girona, From Gironès. El and Selva La of regions the between border the on Dalmai Sant and Estanyol Aiguaviva, of settlements the between situated volcano a Dalmai, Sant de Crosa La from pyroclasts tract ex- to used Guilloteres Can of quarry The Location andaccess 14 Access timeonfootl Activity typel Point ofinterestl La Crosa deSantDalmai The morphologyof Phreatomagmatic View from CanGuilloteres quarry 5 minutes shape ofthisvolcano. area the see to flat difficult it make relatively a in lies it that fact the and ces edifi- its of height low The Figure 114. La Crosa de Sant Dalmai Dalmai Sant de Crosa La 92 crater ofLaCrosadeSantDalmai. the of view good a offers which roclasts, small a py- from formed climb high) 5-m (about mound can you road the from farthest part the In extracted. once were materials volcanic the where from area open an is there right the on along km 1 After crossing the road to Estanyol, about 1 3 l La Garrotxa Volcanic Zone (1) reveals Eruption sequence of (Fig. 114) Figure 115. La Crosa de Sant Dalmai (Fig. . The . . as being horseshoe-shaped. being as and abuts against the rim of the crater, which an aerial photo pine and holm oak woodland surrounds woodland oak holm and pine the depression. On its northern side, a low hill penetra- tes slightly inside the depression 93 (Fig. 115c) (Fig. 115d) . Currently, an artifi- When the volcanic activity had ceased, the crater filled with water, forming a lake that slowly began to silt up with lacustrine and colluvial sediments 115d) top of the northern edge of edge northern the of top the maar crater of this open edifice to is the south-east, possibly due to the emission of a small lava flow in the final stages eruption of the cial drainage system with two channels crossing the cone keep the crater dry. . (Fig. 115a) (Fig. , the diameter of (Fig. 115b) Interpretation The morphologies descri- vol- the to belong here bed canic edifices that constitute La Crosa vol- the of Analysis Dalmai. de Sant canic deposits and sediments reveals a series of the to rise gave that stages current relief features. The most important erup- the was volcano this of tion initial phase, which built phreatomagmatic a maar- type edifice with a large crater that initially much smaller was Description The view east from the top of the hill reveals a circular depression, this of bottom The some diameter. in m 1,250 depression (about 800 m wide) is flat level. ground original the below lies and It is currently used for crops and tree plantations. A line of hills covered in The morphology of the volcanic edifices volcanic of the morphology The As the explosions caused by the interaction of water and magma began to take place at greater depths the crater increased. The sliding of pyroclastic materials from the inside of the walls into the centre of the crater eventually made it far bigger. When the phreatomagmatic eruption Strombolian phase began ended that built a cinder cone on a 3. Fitxes.en baixa 4/6/12 07:17 Página 93 Página 07:17 4/6/12 baixa Fitxes.en 3. 3. Fitxes.enbaixa4/6/1207:17Página94

