1

InterRidgeWorkshoponSeamountsandIslandsAssociatedWithMid-OceanRidges(19-21September2019)

Workshopparticipants1

Seamounts are large underwatermountains, here consideredmore than 1 kmhigh,whichcanbeformedbyeithervolcanicortectonicprocesses. Seamountsand islands associated with mid-ocean ridges are sites of great interest forresearchers from a variety of scientific disciplines. Researchers commonlyrequire data and knowledge from other disciplines to make progress, hencework can be highlymultidisciplinary in this field. A workshopwas thereforeconvenedtoaddressthesespecialenvironmentsandtheinterdisciplinarynatureoftheresearch,withaparticularfocusonfuturework.TheworkshopwasheldoverthreedaysattheConventodasTrinas,aformerconventnowoccupiedbytheInstitutoHidrográfico,thePortugueseHydrographicOfficeinLisbon.Forthefirstdayandahalf,researcherspresentedtalksandposters. Subsequently,theattendees worked on subject-specific priorities within breakout groups and1Seeendofreportforparticipantslist

2

finally discussed collectively ways for the community to move the subjectsforwardthroughcollaboration,newfieldwork,anddataandknowledgesharing.FollowingawelcomeaddressbythedirectoroftheInstitutoHidrográfico,talksinthemorningsofthefirstandseconddayaddressedgeologicaloriginsofthesestructures, their oceanography and biology, as well as funded and plannedresearchprogrammes:UpdateonInterRidgeactivities-KamilSzafrańskiIntroductiontothisworkinggroup,workshoptasks,andsomegeologicalknown

unknownsofseamountsandislands-NeilMitchellSeamounts and oceanic igneous features in the Northeast Atlantic: A Link

betweenplatemotionsandmantledynamics-CarmenGainaMid-oceanridgeislandsandseamounts:currentchallengesandfuturedirections

-RicardoRamalhoThestudyofinsularshelvesasakeyforunderstandingthegeologicalevolution

ofvolcanicislands:examplesfromtheAzoresarchipelago-RuiQuartauDeep-seasoft-bottombenthiccommunities:Exploringbiogeographyandgenetic

connectivityofsoutheastPacificSeamounts-EduardoQuirogaThe biogeographic Azorean paradox and the contribution of physical

oceanography-SérgioÁvilaThe evolution of oceanic intraplate volcanoes close to mid-ocean ridges: the

Azoresislands-ChristophBeierSeamounts at the 69¯N SPAR offset, Kolbeinsey Ridge, N-Atlantic - Bryndís

BrandsdóttirTheGlobalSeamountsProject:buildingonpastseamountresearchtogoforward

onaglobalscale-MalcolmClarkGlobalOceansequipmentcapabilities-JimCostopulosTheNOAAASPIREprogram-KaseyCantwellTheiAtlanticproject-TelmoMoratoPosterspresentationsfurtherexpandedthebackground:Tectonic implication on seafloor geomorphology, upper slope, Western Niger

delta-AshiruO.R.&WuSGeomorphological evolution of the Chilean volcanic oceanic islands and

seamounts-LauraBecerril&LuisE.LaraThe evolution of oceanic intraplate volcanoes close to mid-ocean ridges: the

Azoresislands-ChristophBeier,RenéH.W.RomerandKarstenM.HaaseThreatsfromsubmarinelandslidesaroundmid-oceanridgevolcanicislands:the

centralAzores-Yu-ChunChang,NeilMitchell&RuiQuartauSurface deformation of the Azores Islandsmeasured by Copernicus Sentinel-1

SARinterferometry-EricJ.FieldingSlopeInstabilityonOceanicCoreComplexes-AggelikiGeorgiopoulou,Bramley

Murton, Maria Judge, Paraskevi Nomikou, Steve Hollis, Oisin McManus,SebastianKrastel,IsobelYeo&theTOSCAteam

ReflectionseismicandbathymetricstudyofunderwatervolcanoesoftheAzoresPlateau-ChristianHübscher,ParaskeviNomikou,JosefineStakeman,PedroTerrinha&ChristophBeier

3

St.PaulTransformSystemearthquakes:anexampleofseismicityoriginatedbytranspressivetransformfaultandfracturezonereactivation-GuilhermedeMelo,MarciaMaia,AdersondoNascimento,JuliePerrot,AlexeySukhovich&ThomasCampos

