Geophysics of the Canary Islands Results of Spain’s Exclusive Economic Zone Program Edited by Peter Clift and Juan Acosta Reprinted from Marine Geophysical Researches, Volume 24, Nos. 1-2, 2003. Library of Congress Cataloging-in-Publication Data A. C.I.P. Catalogue record for this book is available from the Library of Congress ISBN 1-4020-3325-7 Published by Springer, P.O. Box 17, 3300 AA Dordrecht, The Netherlands. Sold and distributed in the U.S.A. and Canada by Springer, 101 Philip Drive, Norwell, MA 02061, U.S.A. In all other countries, sold and distributed by Springer, P.O. Box 17, 3300 AH Dordrecht, The Netherlands. Printed on acid-free paper All Rights Reserved (cid:2) Springer 2005 No part of the material protected by this copyright notice may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording or by any information storage and retrieval system, without written permissionfrom the copyright owner. Printed in the Netherlands Table of Contents Foreword v–vi J. ACOSTA, E. UCHUPI, A. MUN˜ OZ, P. HERRANZ, C. PALOMO, M. BALLES- TEROSandZEEWorkingGroup/GeologicevolutionoftheCanarianIslandsof Lanzarote, Fuerteventura, Gran Canaria and La Gomera and comparison of landslidesattheseislandswiththoseatTenerife,LaPalmaandElHierro 1–40 J. ACOSTA, E. UCHUPI, A. MUN˜ OZ, P. HERRANZ, C. PALOMO, M. BALLES- TEROSandZEEWorkingGroup/SaltDiapirs,SaltBrineSeeps,Pockmarksand SurficialSedimentCreepandSlidesintheCanaryChanneloffNWAfrica 41–57 J. ACOSTA, E. UCHUPI, D. SMITH, A. MUN˜ OZ, P. HERRANZ, C. PALOMO, P. LLANES, M. BALLESTEROS and ZEE Working Group / Comparison of volcanic rifts on La Palma and EI Hierro, Canary Islands and the Island of Hawaii 59–90 P. LLANES, A. MUN˜ OZ, A. MUN˜ OZ-MARTI´N, J. ACOSTA, P. HERRANZ, A. CARBO´ , C. PALOMO and ZEE Working Group / Morphological and structural analysis in the Anaga offshore massif, Canary Islands: fractures and debris avalanches relationships 91–112 A. CARBO´ , A. MUN˜ OZ-MARTI´N, P. LLANES, J. A´ LVAREZ and EEZ Working Group / Gravity analysis offshore the Canary Islands from a systematic survey 113–127 M. CATALA´ N, J. MARTI´N DAVILA and ZEE Working Group / A magnetic anomaly study offshore the Canary Archipelago 129–148 L.I. GONZALEZ DE VALLEJO, R. CAPOTE, L. CABRERA, J.M. INSUA and J. ACOSTA / Paleoearthquake evidence in Tenerife (Canary Islands) and pos- sible seismotectonic sources 149–160 E. ANCOCHEA and M.J. HUERTAS / Age and composition of the Amanay Seamount, Canary Islands 161–169 DigitalTerrainModeloftheCanaryIslandsEEZ.CourtesyofMultibeamMapingGroup,InstitutoEspan˜oldeOceanografia,Madrid, Spain. Foreword of the Director of the Oceanographic Spanish Institute The eight papers contained in this special MGR issue reflect partly the successful collaboration betweenagroupofinstitutionsandresearchersworkingonamajorresearchprogramsince1995: the Spanish EEZ Program (Exclusive Economic Zone Program). TheSpanishEEZprogramwassetupin1995afterapoliticalmandateoftheSpanishgovernment to prepare a full study - comprising hydrography, geology, geophysics and oceanography- of the Spanish EEZ. Leaders of the study were the Instituto Espahol de Oceanografia (IEO) and the Instituto Hidrogra´fico de la Marina (IHM). Since its beginning, the program disposed one month per year on the use of the R/V Hespe´rides and other Spanish oceanographic research ships like the R/V Cornide de Saavedra, the Vizconde de Eza and the Tofin˜o. Other research groups, universities and private companies also have collaborated in the sea- cruises. Present