3 l La Garrotxa Volcanic Zone lw aeil i de to due is materials flow of emplacement the in asymmetry This metres. hundred few a only of ted ejec- were materials the village west the to while distant, km the 3.5 over Vilablareix, is today what beyond ched rea- dispersion the east, the Towards metrically. asym- distributed were which rock, country and fragments magma of re mixtu- a ejected plosions The phreatomagmatic ex- deposits are 30-m thick. west, the and high 200-m than the less is cone the though, In thick. 50-m over is materials fragmentary of layer the and Llop) Sant de (Turó south-west the to high m 203- is cone The crater. the around radially out spreads that dipping lax with deposits roclastic py- of sequence a of up made is cone Crosa's La La Crosa phreatomagmatic deposits park Dalmai, Sant of village the re the 10-km point on this road, just befo- At Aiguaviva. through (GI-533) Coloma Santa to road the take Girona, From Gironès. El and Selva La of regions Sant Dalmai on the border between the and Estanyol Aiguaviva, of villages the between lies Dalmai Sant de Crosa La Location andaccess 15 Access timeonfootl Activity typel Point ofinterestl La Crosa deSantDalmai Pyroclastic surgeandbrecciaof Phreatomagmatic Volcanic materialsinthequarryatCanCosta 5 minutes eet hn h meta- grani- and rocks morphic the than petent com- less are sector tern eas- the in found sediments Pliocene the ce, instan- for and, plosions) of the materials to the ex- (resistance subsoil the of competence varying the Figure 116. Schematic geological map of Puig d'Adri Puig of map geological Schematic 94 hr a rc has left heads track a where 400-m long and 20-m high. about are they as find to hard not are deposits Can volcanic The abandoned quarry. Costa the to trees hazel of field a through path a along wards north- m 200 about walk here From that direction. in ejected being products volcanic more to led also eastward vent the of bias the that ble possi- is it However, te. (Fig. 110) . 3 l La Garrotxa Volcanic Zone (Fig. 117, Stratigraphic Costa quarry was the product of a column from the Can Figure 117. In the third stage, the aquifer was re- layer 23) layer Strombolian phase occurring when the replenishing of the aquifer in stage 3 was insufficient to maintain the phreatomagmatic activity. 3. interac- of area the re-fed and plenished tion with the magma until enough there water to was produce a new pyroclastic surge. These three stages were repeated suc- and time of intervals short over cessively led to the build-up of the sequence of pyroclastic deposits exposed in outcrop. this The magma ascent was pro- bably continuous throughout the different phases and therefore the rechar- ging of the aquifer that interacted with the magma was rapid enough to maintain the phreatomagmatic eruption. It is likely that the scoria deposit morphic and rocks, are clearly igneous visible. The most plentiful lithics are granite, schist and porphyric deposits. The juvenile fragments show very little vesiculation, except for those in the scoria (layer 23), which are clearly more vesicular. The lithic fragments are angular and in some parts account for 60% of the deposit. 95 . . (Fig. (Fig. 117; e.g. layer 3) (Fig. 117; e.g. layer 2) ) and vary in thickness from just a few a just from thickness in vary and ) The aquifer was able to provide Less water was available in this stage this in available was water Less 117) Description At the end of this stage, there was almost no water left in the country rock. Interpretation La of phase phreatomagmatic the During Crosa de Sant Dalmai eruption a series of pulses occurred, each of which formed one or two layers of the sequence. The sequence of alternating breccia and ash was determined by the availability of water in the area of interaction with the magma. Three stages in the phreatomagmatic pulses can be separated: 1. enough water for optimal water-magma conside- a stage, first this In interaction. rable amount of water vaporised, gene- rating a pyroclastic surge that resulted in the ash deposit Up to 30 alternating layers of breccia and quarry the in exposed been have ash Quarrying at Can Costa at Can Quarrying centimetres to over a metre. centimetres At the base there is a layer over a metre thick, consisting mostly of large blocks of lithic fragments measuring 10 cm across (layer 1). On top lies a further series of la- me- fragments juvenile and lithic with yers asuring various centimetres