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The architecture of explosive deep-water volcanoes in the Azores Plateau

Christian Hübscher1 , Annalena Friedrich1, Jonas Preine1, Christoph Beier2, Anthony Hildenbrandt3, Paraskevi Nomikou4, Pedro Terrinha5, Benedikt Weiß1,6

  • Affiliations: 1Institut für Geophysik, Universität Hamburg, Hamburg, Germany; 2Department of Geosciences and Geography, University of Helsinki, Finland; 3GEOPS, Univ. Paris-Sud, CNRS, Université Paris-Saclay, Orsay, France; 4Laboratory of Physical Geography, National & Kapodistrian University of Athens, Athens, Greece; 5 Portuguese Institute for the Ocean and Atmosphere (IPMA), Lisbon, Portugal; 6Present address: Bundesamt für Seeschifffahrt und Hydrographie (BSH), Hamburg, Germany

  • Presentation type: Poster

  • Presentation time: Tuesday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 77

  • Programme No: 6.2.13

  • Theme 6 > Session 2

Abstract

In deep-sea settings, lava fragmentation is generally thought to result from quenching rather than explosive eruptions due to magmatic volatile pressure. However, several studies provide evidence of explosive submarine eruptions at significant water depths. Geophysical evidence remains sparse though. In this study, we use high-resolution seismic reflection data to reconstruct the polygenetic development of deep-water volcanoes on the Azores Plateau. The studied volcanoes have formed along the southern diffuse plate boundary of the Azores Plateau, which is characterized by dextral transtensional movement. Around 10 million years ago, explosive eruptions led to the formation of a few kilometer-wide diatremes within pelagic sediments. Subsequently, intraplate lavas flooded presumably more than 10.000 km2 of the plateau, and shield volcano like edifices filled craters on the surface of the diatremes in paleo water depths beneath 2.2 km. After a non-volcanic phase of approximately 5 million years, a second volcanic phase began with explosive eruptions above the diatremes, displacing the intervening pelagic sediments over several kilometers. By the end of this volcanic phase, a volcanic edifice about 400 meters high with a crater approximately 500 meters wide had formed. The crater was filled with effusively erupted lava by the end of the volcanic activity.  The present-day volcanic edifices are 4--4.5 km wide and 500--550 meters high. This study underscores the significance of reflection seismic data for studying underwater volcanoes, as it provides the critical insights needed to infer explosive underwater eruptions, which bathymetric data alone cannot offer.