special issue shows the first scientific results of the EEZ Program in the Canary Islands area. Moreover, due to its scientific quality, the Program could be considered as an example of cooperation between different institutions, teams and individuals working on the same project. Finally, the IEO, which supports part of the program, should express its deep gratitude to all captains, crews and technicians of the different oceanographic vessels that participated in the research campaigns. Their work made this issue possible. Concepcio´n Soto Directora del IEO Foreword of the Director of the Hydrographic Marine Institute Article 132.2 of the Constitutional Law sets the grounds for public property of the natural resources of the Spanish Exclusive Economic Zone (ZEE for its Spanish acronym), implying the sovereign right to explore, exploit, conserve and administer all living and non-living resources coming from the sea-bed and the adjacent waters of the maritime area that goes from the end of the territorial sea to a distance of two hundred sea miles, counting from the base line from where its width is measured. According to the agreement of the Council of Ministers of April 23rd, 1993, the Ministry of Defence is authorized to use the BIO ‘‘Hespe´rides’’ to carry-out research campaigns for data gathering during one month per year. The Hydrographical and Oceanographic Research Plan of the Spanish Exclusive Economic Zone (ZEE)wasapprovedbyMinisterialOrder55/1994ofMay30th,amplifiedbytheMinisterialOrder 94/1993 of September 21st, in which the FAS Cartographic Plan was approved. OnMay25thof1994,theframeworkcooperationagreementbetweentheMinistryofDefenceand the Spanish Oceanographic Institute (IEO for its Spanish acronym) concerning Hydrographical and Oceanographic Research on the ZEEE was approved. This Framework Agreement assigns the hydrography of the area to the Marine Hydrographic Institute, using the multi-beam sounding devices installed onthe BIO ‘‘Hespe´rides’’; and thedata gathering that leads to a better knowledge of the physical structures of the seabeds to the IEO. During the years 95, 96 and 97 data gathering has been carried-out on the Balearic Islands and duringtheyears98,99and2000ontheCanaryIslandswithcampaignheadscomingalternatively from IHM and IEO personnel. The results of the various campaigns were extraordinaire, especially because of the very close collaboration between the participating Institutions, more specific with the IEO, a collaboration ofwhichtheresultsclearlycanbeseeninthisscientificworkabouttheCanaryArchipelagoandin future joint works that surely will be carried-out CN. D. Fernando Quiro´ s Cebria´ Director del Instituto Hidrogra´fico de la Marina MarineGeophysicalResearches (2003) 24: 1–40 ©Springer2005 10.1007/s11001-004-1513-3 Geologic evolution of the Canarian Islands of Lanzarote, Fuerteventura, Gran Canaria and La Gomera and comparison of landslides at these islands with those at Tenerife, La Palma and El Hierro J.Acosta1,∗,E.Uchupi2,A.Muñoz1,P.Herranz1,C.Palomo1,M.Ballesteros1 &ZEEWorking Group3 1InstitutoEspañoldeOceanograf´ıa.GrupodeCartograf´ıaMultihaz.Corazo´ndeMar´ıa,8,28002Madrid 2WoodsHoleOceanographicInstitution,WoodsHole,MA02543,USA 3A.Carbo´, A.Muñoz-Mart´ın, Univ.Complutense, Madrid; J.Mart´ın-Da´vila, M.Catala´nandJ.A.Mar´ın, RealOb- servatorio de la Armada. S.Fernando, Ca´diz; F.Pe´rez-Carrillo, C. Mate´, Instituto Hidrogra´fico de la Marina. Ca´diz. ∗ Correspondingauthor(E-mail:[email