Submarine Landslides Around Volcanic Islands
Anne Le FriantÉlodie LebasSally MorganSara LafuerzaM. J. HornbachMaya CoussensSebastian WattMichael CassidyPeter J. Talling
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Abstract:
IODP Expedition 340 successfully drilled, for the first time, large and likely tsunamigenic volcanic island arc landslide deposits. These cores provide evidence and tests of previous hypotheses for the composition, origin, and mode of transport of those deposits. Sites in the medial to distal parts of the landslide deposits offshore Montserrat and Martinique recovered seafloor sediment, comprising turbidites and hemipelagic deposits, and lacked the coarse and chaotic subaerial volcanic debris avalanche material. This supports the concepts that (i) the volcanic debris avalanche component of these landslides is restricted to proximal areas and tends to stop at the slope break and (ii) emplacement of volcanic debris avalanches in marine settings can trigger widespread and voluminous failures of preexisting low-gradient seafloor sediment. The most likely mechanism for generating these large-scale seafloor sediment failures appears to be the propagation of a décollement, from proximal areas that are loaded and incised by a volcanic debris avalanche. These results have implications for the magnitude of tsunami generation by volcanic island landslides. Volcanic island landslides composed of mainly seafloor sediment may form smaller magnitude tsunamis than equivalent volumes of subaerial block-rich mass flows rapidly entering water.Keywords:
Subaerial
Submarine landslide
Seafloor Spreading
Submarine volcano
Volcanic cone
Subaerial
Submarine landslide
Tsunami wave
Submarine volcano
Mass movement
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Stromboli volcano (Aeolian Arc, Italy) experiences many mass failures along the Sciara del Fuoco (SdF) scar, which frequently trigger tsunamis of various sizes. In this work, we simulate tsunami waves generated by landslides occurring in the SdF through numerical simulations carried out in two steps: (i) the tsunami triggering, wave propagation and the effects on Stromboli are simulated using the 3D non-hydrostatic model NHWAVE; (ii) generated train waves are then input into the 2D Boussinesq model FUNWAVE-TVD to simulate wave propagation in the Southern Tyrrhenian Sea (STS). We simulated the following scenarios: (i) the tsunami runup, inland inundation and wave propagation at Stromboli triggered by submarine landslides with volumes of 6, 10, 15 and 20 × 106 m3 and subaerial landslides with volumes of 4, 6, 10 and 30 × 106 m3; (ii) tsunami propagation in the STS triggered by submarine landslides with volumes of 10 and 15 × 106 m3 and by subaerial landslides with volumes of 6 and 30 × 106 m3. We estimate that the damages of the last relevant tsunami at Stromboli, which occurred in 2002, could have been generated either by a subaqueous failure of about 15-20 × 106 m3 along the SdF or/and a subaerial failure of about 4-6 × 106 m3. The coasts most affected by this phenomenon are not necessarily located near the failure, because the bathymetry and topography can dramatically increase the waves heights locally. Tsunami waves are able to reach the first Stromboli populated beaches in just over 1 minute and the harbour in less than 7 minutes. After about 30 minutes the whole Aeolian Arc would be impacted by maximum tsunami waves. After 1 hour and 20 minutes, waves would encompass the whole STS arriving at Capri.
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Submarine landslide
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Rockslide
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Abstract The Meiwa tsunami of AD 1771 is regarded as an extremely strong tsunami event causing devastating damage in Japan in historical times. Earlier studies explored the possibility that a submarine landslide enhanced the Meiwa tsunami waves. We collected detailed seafloor bathymetry data, sub-bottom structure data and surface sediments in a putative Meiwa tsunami source region to ascertain any signature related to a submarine landslide in the forearc region, which is located south of Ishigaki-jima. The forearc-region seafloor is characterized by its surface submarine landslide morphology. However, the investigated magnetic fabric of surface sediment revealed that there was no landslide mass deposit during historical times. The described landslide morphology in the basin is unrelated to the generation or enhancement of the AD 1771 Meiwa tsunami, although the disturbed relief in the topography of the study area indicates that the forearc region is susceptible to slope failure because of its tectonic setting.
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Submarine landslide
Seafloor Spreading
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Seafloor Spreading
Submarine landslide
Flank
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A series of large blocks from the 44-North Slide, offshore Oregon, impacted the seafloor with sufficient force to induce a broad zone of deformation. In 2017, we acquired a seismic profile from the headwall area to the outer toe of this slide. Previous work identified this slide, but it has not been imaged at high resolution before this survey. A striking surficial feature is a collection of blocks that lie downslope from an amphitheater-shaped headwall. The blocks traveled up to 20-km horizontally and about 1200-m vertically down a 13° slope and now cover an area of ~100 km2. The blocks have rough and angular edges that extend up to 400-m above the surrounding seafloor. Seaward of the blocks, a 10-km zone of sediment is deformed, horizontally shortened by 8%. We interpret the strain field to be a result of the dynamic impact forces of the slide. This suggests a high-mobility failure with tsunamigenic potential. It is unclear what preconditioned and triggered this event, however, earthquake-induced failure is one possibility. Gas hydrate dissociation may have also played a role due to the presence of a bottom-simulating reflector beneath the source area. This study underscores the need to understand the dynamic processes of submarine landslides to more accurately estimate their societal impacts.
Seafloor Spreading
Submarine landslide
Geohazard
Seabed
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Subaerial
Submarine volcano
Volcanic cone
Shield volcano
Volcanic plateau
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Subaerial
Submarine landslide
Mass wasting
Volcanic cone
Caldera
Submarine volcano
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Much remains to understand the dynamic processes during the flow of submarine landslides. A first relevant problem is to explain the extraordinary mobility of submarine landslides, which has no comparison in subaerial mass movement. Another challenging question is the apparent disparity between submarine landslides that remain compact for hundreds of kilometres and those that disintegrate during the flow, finally evolving into turbidity currents. This problem is linked to a central ongoing debate on the relative importance of turbidity currents versus submarine landslides in reshaping the continental margin. Based on three epitomic case studies and on laboratory experiments with artificial debris flows of various composition, we suggest a possible explanation for the disparity between compact and disintegrating landslides, identifying the clay-to-sand ratio as the key control parameter.
Subaerial
Submarine landslide
Turbidity current
Debris flow
Continental Margin
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The study conducted during this work, is focused in the interpretation of morphological features on the seafloor in the Stromboli Island (Tyrrhenian Sea).Stromboli is the northwest island of the Aeolian archipelago and comprises an area of 12.6 km 2 . It emerges 924 meters above the sea level and extends up to 3000 meters (m) under sea level. Submarine portions of Stromboli volcano account for about 98% of the whole extent of the volcanic edifice. The bathymetric map was made from processing data acquired during the experiment Tomo-Etna 2014. The preliminary seafloor interpretation; give us a notable morphological division by sectors, which are dominated by different morphological features patterns. The northeast and southwest flanks are mainly characterized by narrow platform in the first 120 m depth. The northwest and southwest upper slope are dominated by morphologies related with slope instability processes, related with submarine landslides events. Particularly the NW flank is affected by the continuation of the note Sciara del Fuoco (SdF). On the seafloor in the SW flank, were detected the presence of small craters, which present a NE-SW trend almost parallel to the main trend of the volcano. We supposed that these morphologies are hydrothermal vent or smokers. In the upper slope of NE sector is remarkable the presence of a well-developed network of gullies, give place a really younger turbidity system.
Seafloor Spreading
Submarine volcano
Volcanic cone
Bathymetric chart
Archipelago
Submarine landslide
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