across, and then ash (layers 2 to 22). Next, comes a metre-thick layer of scoria with sized lapilli- fragments (layer 23). Finally, more alternating layers of breccia and ash appear that are similar to the previous ones (levels 24 to 30), with at the base a breccia layer of 10-cm fragments. Thanks to the size of the fragments in the breccia, the difference between the juvenile clasts, which are black basalt, and the lithics originating from different meta- 2. and so the water-magma lower; as a ratio result, the was explosion was pyroclas- a generated and effective less deposit breccia tic 3. Fitxes.en baixa 4/6/12 07:17 Página 95 Página 07:17 4/6/12 baixa Fitxes.en 3. 3. Fitxes.en baixa 4/6/12 07:17 Página 96 Glossary l1l Volcanoes l3 l La Garrotxa Vo l c a n i c Aquifer Petrogenic process Zone. Sites of volcanic A water-bearing permeable geolo- Any of the processes that arise du- interest gical formation in which groundwa- ring the formation of a rock. ter is stored and through which Petrology Eocene water can flow. A branch of geology that deals with The second epoch of the Lower the origin, history, occurrence, Tertiary, lasting from 56.5 to 35.4 Country rock Ma. The rock surrounding the intrusion structure, chemical composition of another rock in the form of a and classification of rocks. Formation seam, dyke, sill or pluton. Pluton A unit of lithostratigraphy establis- A large body of intrusive igneous hed in accordance with lithological Crystal character. A solid substance of defined che- rock formed from magma cooling mical composition, made up of under the Earth's surface. Banyoles Formation atoms or molecules arranged in a Sedimentary rock An Eocene unit made up of regular and periodic pattern in a A type of rock formed by the accu- bluish marls. space that, in favourable condi- mulation of material (e.g. minerals Bellmunt Formation tions, may give flat surfaces known or organic rock) on the Earth's sur- An Eocene unit mostly made up as faces. face within bodies of water. of clay, silt, marl, sandstone and Dome Silicate mineral red conglomerate. A mound-shaped protrusion with A mineral formed of SiO4 tetrahe- Bracons Formation steep flanks produced by an erup- dra. An Eocene unit made up marl, tion of highly viscous, gas-poor Sill sandstone and conglomerate magma, gradually expelled from rocks. the vent. A body of igneous rock that intru- des between older rock layers. Folgueroles Formation Dyke Texture of rock An Eocene unit made up of A type of sheet intrusion of igneous sandstone. rocks that cut discordantly across Also known as microstructure, rock adjacent rock following existing texture refers to the relationship fractures, which are generally verti- between the constituent minerals cal and measure tens to hundreds and vitreous material of an endo- of metres in thickness. genous or sedimentary rock. Geochemistry The science that studies the abundance and distribution of the solid l2l Volcanism in matter of the Earth or a celestial Catalonia body, and its composition Igneous rock Alkaline rock Rock formed by the solidification of Magmatic rock in which the so- magma in or outside the lithosphe- dium oxide (Na2O) and potassium re. oxide (K2O) combined are present in a greater percentage than the Isotope aluminium oxide (Al2O3). One of two or more species of atoms of a chemical element that Calc-alkaline magma have the same atomic number (the Magma with a SiO2 content betwe- same number of protons), but a en 55% and 61% and more so- different number of neutrons. dium and potassium oxide than calcium oxide. Joint A fracture in a rock with no relative Feldspathoid displacement of any part, the sur- Feldspathoids are a group of tec- face of which is usually flat and dif- tosilicate minerals made up of fers greatly from the stratification. SiO2, Na, K, Ca and Li that appear in place of feldspar when the Lithostatic pressure magma is poor in SiO2. Vertical stress imposed on a layer of soil or rock by the weight of Neogene-Quaternary overlying material. The time period between 23 Ma and the present. Metamorphic rocks Rock formed from pre-existing rock Rare earth element that, with no intermediate liquid Rare earth elements or metals are stage, has been transformed mine- a group of chemical elements that ralogically and structurally in res- include the lanthanides plus scan- ponse to changes in physiochemi- dium and yttrium. cal conditions, temperature, pressure or shearing stresses.