Last Interglacial fossiliferous sequences from Santiago Island (Cabo VerdeArchipelago):palaeoecologyofNossaSenhoradaLuzBay,arareexampleofaprotectedbay involcanicoceanic islands -CarlosS.Melo,AnaC.Rebelo,Ricardo S. Ramalho, José Madeira, Esther M. González, Alfred Uchman,PatríciaMadeira,CarlosM.daSilva&SérgioÁvila

GondwanariftingassociatedwiththeformationofanewLargeIgneousProvincein the southwestern IndianOcean? - ChristineMeyzen,MarciaMaia, JasonMorgan, Tod Waight, Christophe Hemond, Andrea Marzoli, AnastassiaBorisova,HiroshiSato&MatteoMassironi

Contouritedrifts off oceanic islands?Ahigh-resolution archive for climate andoceanographic changes and tectono-magmatic activity - C. Roque, F.J.Hernández-Molina,P.Madureira&R.Quartau

Post-riftridge-"plume"interaction:ThecaseofMadeira-ToreRise-A.RitaRosa,LuísaPintoRibeiro,PedroMadureira&JoãoMata

Gravitational, erosional, sedimentary and volcanic processes on the submarineenvironmentof Selvagens Islands (MadeiraArchipelago,Portugal) -RúbenSantos,RuiQuartau,AntónioBrumda Silveira,RicardoRamalho&AuroraRodrigues

SubmarineslopefailurecausedbyseamountsubductionattheJavaTrench-newinsightsfromFiveDeepsExpedition-HeatherStewart,JoanaGafeira,AlanJ.Jamieson&CassieBongiovanni

The Saint Peter and Saint Paul Archipelago (Equatorial Atlantic Ocean): Thetectonic joint system as evidence of compressive present-day activetectonism - Thomas F da C Campos, Guilherme de Melo, Susanna Sichel,Marcia Maia, Daniele Brunellis, Kenji Motoki, Akihisa Motoki, EstefanFonseca&ThaisVargas

SubmarinePlatformDevelopmentbyErosionofaSurtseyanConeatCapelinhos,FaialIsland,Azores-ZhongweiZhao,NeilC.Mitchell,RuiQuartau,FernandoTempera&LucyBricheno

Coastalerosionratesoflavadeltasaroundoceanicislands-ZhongweiZhao,NeilC.Mitchell,RuiQuartau&RicardoS.Ramalho

Thesubjectbreakoutgroupsaddressedfourbroadsubjectareas.Withinthefirstgroup, the majority of the geochemical and geodynamic hypotheses thatmembersconsideredimportanttotestconcernedprocesseslinkingdeep,mantleand crustal processes with those at the surfaces of seamounts and islands.Research questions encompassed the structure of the lithosphere andasthenosphere of the regions around seamounts and islands and the lateralextentsof the zonesofmantlemeltingunderneath them.The tectonic regimesthatmayinfluencetheformationandevolutionofseamountsclosetomid-oceanridgesvarysignificantlyfromalocaltoregionalscale.Thisvariationisofgreatimportanceininterpretingexistingandnewgeodynamicandgeochemicaldata.Further deep, mantle-imaging geophysical studies are needed to reveal thestructures within and underlying seamounts on scales of 100s to 1000s of