protected]) Keywords:multibeammapping,CanaryIsland,avalanches,geomorphology Abstract InthispaperwediscusstheresultsofaswathbathymetricinvestigationoftheCanaryarchipelagooffshorearea. Thesenewdataindicatethatvolcanismispervasivethroughouttheseafloorintheregion, muchmorethatwould be suggested by the islands. We have mapped tens of volcanic edifices between Fuerteventura and Gran Canaria andoffshoreTenerife, LaGomera, ElHierroandLaPalma. VolcanicflowsarepresentbetweenTenerifeandLa Gomera and salic necks dominate the eastern insular slope of La Gomera. This bathymetry also supports land geologic studies that indicate that the oceanic archipelago has acquired its present morphology in part by mass wasting,aconsequenceofthecollapseofthevolcanicedifices.Intheyoungerislands,Tenerife,LaPalmaandEl Hierro,theQuaternary(1.2to0.15Ma)debrisavalanchesarereadilyrecognizableandcanbetracedoffshorefor distancesmeasuredintensofkm. Offtheolderislands, Lanzarote, Fuerteventura, GranCanariaandLaGomera (<20to3.5Ma),theavalancheshavebeenobscuredbysubsequentturbiditycurrentdepositionanderosionaswell ashemipelagicprocesses.ThefailureoffshorewesternLanzaroteisintheformofarampatthebaseoftheinsular slopeboundontheseawardsidebyascarp. Itssizeandthelackofevidenceofrotationalongitslandwardsside precludesthepossibilitythatitisaslump.Itprobablyrepresentsaslidewhoseouterscarpiscausedbybreak-up oftheslide. Moundsontheramp’ssurfacemayrepresentpost-displacementvolcanicstructuresorexoticblocks transported to their present locations by the slide. The failures offshore Fuerteventura are so large that, although theyoccurredintheMiocene-Pliocene, exoticblocksdisplacedfromupslopearestillrecognizableintheinsular marginmorphology.TheCanaryIslandinsularmarginappearstobeacreationofMiocene-Pliocenemasswasting andmorerecentturbiditycurrentdepositionanderosion,andhemilepagicdeposition.FailuresoffshoreLaGomera areduetodebrisflowsand/orturbiditycurrents.Theseeventshaveobscuredearliermasswastingevents. Introduction discovered that volcanic edifices are quite extensive, much more that expected from the extent of volcan- In this study we use multi-beam data acquired in ism in the islands. Volcanic structures were imaged the Canary Islands by the Instituto Español de by multibeam recordings between Fuerteventura and Oceanografia to determine the role that landslides Gran Canaria and offshore Tenerife, La Gomera, El have played in the construction of the islands present Hierro and La Palma. Probable volcanic flows also morphology. In the course of our investigation we were imaged between Tenerife and La Gomera as 2 Figure1. SubmarinetopographyoftheCanaryIslandarchipelagoregion.BathymetriccontoursarefromGEBCOsheet5.08andbasemap fromU.S.NavalOceanographicOffice51017.InsertmapismodifiedfromWynnetal.(2000).Contourinmeters.1=Alegranza;2=Graciosa; 3=RoquedelOeste;4=RoquedelEste. well as salic necks on the eastern insular slope of La slopesoftheislandsofLaPalma,ElHierro,Tenerife, Gomera. The most spectacular of these features are FuerteventuraandGranCanaria(NavarroandCoello, the mega-avalanches, particularly those off Tenerife, 1989; Holcomb and Searle, 1991; Carracedo, 1994, ElHierroandLaPalma.Asotherstudieshavedemon- 1996; Masson and Watts, 1995; Watts and Masson, strated, landslides are amongst the most significant 1995; Masson, 1996; Masson et al., 1997; Guillou processes in the creation of the morphology of ma- etal., 1998; Urgelesetal., 1998, 1999; TeideGroup, tureoceanicvolcanicislands.Theyhavebeenreported 1997; Stillman, 1999). Masson et