97 Bibliography

Specialised bibliography Araña, V. [et al.], “El volcanismo Mallarach, J.M., Carta geològica de Pallí, Ll.; Roqué, C., El vulcanisme neógenocuaternario de Cataluña: la regió volcànica d'Olot: Litologia i de les comarques gironines (III-Alt i caracteres estructurales, geomorfologia=Geological map... Baix Empordà). [Map]. Girona: petrológicos y geodinámicos”, A c t a [Map]. E.1:20.000. Olot: City Girona Provincial Council; Geológica Hispánica, [University of Council, 1982. Universidad de Girona, 1996. Barcelona; Jaume Almera Institute of Earth Sciences], vol. 18 (1983), no. Mallarach, J.M., El vulcanisme Pallí, Ll.; Roqué, C.,“Els afloraments prehistòric de Catalunya. Girona: volcànics a les comarques 1, pp. 1-17. Girona Provincial Council, 1998. gironines”, Revista de Girona, Cas, R.A.F.; Wright, J.V. Volcanic 322 pp. Girona Provincial Council, vol. 174 Successions: Modern and Ancient. Martí, J.; Araña, V., La volcanología (1996b), pp. 65-68. London: Chapman & Hall, 1987. actual. Madrid: Spanish National Planagumà i Guàrdia, Ll.; “El 521 pp. Research Council (CSIC), 1993. vulcanisme freatomagmàtic de la Donville, B., Géologie Néogène et 578 pp. (Nuevas Tendencias ; 21). serra del Corb”, The Volcanic âges des éruptions volcaniques de Region of La Garrotxa Natural Park la Catalogne orientale, Toulouse Martí, J., “El vulcanisme (PNZVG), 1995. [Paul Sabatier University], 1973. 3 neogenoquaternari dels Països volumes. Note: unpublished Catalans”, in Història natural dels Pujadas, A.; Mallarach, J.M., “El doctoral thesis. Països Catalans: Geologia. vulcanisme de la Vall de Llémena”, Barcelona: Catalan Encyclopaedia Revista de Girona, Girona Provincial Ferrés i López, D., “Caracterització Foundation, 1992,vol. II, pp. 360- Council, vol. 174 (1996), pp. 77-81. de l’activitat estromboliana a la ZVG: 371. Pujadas, A., El vulcanisme de la Caracterització del volcà Martí, J. [et al.], “Projecte de Vall de Llémena. Girona: University Croscat”,The Volcanic Region of La geologia de la zona volcànica of Girona, 1997. vol. 5, 67 pp. Garrotxa Natural Park (PNZVG), catalana: Informe final 1996”, (Dialogant amb les Pedres ; 5). 1995. Barcelona, Jaume Almera Institute Ferrés, D.; Planagumà, Ll.; of Earth Sciences of the Spanish Pujadas, A.; Pallí, L., “Fosa de Pujadas, A. [et al.], “Els nous National Research Council (CSIC), Olot”. In Pallí, L. and Roqué, C. volcans del Parc Natural de la Zona 1996. Note: unpublished. (ed.). Avances en el estudio del Volcànica de la Garrotxa”, Revista de Cuaternario español, Girona, Girona, Girona Provincial Council, Martí, J.; Mallarach, J.M., (1999), pp. 346-356. vol. 188 (1998), pp. 32-41. “Erupciones hidromagmáticas en el Ros, X.; Palomar, J.; Gaete, R., volcanismo cuaternario de Olot “Estudi geotècnic del cingle de Francis, P., Volcanoes: A planetary (Girona)”, Estudios Geológicos, Castellfollit de la Roca”,The Volcanic perspective. USA: Clarendon Press, [s.n.], vol. 43 (1987), pp. 31-40. Region of La Garrotxa Natural Park 1995. 443 pp. Martí, J. [et al.], “Cenozoic (PNZVG), 1996. Guerin, G.; Benhamou, G.; magmatism of the Valencia trough Mallarach, J.M., “Un exemple de (western Mediterranean): Saula, E.; Picart, J.; Mató, E. [et fusió parcial en medi continental: El relationship between structural a l . ] , “Evolución geodinámica de la vulcanisme quaternari de evolution and volcanism”, fosa del Empordà y las sierras Catalunya”, Vitrina: publicació del Tectonophysics, [Elsevier Science transversales”, Acta Geológica Museu Comarcal de la Garrotxa, La Publishers], vol. 203 (1992), pp. Hispánica, University of Barcelona; Garrotxa Regional Museum, vol. 1 145-165. Jaume Almera Institute of Earth (1985), pp. 19-26. Sciences, vol. 29 (1996), pp. 55-75. Martí, J. [et al.], “Mecanismos Sheridan, M. F.; Wohletz, K. H., López-Ruiz, J. ; Rodríguez- eruptivos del volcán de la Closa de “Hydro-volcanism: Basic Badiola, E., “La región volcánica Sant Dalmai (Girona)”, Anales de considerations and review”, Journal Mio-pleistocena del NE de España”, física, Series B (special edition); pp. of Volcanology and Geothermal Estudios Geológicos, [s.n.], vol. 41 143-153. Research, [Elsevier Science (1985), pp. 105-126. Neumann, E. R. [et al.], “Origin and Publishers B.V.], vol. 17 (1983), pp. Lewis, C. J.; Baldrige, W. S.; implications of mafic xenolits 1-29. Asmeron, Y., “Neogene associated with Cenozoic extension- asthenosphere-derived volcanism related volcanism in the Va l è n c i a Tournon, J., “Les roches and NE-directed extension in NE Trough, NE Spain”, Mineralogy and basaltiques de la province de Spain: Constraints on the Petrology, [ S p r i n g e r- Verlag], vol. 65 Gerona (Espagne); basanites à geodynamic evolution of the (1999), pp. 113-139. leucite et basanites à analcime”, western Mediterranean”, Eos Trans. Bull. Soc. Fr. Minéral. Cristallogr., AGU, 79 (17), Spring Meeting Pallí, Ll.; Roqué, C., El vulcanisme [s.n], vol. 92 (1969), pp. 376-382. Supplement, S 336-S 337, 1998. de les comarques gironines (II- Ziegler P.A., “European Cenozoic Gironès). [Map]. Girona: Girona rift system”, Tectonophysics, Mallarach, J.M.; Martí, J.; Claudin, Provincial Council; University of [Elsevier Science Publishers], vol. F ., “Primeres aportacions sobre el Girona, 1995. vulcanisme explosiu d'Olot”, R e v i s t a 208 (1992), pp. 91-111. de Girona, Girona Provincial Council, vol. 121 (1987), pp. 69-74.