4

kilometres from seismic tomography, reflection and refraction capable ofresolvingvelocityanisotropy.Theworkinggroupagreedthatbridgingbetweenmethods and spatial scales of geophysics and geochemistry should be amajoraim.Propertiesthatshouldbetargetedincludethermalstateandheatflow,thetimingandratesofmeltascent,aswellascrustalmorphologyandcomposition.Onemajorfocuswillbeimprovingtheunderstandingoftheascentthroughandstagnationofmagmaswithinthecrust, inparticularhowthosemovementsareaffected by local and regional stress fields. The implications arisingwill be ofgreat importance forprocessesat thesurface includingeruptiondynamics, theformationofhydrothermalsystemsandmicrobialcommunities.The second group considered the higher-level structural architectures ofseamountsandislands.Internalstructuresarepotentiallyrevealedat"tectonicwindows", deep fault escarpments exposing their internal features. Geologicalhazardstopopulationsandinfrastructureareexpectedtoariseintheseislandsbecauseofcostalerosion,landslides,volcaniceruptionsandtsunamis.Itisstillunclearhowmuchthesephenomenaaffectareasinthefarfield.Italsoremainsunclearwhatconditionsleadtolandslidemovementsortriggersofmovements,or how frequently they occur. It is unclear how loading of the underlyinglithospherebyvolcanoesaffectslithosphericstressandthegeometriesofactivefaults. We currently do not know if this implies significant uncertainty inpredictingthreatsofearthquakestolocalpopulations.Thegrouprecommendedthat future research efforts should focus on combining land and offshoredatasets toaddress theseproblems. Inparticular,effortsareneeded tocollectdatainnearshoreareasthatareoftenneglectedinmarinesurveysforsafetyandefficiency reasons. Geophysical and geological data from diverse researchgroupsshouldbecombinedtoprovidebettersyntheses.Moreeffortisnecessarytomake these data freely available to the scientific community after embargoperiods. Greateruseofinstrumentsisneededthatcanrecordactivegeologicalprocesses,suchasGPSandInSARonlandandoceanbottomseismometersandpressuresensorsunderwater.Thethirdgroupconsideredthesedimentsoverlyingandsurroundingseamountsand islands, their influences and the varied information that they provide.Deposition and erosion of sediments are affected by ocean currents and byoscillating currents from surface waves. Physical oceanographic modelling ofcurrents has improved greatly, potentially helping us to explain patterns ofsedimentdeposition, though isstilldependenton theresolutionofbathymetrydata, which are highly varied in mid-ocean ridge settings. Data from oceancurrent meters and other sensors are needed to validate those models.Numerical ocean models could be useful to test information obtained fromsediments on past paleoceanographic and paleoclimatic conditions. Forexample,speciescapableofdispersiononlybyraftingcansuggestthepresenceof surface currents that are very different from modern currents. Sedimentcorescouldbevaluableforrevealinghowcurrentsattheseabedhavechangedover time (effects on grain sizes and hiatuses) and how conditions in theoverlyingsurfaceoceanhavechanged,exploitingnewdevelopments inorganiccarbon and other environmental proxies. The stratigraphy within sedimentsaroundtectonicseamounts(oceaniccorecomplexesandtransform"push-ups")

5

could help in working out their developments. Mid-ocean ridge islands areuseful for paleoclimatework simply by virtue of their central positionswithintheoceanbasins,solakeandothersedimentrecordscanfillspatialgapsintheglobalpaleoclimaterecord.Thefourthgroupconsideredbiologicalaspects. Asthesecanbebroadranging,discussionwasfocusedonacentralthemethatwouldalignwiththegeologicaland oceanographic interests, addressing biological and ecosystem functioningcharacteristicsanddifferencesbetweenmid-oceanridgepeaks,mid-oceanridgeisland slopes, and seamounts. More complete information is needed on theoccurrences of deep-sea species and on the biodiversity distribution patternswithin and between these habitats, but also in understanding howenvironmental properties cause variations in these patterns. Environmentaldataareneededathigherspatialandtemporalresolutionforthistobeeffective,which can potentially now be collected using gliders, moorings and floats.Another important knowledge gap discussed relates to the spatial scale ofconnectivitypatternsalongandacrosstheridges,seamountsandislandslopes.The group considered an important question: what are the distances of suchconnectivityandwhatdeterminesthosedistances?Geneticapproachestotheseproblems will be important, but need to be complemented with studies ofreproductivebiologyandlarvaldispersalandsettlement.Hence,futureresearchneedstoaddresswhethermid-oceanridgeseamountsplayanimportantroleinlarval retention (e.g., of hydrothermal vent fauna), facilitating recruitment onotheradjacenthabitats. Itneedstoaddresstemperatureanddepthbarrierstoconnectivity (e.g., for sponges), and the role of ocean currents in connectivity.Thebroadquestionhasimplicationsfortheresilienceofcommunitiestoclimatechange. The group identified three further important research questions thataddress the distribution and connectivity of populations associated withmid-ocean ridge habitats: Does the trophic architecture (measured by isotopicstudies) differ between seamounts, ridge peaks and seamounts? What is thesphere of influence of the different habitats and faunal communities? Howwidespread is the inputofchemosyntheticproduction fromhydrothermalventsystems that occur along mid-ocean ridges, what is its variability and whatdrivesit? Thesequestionsaddressbothfundamentalecologicalissues,aswellasbeingrequirementsforrobustmanagementofhumanactivitiesintheseareas.They require a structured survey design that addresses both spatial andtemporal variability, and multi-disciplinary studies. A key input from othersectionsof the InterRidgeWorkingGroup is informationonthesubstrate type,andgeochemicalcomposition.Duringthefinalday,theparticipantsdiscussedtherangeofissuesidentifiedbythebreakoutgroups,andrefinedtheaimsoftheoverallworkinggrouptowardsimproved understanding of the pathways of material and energy flow onseamountsandislandsassociatedwithmid-oceanridgesandtheirrolesinactingasconduitsorbarriers. Thedefinitionoftheworkinggroupwasalsoreshapedasactingasanumbrellaforfundamentalandappliedresearchonlargeedificesthat formed in proximity tomid-ocean ridges, excluding those that formed inintraplateenvironments.Therolesofseamountsduringcyclingofmaterialandenergyintheframeworkofplatetectonicsarestilllargelyunknownduetoalack

