The products of eruptive and mass-wasting processes that built island arc volcanoes are better preserved in marine deposits than on land. Holes U1397A and U1399A drilled during IODP Expedition 340 ...provide a 1.5 Ma record of the volcanic history of Martinique.
14
C dating and δ
18
O patterns are used to reconstitute the chronostratigraphy of tephra, volcaniclastic turbidites, and mass-wasting events (traced by debris avalanches, debrites, and duplication and deformation of pre-existing sediments), leading to a new volcanic history of Montagne Pelée and Pitons du Carbet volcanoes. The top 50 m of core U1397A provides a continuous high-resolution sedimentation record over the last ∼130 ka. The sedimentation record deeper than 50 m in core U1397A and in the whole core U1399A is discontinuous because of the numerous sliding and deformation events triggered by debris avalanches related to flank collapses. Three successive activity periods are identified since ∼190 ka: the “Old Pelée” until 50 ka, the “Grand Rivière” (50–20 ka), and the “Recent Pelée” (20 ka—present day). The first two periods have the highest volcanic deposition rates offshore but very little outcrop on land. The whole magmatic activity of Mt Pelée comprises silicic andesites, but mafic andesites were also emitted during the whole “Grand Rivière.” At ∼115 ka, a major flank collapse (“Le Prêcheur”) produced a debris avalanche and submarine landslide that affected sea floor sediments by erosion and deformation up to ∼70 km from the shore. The Pitons du Carbet volcano was active from 1.2 Ma to 260 ka with numerous large flank collapses at a mean rate of 1 event every 100 ka. The average deposition rate of tephra fall offshore is much less than that at Mt Pelée. Our data show that correlations between the timing of large landslides or emission of mafic magmas and rapid sea level rise or lowstands suggested by previous studies are not systematic. The reconstituted chronostratigraphy of cores U1397A and U1399A provides the framework necessary for further studies of the magma petrology and production rates and timing of the mechanisms triggering flank collapses and related submarine landslides of Mt Pelée and Pitons du Carbet
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Abstract
The seismic hazard posed by submarine faults and the capacity of submarine earthquakes to trigger mass wasting are poorly understood because we lack detailed characterizations of coseismic ...ruptures at the seafloor. Here, we present comprehensive mapping of a seafloor rupture caused by the 2004
M
w
6.3 Les Saintes earthquake on the Roseau normal fault in the Lesser Antilles. We report the visual characteristics, displacement profile, and note pronounced asymmetry of the rupture that bears similarities with well-studied subaerial normal fault ruptures. We also identify footwall-derived mass wasted debris that locally cover the coseismic rupture, and show that ground accelerations of 0.1–0.2 g can trigger submarine mass wasting events in well consolidated bedrock along unstable, over-steepened, scarps. Our study demonstrates the potential of underwater vehicles for detailed mapping of seafloor ruptures and hints at a key role for earthquakes in shaping submarine bedrock landscapes by triggering mass wasting events.
Using temperature gradients measured in 10 holes at 6 sites, we generate the first high fidelity heat flow measurements from Integrated Ocean Drilling Program drill holes across the northern and ...central Lesser Antilles arc and back arc Grenada basin. The implied heat flow, after correcting for bathymetry and sedimentation effects, ranges from about 0.1 W/m2 on the crest of the arc, midway between the volcanic islands of Montserrat and Guadeloupe, to <0.07 W/m2 at distances >15 km from the crest in the back arc direction. Combined with previous measurements, we find that the magnitude and spatial pattern of heat flow are similar to those at continental arcs. The heat flow in the Grenada basin to the west of the active arc is 0.06 W/m2, a factor of 2 lower than that found in the previous and most recent study. There is no thermal evidence for significant shallow fluid advection at any of these sites. Present‐day volcanism is confined to the region with the highest heat flow.
Key Points
Heat flow in the Lesser Antilles is similar to other volcanic arcs
No evidence for subsurface fluid flow
Volcanism is confined to the region with high heat flow
Although a few historical tsunamis have occurred in the Lesser Antilles region, their characteristics are poorly documented due to the ephemeral nature of the associated signatures. Recently, a ...tsunami was generated following a magnitude Mw 6.3 earthquake that occurred on 21 November 2004 between Guadeloupe and Dominica. This was one of the two largest historical earthquakes recorded in this area in the last century. A field survey allowed us to characterize the tsunami which affected Les Saintes, the southern coast of Basse‐Terre (Guadeloupe) and northern Dominica. We used these data to constrain a numerical simulation of tsunami generation and propagation. The 21 November tsunami provides a unique opportunity to further constrain the models of brittle deformation in the back arc region proposed by previous tectonic investigations, to characterize the tsunami signatures and to improve regional hazards evaluation.
The Indonesian Young Toba Tuff (YTT), classically dated around 74 ka BP, is considered as a short-lived explosive cataclysmic super-eruption. The huge amounts of ash and SO
emitted are likely to have ...triggered a volcanic winter which accelerated the transition to the last glaciation, and may have induced a human genetic bottleneck. However, the global climatic impact of the YTT or its duration are hotly debated. The present work offers a new interpretation of the Toba volcanic complex eruptive history. Analysing the BAR94-25 marine core proximal to the Toba volcanic center and combining it with high-resolution tephrostratigraphy and δ
O stratigraphy, we show that the Toba complex produced a volcanic succession that consists of at least 17 distinct layers of tephra and cryptotephra. Textural and geochemical analyses show that the tephra layers can be divided in 3 main successive volcanic activity phases (VAP1 to VAP3) over a period of ~ 50 kyr. The main volcanic activity phase, VAP2, including the YTT, is likely composed of 6 eruptive events in an interval whose total duration is ~ 10 ka. Thus, we suggest that the eruptive model of the Toba volcano must be revised as the duration of the Toba volcanic activity was much longer than suggested by previous studies. The implications of re-estimating the emission rate and the dispersion of ashes and SO
include global environmental reconstitutions, climate change modelling and possibly human migration and evolution.