98 Basic recommended reading Garrotxa Catalonia Aragonès Valls, Enric. Descobrint el Oliver Martínez-Fornés, Xavier. El Arbat, Sílvia; Rigau, Eva; Solé, vulcanisme quaternari a la Garrotxa: Parc Natural de la Zona Volcànica Lluís, Carícia de volcà [Girona]: de les observacions precientífiques de la Garrotxa. Olot: Llibres de Bescanó Council, Vilobí Council, als primers estudis geològics (S. Batet, DL 2002. 72 pp. (Guies dels 1991. 94 pp. XVI-XIX). [Barcelona]: Council. Llibres de Batet ; 11) “Dossier: El vulcanisme gironí”, Culture Institute, 2001. pp [77]-125. Prats, Josep M. El Parc natural de Revista de Girona. Girona: Girona Bassols Isamat, Emili, “Els volcans la zona volcànica de la Garrotxa Provincial Council,1996 XLII Year, salvats”, Revista de Girona no. 251, [map-guide]. Barcelona: Generalitat no. 174 (genuary-february 1996), 2008, pp 60-65. of Catalonia., The Volcanic Region PP. 58-93 of La Garrotxa Natural Park 1994. GeoVirtual, SL, Volcans en 3D: vol 24 pp + 1 map-guide. Mallarach i Carrera, Josep Maria. virtual pel Parc natural de la Zona El Vulcanisme prehistòric de Volcànica de la Garrotxa. [S.l.]: Planagumà Guàrdia, Llorenç. Catalunya. Olot: Alzamora, 1998. Generalitat of Catalonia. The Coneixem el que trepitgem?: el 322pàg. Volcanic Region of La Garrotxa patrimoni geològic de la Pallí i Buxó, Lluís; Roqué i Pau, Natural Park, [2008]. Garrotxa.Olot: Museum of Carles. El vulcanisme de les Cartographic Institute of Catalonia; Volcanoes: Culture Institute of Olot comarques gironines [cartographic Geological Institute of Catalonia; city, DL. 2005. 36pp. + 1 optical document]. [Girona]: Provincial The Volcanic Region of La disc (CD-ROM) Council; Girona University. Area of Garrotxa Natural Park. Carta TOSCA, Equip d'Educació Geodynamics, DL 2007. 4 maps: vulcanològica de la zona volcànica Ambiental, “Estratègia per a la col.; 57 x 70cm. de la Garrotxa [cartographic gestió del vulcanisme al Parc document], Barcelona: Cartographic Natural de la Zona Volcànica de la Pallí i Buxó, Lluís; Roqué i Pau, Institute of Catalonia, 2007 Garrotxa”, The Volcanic Region of Carles. El Patrimoni geològic de les La Garrotxa Natural Park (PNZVG), terres gironines: 300 elements Mallarach i Carrera, J. M.; Riera i 2000. 47pp. singulars. Girona: Universitat de Tussell, M., Els volcans olotins i el Girona. Àrea de Geodinàmica seu paisatge: iniciació a la seva Externa, 2009. 425pàg. coneixença segons nou itineraris Pujadas, Albert [et al.]. El pedagògics. Barcelona: vulcanisme de la Vall de Serpa,1981. 250 pp. Llémena.Girona: Universitat de Mallarach i Carrera, J. M., Els Girona. Àrea de Geodinàmica, Volcans. Girona Provincial Council. 1997. 54pàg. (Dialogant amb les Caixa de Girona,1989 (Revista de pedres ; 5) Girona logbook ; 21). Pujadas, Albert [et al.]. El Martí, J. [et al.], El vulcanisme: guia vulcanisme de La Selva. Girona: de camp de la zona volcànica de la Girona University. Area of Garrotxa, 2nd edition. Olot: The Geodynamics, 2000. 50pp Volcanic Region of La Garrotxa (Dialogant amb les pedres ; 8) Natural Park, 2001. 322 pp Martí, J. [et al.], “Complex interaction between Strombolian an phreatomagmatic eruptions in the Quaternary monogenetic volcanism of the Catalan Volcanic Zone (NE of Spain)”, Journal of Volcanology and Geothermal Research, Elsevier Scientific Publishing Company, vol. 201, issues 1-4, (Abril 2011), pp. 178-193 Museu dels Volcans. [Guide]. Olot: Comarcal Museum of la Garrotxa; Caixa de Girona,1993. [24] pp. Neovídeo. Els volcans de la Garrotxa [video recording]. Olot, The Volcanic Region of La Garrotxa Natural Park (PNZVG), 1996. 1 videotape (14 min.), colour (VHS), sound BS.

