title: Hazard potential of volcanic flank collapses raised by new megatsunami evidence.
abstract: Large-scale gravitational flank collapses of steep volcanic islands are hypothetically capable of triggering megatsunamis with highly catastrophic effects. Yet, evidence for the generation and impact of collapse-triggered megatsunamis and their high run-ups remains scarce or is highly controversial. Therefore, doubts remain on whether island flank failures truly generate enough volume flux to trigger giant tsunamis, leading to diverging opinions concerning the real hazard potential of such collapses. We show that one of the most prominent oceanic volcanoes on Earth-Fogo, in the Cape Verde Islands-catastrophically collapsed and triggered a megatsunami with devastating effects ~73,000 years ago. Our deductions are based on the recent discovery and cosmogenic (3)He dating of tsunamigenic deposits found on nearby Santiago Island, which attest to the impact of this giant tsunami and document wave run-up heights exceeding 270 m. The evidence reported here implies that Fogo's flank failure involved at least one fast and voluminous event that led to a giant tsunami, in contrast to what has been suggested before. Our observations therefore further demonstrate that flank collapses may indeed catastrophically happen and are capable of triggering tsunamis of enormous height and energy, adding to their hazard potential.
authors.affiliation: School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol BS8 1RJ, UK. ; Lamont-Doherty Earth Observatory at Columbia University, Comer Geochemistry Building, 61 Route 9W, P. O. Box 1000, Palisades, NY 10964-8000, USA.
authors.forename: Ricardo S
authors.initials: RS
authors.lastname: Ramalho
authors.affiliation: Lamont-Doherty Earth Observatory at Columbia University, Comer Geochemistry Building, 61 Route 9W, P. O. Box 1000, Palisades, NY 10964-8000, USA.
authors.forename: Gisela
authors.initials: G
authors.lastname: Winckler
authors.affiliation: Departamento de Geologia, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal. ; Instituto Dom Luiz, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal.
authors.forename: José
authors.initials: J
authors.lastname: Madeira
authors.affiliation: School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol BS8 1RJ, UK. ; Earth-Life Science Institute, Tokyo Institute of Technology, 2-12-1-IE-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan.
authors.forename: George R
authors.initials: GR
authors.lastname: Helffrich
authors.affiliation: Centro de Vulcanologia e Avaliação de Riscos Geológicos, Universidade dos Açores, Rua da Mãe de Deus, Edifício do Complexo Científico, 3° Andar-Ala Sul, 9500-321 Ponta Delgada, Açores, Portugal.
authors.forename: Ana
authors.initials: A
authors.lastname: Hipólito
authors.affiliation: Instituto Dom Luiz, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal. ; Divisão de Geologia e Georecursos Marinhos, Instituto Português do Mar e da Atmosfera I.P., Rua C do Aeroporto, 1749-077 Lisboa, Portugal.
authors.forename: Rui
authors.initials: R
authors.lastname: Quartau
authors.affiliation: School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol BS8 1RJ, UK.
authors.forename: Katherine
authors.initials: K
authors.lastname: Adena
authors.affiliation: Lamont-Doherty Earth Observatory at Columbia University, Comer Geochemistry Building, 61 Route 9W, P. O. Box 1000, Palisades, NY 10964-8000, USA.
authors.forename: Joerg M
authors.initials: JM
authors.lastname: Schaefer
keywords: Cape Verde Islands; Fogo; Islands; Santiago; geology; megatsunami; natural hazard; tsunami; volcanic flank collapses; volcanoes