al. (2002) have fromtheHawaiianIslands(Mooreetal.,1989,1994), summarizedtheresultsoftheseinvestigations. Reunion Island (Labazuy, 1996) and the Canary Is- lands (Watts and Masson, 1995; Urgeles et al., 1997, 1999; Carracedo et al., 1999a, 1999b). Moore et al. Regionalsetting (1989, 1994) recognized at least 68 such flows off Hawaii, some of which are 200 km long, incorpo- The Canary archipelago is located on the continen- rate as much as 5000 km3 of volcanic material and tal rise off Cape Juby, northwest Africa (Figure 1). cover an area of 100,000 km2. Mass wasting facies FuerteventuraandLanzaroteattheeasternendofthe off Hawaii take two forms: (1) slow moving slumps, chainare100kmfromtheAfricancoast,andElHierro up to 110 km wide and up to 10 km thick, character- andLaPalmaatitswesternendare500kmfromthe ized by transverse blocky ridges and steep toes that coast.LanzaroteandFuerteventuraarealongthecrest are up to 230 km long, and (2) 0.05–2 km thick, fast of the northeast trending Canary Ridge, on the upper moving debris avalanches (Moore et al., 1989). To continental riseatawaterdepth ofabout 2000m. Its dateelevengiantslidesalsohavebeenmappedinthe northeast terminus is defined by the less than 200 m Canary Islands affecting the subaerial and submarine deep,flat-toppedConceptionBank.Thisridgemaybe 3 Figure2.TopographicmapoftheCanaryarchipelagoregion.Offshorecontoursinmetersarebasedonmulti-beamechosoundingdatacollectedduringthepresentinvestigationandonshore onesalsoinmetersfromdataprovidedbyServicioGeogra´ficodelEjercito,Cartograf´ıaDigital,100by100mgrid,Madrid. 5 Figure3. GeologicmapsofLanzaroteandFuerteventura. CompiledfromCoelloetal. (1992), CarracedoandRodr´ıguez-Badiola(1993), Ancocheaetal.(1996)andStillman(1999). aligned along the contact between attenuated con- of these volcanic structures, Dacia Seamount, is flat- tinental crust on the east and oceanic crust on the topped. Sediments in the lows between the ridges west (Emery and Uchupi, 1984). The rest of the grade south into the Canary Island Basin west of the archipelago, Gran Canaria, Tenerife, La Gomera, La CanaryRidgeandnorthintotheAgadirCanyonwith ◦ (cid:4) Palma and El Hierro, at water depths of 3000 to the drainage divide located near 30 30 N (Figure 1). 4000m, areonoceaniccrustofJurassicage(Uchupi TheseaflooroftheCanaryIslandsBasinrangesfrom et al., 1976). Gran Canaria, Tenerife and La Gomera 3000 m on its eastern side to 4000 m along its west- trend east-west parallel to the oceanic fracture zone ern side. Here a slight shallowing of the basin floor trends in the region with Tenerife’s long axis being to less than 4000 m reflects the subsurface high link- oblique to this trend. La Palma and El Hierro, at the ing La Palma and Ilhas Selvagens. A gap in the high ◦ (cid:4) ◦ (cid:4) westernendoftheislandchain,areoffsettothenorth near17 30 W,29 30 Nservesaspassagewayfortur- andsouthofthistrend(Figure1). bidity currents into the Madeira Abyssal Plain to the A subsurface oceanic basement high appears to west (insert, Figure 1). Gaps between the Canary Is- link La Palma to Ilhas Selvagens (Figure 1) (Uchupi lands along the southern side of the basin serve as et al., 1976). From the Ilhas to the northeast end of passagewaysforthesoutherlyflowingNorthAtlantic the Canary Ridge are two northeast trending ridges, DeepWater(NADW)atadepthof2000-3800mand subparallel to the Canary Ridge, along whose cres- northerly flowing Antarctic Bottom Water (AABW) tsareseamounts(DañobeitiaandCollette,1989).One below3800m.