Composition, geometry, and emplacement dynamics of a large volcanic island landslide offshore Martinique: From volcano flank‐collapse to seafloor sediment failure?

Abstract

+33 (0) 1 83 95 76 38Key points: -First drilling into submarine landslide deposits offshore volcanic island -Large (300 km 3 ) submarine landslide deposit offshore Martinique comprises mainly deformed seafloor sediment, in a single frontally emergent morphology Research ArticleGeochemistry, Geophysics, Geosystems DOI 10.1002/2015GC006034This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process which may lead to differences between this version and the Version of This article is protected by copyright. All rights reserved. 2 AbstractLandslides are common features in the vicinity of volcanic islands. In this contribution, we investigate landslides emplacement and dynamics around the volcanic island of Martinique based on the first scientific drilling of such deposits. The evolution of the active Montagne Pelée volcano on this island has been marked by three major flank-collapses that removed much of the western flank of the volcano. Subaerial collapse volumes vary from 2 to 25 km 3 and debris avalanches flowed into the Grenada Basin. High-resolution seismic data (AGUADOMAR -1999, CARAVAL -2002 and GWADASEIS -2009) is combined with new drill cores that penetrate up to 430 m through the three submarine landslide deposits previously associated to the aerial flank-collapses (Site U1399, Site U1400, Site U1401, IODP Expedition 340, Joides Resolution, March-April 2012). This combined geophysical and core data provide an improved understanding of landslide processes offshore a volcanicisland. The integrated analysis shows a large submarine landslide deposit, without debris avalanche deposits coming from the volcano, comprising up to 300 km 3 of remobilized seafloor sediment that extends for 70 km away from the coast and covers an area of 2100 km 2 .Our new data suggest that the aerial debris avalanche deposit enter the sea but stop at the base of submarine flank. We propose a new model dealing with seafloor sediment failures and landslide propagation mechanisms, triggered by volcanic flank-collapse events affecting Montagne Pelée volcano. Newly recognized landslide deposits occur deeper in the stratigraphy, suggesting the recurrence of large-scale mass-wasting processes offshore the island and thus, the necessity to better assess the associated tsunami hazards in the region.This article is protected by copyright. All rights reserved. IntroductionFlank-instabilities are a recurrent process in the long-term evolution of many volcanoes [Siebert, 1984;McGuire, 1996]. Exceptionally large volcanic landslides have been recognized offshore oceanic intraplate islands such as Hawaii [Moore et al., 1989, Moore et al., 1994, the Canary Islands [Carracedo, 1999; Masson et al., 2002], La Réunion Island [Labazuy, 1996; Oehler et al., 2004Oehler et al., , 2008 and in subduction zones such as the LesserAntilles [Deplus et al., 2001; Le Friant et al., 2003a,b;Boudon et al., 2007]. The scale of some of these events exceeds the la...

Revisiting the tsunamigenic volcanic flank collapse of Fogo Island in the Cape Verdes, offshore West Africa

“…A similar two-fold nature of volcanic flank-collapse depositshummocky debris avalanche deposits accompanied by acoustically transparent to seismically chaotic deposits with a comparatively smooth upper surfacehas also been reported for flank-collapses at other locations, including in the Lesser Antilles (Watt et al, 2012a, b;Le Friant et al 2015;Brunet et al 2016); at La Réunion (Indian Ocean; Lebas et al 2018); and at Ritter Island (Papua New Guinea; Karstens et al 2019;Watt et al 2019). Drilled cores retrieved during IODP Expedition 340 in the Lesser Antilles indicated that widespread, seismically chaotic deposits (interpreted as equivalent to our MTD-B) primarily consist of hemipelagic mud interbedded with a combination of tephra, volcaniclastic layers, or bioclastic turbiditic deposits, which have undergone varying degrees of deformation (Le Friant et al 2015;Brunet et al 2016). To explain these findings, Le Friant et al (2015) proposed a failure model where the loading of seafloor sediment by volcanic debris avalanche deposits triggered sediment destabilization…”

“…Many such events have volumes in the order of tens to hundreds of cubic kilometres, e.g. at Nisyros Volcano in the Aegean Sea (Tibaldi et al 2008;Livanos et al 2013); in the Lesser Antilles Arc (Lebas et al 2011;Le Friant et al 2015;Brunet et al 2016); in the Canary Islands (Krastel et al 2001;Masson et al 2002;León et al 2017); and in the Cape Verde Islands (Masson et al 2008). However, even comparatively small-volume volcanic flank-collapses, such as the 0.22-0.3 km 3 Anak Krakatau flank-collapse in December 2018 (Grilli et al 2019), may result in catastrophic tsunamis.…”

Understanding the Evolution of an Oceanic Intraplate Volcano From Seismic Reflection Data: A New Model for La Réunion, Indian Ocean

“…The Integrated Ocean Drilling Program Expedition 340 carried out offshore the Lesser Antilles provided for the first time evidence for the composition and origin of such chaotic units offshore Montserrat and Martinique Islands. The seismically chaotic deposits were successfully drilled and exclusively recovered seafloor sediment (including mud, tephra layers, and turbidites), revealing a complete lack of volcanic debris avalanche deposits (Brunet et al, ; Le Friant et al, ). Le Friant et al () interpreted these “seismically chaotic facies” deposits as resulting from widespread deformation of pre‐existing sediment on the abyssal plain, triggered by the emplacement of debris avalanche deposits on the edifice flank.…”

Integrated geotechnical, sedimentological and geophysical investigation of seafloor instabilities in the Gulf of Lions Western Mediterranean

“…volcanic flanks (Lafuerza et al 2014;Hornbach et al 2015;Brunet et al 2016); passive margins (Sawyer et al 2009); glacial margins (Laberg & Camerlenghi 2008). With the example provided from the GoL, we further support the evidence that lithological heterogeneity within the sediment successions is a key to localisation of seafloor instability.…”