99 La Garrotxa Volcanic Zone Natural Park publications Books and unpublished Booklets documents L’Agricultura i la ramaderia al Parc The Volcanic Region of La Itineraris pedestres: Sender Joan Natural de la Zona Volcànica de la Garrotxa Natural Park, Pla especial Maragall (la Fageda d’en Jordà). Garrotxa. Olot: generalitat of de La Zona Volcànica de La Olot: Generalitat of Catalonia. The Catalonia. The Volcanic Region of La Garrotxa: Aprovació definitiva, Acord Volcanic Region of La Garrotxa Garrotxa Natural Park, 2011. 37pp GOV/161/2010, de 14 de Natural Park, 1995. No. 2. Parc Natural de la Zona Volcànica setembre, pel qual s’aprova Itineraris pedestres: Olot; fageda de la Garrotxa = Parque Natural de definitivament El Pla Especial de La d’en Jordà; Can Xel. Olot: la Zona Volcánica de la Garrotxa = Zona Volcànica de La Garrotxa, Generalitat of Catonia. The Volcanic Parc naturel de la Zone volcanique Barcelona: Generalitat of Catalonia, Region of La Garrotxa Natural Park, de La Garrotxa = The Volcanic [2010]. 5 vol. And optical disc 1995. No. 3. Region of La Garrotxa Natural Prats Santaflorentina, Josep M.; Park.2nd ed. Barcelona: Generalitat Planagumà, Llorenç; Oliver, Xavier. Itineraris pedestres: Santa Pau; of Catalonia. Natural Parks Service, Entre volcans. [Olot]: Generalitat of volcà de Santa Margarida; Can Xel . 2008. [10]pp. Catalonia. The Volcanic Region of La Olot: Generalitat of Catalonia. The Garrotxa Natural Park, 2007. 141pp. Volcanic Region of La Garrotxa Natural Park, 1995. No. 4. Postcards and bookmarks RCR Aranda, Pigem, Vilalta Itineraris pedestres: cingleres de [Postcards]: Materials volcànics, A r q u i t e c t e s . Les cases que no Castellfollit. Olot: Generalitat of Volcà del Croscat, Fageda d'en criden = Las casas silenciosas = Catalonia. The Volcanic Region of Jordà, Volcà Montsacopa, Tranquil houses: La casa de pagès al La Garrotxa Natural Park; Castellfollit Castellfollit de la Roca. [Olot]: Parc Natural de la Zona Volcànica de Council, 1996. No. 13. Generalitat of Catalonia. The la Garrotxa. Olot: Generalitat of Catalonia. The Volcanic Region of La Itineraris pedestres: grederes del Volcanic Region of La Garrotxa Garrotxa Natural Park, 2011. 118pp. volcà del Croscat. Olot: Generalitat of Natural Park, 2002. La recerca científica al Parc Natural Catalonia. The Volcanic Region of La [Bookmarks] Centre de de la Zona Volcànica de la Garrotxa: Garrotxa Natural Park, 1995. No. 15. Documentació = Centro de 1 9 8 2 - 1 9 9 2. Olot: Generalitat of Itineraris pedestres: ruta de les Tres Documentación = Documentation Catalonia. The Volcanic Region of La Colades. El Boscarró, el Molí Fondo Centre. Olot: Generalitat of Catalonia. Garrotxa Natural Park, 1993. 146pp. i Fontfreda. Olot: Generalitat of The Volcanic Region of La Garrotxa Catalonia; Sant. Joan les Fonts Natural Park, 2009 and 2011 Un Parc de contes: rondalles Council, 1997. No. 16. Volcans de la Garrotxa [Gràfic]. escrites pels estudiants de primària [Olot]: Generalitat of Catalonia. The de la Garrotxa per ser llegides i Itineraris pedestres: volcà del Volcanic Region of La Garrotxa escoltades vora dels volcans. Olot: Montsacopa. Olot: Generalitat of Natural Park, [2011]. [36] Generalitat de Catalunya. The Catonia.; IMPC, 1997. No. 17. bookmarks; maps; 6 x 21 cm Volcanic Region of La Garrotxa Itineraris pedestres: Sant Feliu de Natural Park, 2009. 111pp. Pallerols, itinerari urbà. Sant Feliu de Posters Pallerols,1999. No.18. Leaflets El vulcanisme estrombolià de la El Centre de Conservació de Itineraris pedestres: valls de Sant Garrotxa. Olot: The Volcanic Region Plantes Cultivades de Can Jordà . Iscle i del Vallac: volcans i castells. of La Garrotxa Natural Park Barcelona: Generalitat of Catalonia. Sant Feliu de Pallerols,1998. No.19. (PNZVG), 1991. The Volcanic Region of La Garrotxa Oferta pedagògica del Parc Natural L’arquitectura del volcànic. Olot: Natural Park, [2006]. de la Zona Volcànica de la The Volcanic Region of La Garrotxa Garrotxa: curs 2011-2012. Olot, Natural Park (PNZVG), 1995. Centre de Documentació = Centro de Documentación = The Volcanic Region of La Garrotxa El Parc Natural de la Zona Volcànica Documentation Centre. Olot: Natural Park (PNZVG), 2011. Maps de la Garrotxa (panoramic). Olot: Generalitat of Catalonia. The The Volcanic Region of La Garrotxa Volcanic Region of La Garrotxa Maps Natural Park (PNZVG), 1997. Natural Park, 2011. Cartographic Institute of Catalonia; 12 indrets d'interès per visitar al The Volcanic Region of La Video/DVD parc: Parc Natural de la Zona Garrotxa Natural Park; Carta GeoVirtual, SL, Volcans en 3D: vol Volcànica de la Garrotxa. [Olot]: vulcanològica de La zona volcància virtual pel Parc natural de la Zona Generalitat of Catalonia. The de La Garrotxa. Barcelona. Volcànica de la Garrotxa. [S.l.]: Volcanic Region of La Garrotxa Cartographic Institute of Catalonia; Generalitat of Catalonia. The Natural Park, [2007]. 1 leaflet, map; Gological Institut of Catalonia, 2007 Volcanic Region of La Garrotxa 42x42 cm. Municipi de Sant Feliu de Pallerols: Natural Park, [2008]. map-guide [Olot] Generalitat of Itineraris pedestres: fageda d’en Catalonia. The Volcanic Region of La Jordà; volcà de Santa Margarida; volcà del Croscat. Olot: Generalitat of Garrotxa Natural Park, [1998-2001] Catalonia. The Volcanic Region of La Garrotxa Natural Park, 1996.No. 1.