6

of data and samples. However, the pathways ofmaterial and energy throughseamounts and the surrounding crust are essential for the hydrosphere andbiosphere. Information on them would link the research of the InterRidgeworkinggroup to theGlobalSeamountsProject, amajor initiative thataims tocharacterize and model the ecologies of distant seamount habitats. Allparticipants agreed that progress in the subjectwould benefit from continuednetworking. They suggested focus sites for the NOAA Aspire initiative andrecommendedestablishingastablenetwork,tooperateglobally.Theworkshopfinished by evaluating the possibilities for developing a larger networkingproposal.Thiswillbethesubjectofasecondworkshoptobeheldin2020.Acknowledgements:TheparticipantsthanksupportforthisworkshopfromtheInterRidgeandScientificCommitteeonOceanResearch.Inparticular,wethankthe Portuguese Instituto Hidrográfico for kindly allowing us to occupy someroomsoftheConventodasTrinasforthethreedaysofthisworkshop.TheworkshopwasconvenedbyNeilMitchell,RuiQuartauandChristophBeier.The participants were: Ana Rita Rosa (Universidade de Lisboa, Portugal),Aggeliki Georgiopoulou (University of Brighton, UK), Bryndis Brandistottir(University of Iceland), Carlos Melo (Universidade de Lisboa), Carmen Gaina(UniversityofOslo,Norway),ChristineMeyzen(UniversitàdegliStudidiPadova,Italy), Christoph Beier (University of Helsinki, Finland), Cristina Roque (TaskGroup for the Extension of Portuguese Continental Shelf (EMEPC), Portugal),Eduardo Quiroga (Pontificia Universidad Católica de Valparaíso, Chile), EricFielding (Jet Propulsion Laboratory, California Institute of Technology, USA),Fernando Ornelas Marques (Universidade de Lisboa), Guilherme de Melo(FederalUniversity of RioGrande doNorte, Brazil), Inês Tojeira (EMEPC), JimCostopulos (Global Oceans, New York, USA), Joana Gafeira (British GeologicalSurvey, UK), Joana Xavier (Universidade do Porto, Portugal), Kamil Szafrański(InterRidge, Institut de Physique du Globe de Paris, France), Kasey Cantwell(NOAAOfficeofOceanExplorationandResearch,USA),LauraBecerrilCarretero(Geological Survey of Chile, Chile), Luísa Ribeiro (EMEPC), Malcolm Clark(National InstituteofWater&AtmosphericResearch,NewZealand),NadineLeBris (Université Pierre et Marie Curie, France), Neil Mitchell (University ofManchester, UK), Olusola Ashiru (Chinese academy of Science, Sanya, China),Paraskevi Nomikou (University of Athens, Greece), PedroMadureira (EMEPC),Ricardo Ramalho (Universidade de Lisboa), Rúben Santos (InstitutoHidrográfico, Portugal), Rui Quartau (Instituto Hidrográfico), Sérgio Ávila(UniversidadedosAçores,Portugal),SimoneInnocentini(SapienzaUniversitàdiRoma, Italy),TelmoMorato(UniversidadedosAçores),TeresaRafael(EMEPC),Yu-Chun Chang (University of Manchester) and Zhongwei Zhao (University ofManchester). Remote participant: Dmitry Aleynik (Scottish Association forMarineScience,Oban,UK).