100 Map of the Services in La Garrotxa Volcanic Zone Natural Park

Natural Park Natural Park Information Centre Toilets Natural Reserve Car- park Picnic area Built-up area Signposted walking itinerary Viewpoint Documentation Centre Museum Environmental Education Organisation

101 101 Services accredited by La Garrotxa Volcanic Zone Natural Park

The entities that collaborate with La Garrotxa Volcanic Zone Natural Park are largely small businesses or groups of businesses that mainly work in the sector of environmental and cultural education in the Park. They are characterized by their commitment to providing quality services and their active collaboration with the Park in ensuring the successful protection and improvement of its natural values and the sustainable exploitation of its resources

This quality service consists of: • Discovery activities, knowledge of the environment and research in and around the Park’s centres of interest. • Interdisciplinary work in various fields of study (essentially the environment and social relationships). • Activities with a maximum of 20 participants per guide/teacher • Guide/teachers with excellent knowledge of the local region and all accredited as guides by La Garrotxa Volcanic Zone Natural Park. • Continual in-service training • Main area of operation in the Natural Park • All services covered by third-party insurance • Teaching material provided to be used by teachers before and after visits to Park • Active participation in scientific research and the protection of the natural and cultural values of the region

VERD VOLCÀNIC La Garrotxa Association for Environmental and Cultural Education Secretary: Description Beth Cobo Created in 2003, Verd Volcànic aims to improve the c/ Antoni Llopis, 6 1r 5a quality of the services offered by the companies in the 17800 Olot association: to stabilise the educational team, provide Tel. (+34) 972 90 38 22 team members with training in the various knowledge (+34) 657 861 805 areas and work to improve continually the serv i c e s Fax (+34) 972 27 32 28 e-mail: provided. It also undertakes to develop its activity in a i n f o @ v e r d v o l c a n i c . c a t way which is consistent with the region's conserv a - Web page: tion and to ensure the protection of its natural and w w w. v e r d v o l c a n i c . c a t cultural values. Services provided • Guided visits in Catalan, Spanish, English and French. • Diagnostic surveys of local natural and cultural heritage • Creation of tourist packages • Studies of flora and fauna • Design of footpath networks • Environmental and cultural technical assessment • International cooperation projects • Activities for school groups from half day to five- day stays • Study programmes for schoolchildren from countries such as Great Britain and Eire.

102 102 LA CUPP, SCCL Secretary: Description Ester Morchón An environmental education cooperative created in Avda. República 2006 formed by a team of graduates in Dominicana 3, bajos Environmental Sciences, Psychology and 17800 Olot Geography with extensive experience in the field of Tel. (+34) 972 27 32 23 environmental education. Fax (+34) 972 26 22 33 e-mail: Services [email protected] • Environmental activities in La Garrotxa Vo l c a n i c Zone Natural Park for schoolchildren of all ages • Environmental activities for adults including guided walks to some of the Natural Park’s best known sites (volcanoes of Croscat and Santa Margarida, Fageda d’en Jordà beechwood), but also to some of its least known treasures (Sant Joan les Fonts lava flows, Colltort Castle, chur- ches of La Serra del Corb) • Languages: all the above activities can be carried out in Catalan, Spanish, English, German or French • Technical work including studies in the fields of tourism and education, coordination of training and education programmes.

T O S C A E n v i ronmental services in education and tourism

Secretary: Description Octavi Bonet TOSCA is a services company working to improve Mas Tarut the region through: education, communication, in- Av. de Santa Coloma, s/n terpretation and socio-environmental information, 17800 Olot the drawing up of technical studies and developing Tel. (+34) 972 27 00 86 environmental action in La Garrotxa. TOSCA con- Fax (+34) 972 27 04 55 e-mail: sists of a team of 10 professionals with back- [email protected] grounds in Geology, Biology, Education and To u r i s m Web page: with extensive experience in environmental matters. www.tosca.cat Opening hours: Services 9-14 h i 16-18 h • Management of the Educational and Information Services of The Volcanic Region of La Garrotxa Natural Park. • Development of educational activities and guided walks adapted to educational level. Preparation of teaching materials. • Training programmes for teachers, environmental educators, students, and so on. • Drawing up of studies on environmental education in protected natural areas. • Design of geotourism trails. • Recovery of volcanic heritage. • Participation in projects on sustainability, agrobio- diversity, sustainable tourism, studies of vulnera- ble areas, recovery of natural areas, and so on. • Contributions to publications on environmental education and sustainability.

103 103 Notes

104 104 105 Recommendations and indications for visitors to the La Garrotxa Volcanic Zone Natural Park

The Park has an extensive network of The maintenance service has to work signposted itineraries that reach some hard to keep the most frequented of the most interesting sites in the re- areas clean. Please use the bins or gion. take your rubbish home with you.

The Natural Park consists mostly of The capture and collection of animals, private property. Please ensure that rock and mineral specimens and you do not disturb residents. plants is forbidden in the Natural Park.

Camping is forbidden within the Park. In a number of clearly signposted Nevertheless, there are numerous areas access is limited to park servi- camp sites, hotels and hostels in the ces and residents. Vehicle access Park where visitors can stay. here is forbidden. .

For reasons of safety and conserva- The Park information centres give spe- tion, the lighting of fires is strictly prohi- cial permits for those with reduced bited. mobility in order to visit restricted areas by car.

106 Natural Park Services

Information Centres Educational Services Casal dels Volcans Casal dels volcans Av. de Santa Coloma, s/n Av. de Santa Coloma, s/n 17800 Olot 17800 Olot Tel. (+34) 972 26 81 12 Information and bookings: Fax (+34) 972 27 04 55 weekdays 9.00 am to 2:00 pm [email protected] and 4.00 to 6.00 pm Can Serra Tel. (+34) 972 27 00 86 Fageda d’en Jordà (+34) 972 26 81 12 [email protected] Can Passavent Croscat Volcano Web Pages General information: Documentation Centre www.gencat.cat/parcs/garrotxa Opening hours: weekdays 9.00 am to 2.00 pm. Documentation Centre Visits by appointment only. catalogue query: Tel. (+34) 972 26 46 66 http://beg.gencat.net/ Fax (+34) 972 26 55 67 [email protected]

ISBN 978-84-393-8852-4

9 788439 388524

Generalitat de Catalunya Departament d’Agricultura, Ramaderia, Pesca, Alimentació i Medi Natural