The past history of recurrent flank collapses of la Soufriere volcano of Guadeloupe, its structure, its well-developed hydrothermal system and the current activity constitute factors that could ...promote a future flank collapse, particularly in the case of a significant increase of activity, with or without shallow magmatic input. To address the hazards associated with such a collapse, we model the emplacement of the debris avalanche generated by a flank-collapse event in 1,250 BC (3,100 years B.P.). We use a finite-difference grain-flow model solving mass and momentum conservation equations that are depth-averaged over the slide thickness, and a Coulomb-type friction law with a variable basal (minimum) friction angle. Using the parameter values determined from this simulation, we then simulate the debris avalanche which could be generated by a potential collapse of the present lava dome. We then discuss the region which could be affected by such a future collapse, and additional associated hazards of concern.
•Lavas erupted offshore Mayotte since May 2018 are evolved basanites (∼5 wt% MgO).•The eruption is fed by a deep (>37 km) mantle reservoir.•Primitive magma has undergone at least 50% of ...crystallization in a ≥10 km3 mantle reservoir.•Magma transfer rate shows that the eruption is steadily supplied from the deep mantle reservoir.•After May 2019, ascending magma intersected a more evolved and shallower magma reservoir.
Deep-sea submarine eruptions are the least known type of volcanic activity, due to the difficulty of detecting, monitoring, and sampling them. Following an intense seismic crisis in May 2018, a large submarine effusive eruption offshore the island of Mayotte (Indian Ocean) has extruded at least 6.5 km3 of magma to date, making it the largest monitored submarine eruption as well as the largest effusive eruption on Earth since Iceland's 1783 Laki eruption. This volcano is located along a WNW-ESE volcanic ridge, extending from the island of Petite Terre (east side of Mayotte) to about 3,500 m of water depth. We present a detailed petrological and geochemical description of the erupted lavas sampled by the MAYOBS 1, 2, and 4 cruises between May and July 2019 and use these to infer characteristics and changes through time for the whole magmatic system and its dynamics from the source to the surface. These cruises provide an exceptional time-series of bathymetric, textural, petrological, and geochemical data for the 2018-2019 eruptive period, and hence bring an invaluable opportunity to better constrain the evolution of magma storage and transfer processes during a long-lived submarine eruption. Integrating the petrological signatures of dredged lavas with geophysical data, we show that the crystal-poor and gas-rich evolved basanitic magma was stored at mantle depth (>37 km) in a large (≥10 km3) reservoir and that the eruption was tectonically triggered. As the eruption proceeded, a decrease in ascent rate and/or a pathway change resulted in the incorporation of preexisting differentiated magma stored at a shallower level. Magma transfer from the deep mantle reservoir is syn-eruptive, as indicated by transfer times estimated from diffusion in zoned olivine crystals that are much shorter than the total eruption duration. Our petrological model has important hazard implications concerning the rapid and stealthy awakening of a deep gas-rich magma reservoirs that can produce unusually high output rates and long-lived eruption. Sudden tapping of large crystal poor reservoirs may be the trigger mechanism for other rarely witnessed high-volume (>1 km3) effusive events.
Marine tephrochronology provides a good alternative to study the eruptive history of volcanic islands and overcome the problem of poorly preserved on-land outcropping. Here, we provide new ...observations on the recent volcanological evolution (<40 kyrs) of Montagne Pelée (Martinique, Lesser Antilles) based on the tephrochonological study of a marine core from Site U1401, sampled during IODP Expedition 340 and located 28 km from the coastline, west off Martinique Island. The core (15 m recovered length) was obtained on the top of the debris avalanche deposits due to the last flank collapse that occurred on Montagne Pelée volcano. Although it was not possible to drill through the debris avalanche deposits because of the heterogeneity of the deposit and the presence of large blocks, the sediments and volcanic deposits that covered the debris avalanche deposits were sampled. A detailed multiparameter study (geophysical data acquired on-board during the IODP cruise, lithological and geochemical data and temporal constrains through 18O stratigraphy and 14C dating) of the core U1401A provides a new age for the last flank collapse leading us to update the recent volcanological history of Montagne Pelée. The last flank collapse is now dated at ~36 cal. ka BP (older than previous studies). The flank collapse, even though relatively minor in volume (2 km3), had a significant consequence on the magma plumbing system of Montagne Pelée and produced abundant explosive eruptions of basaltic-andesite magmas, during the period 36–25 cal. ka BP. This new age range obtained for this flank collapse has important implications for the post collapse activity and allows us to rethink the recent volcanological history of Montagne Pelée.
•Marine tephrochronology provides a good alternative to study the eruptive history of volcanic islands•The core U1401A (IODP Expedition 340) provides a new age for the last flank collapse, now dated at ~36 cal. ka BP.•The data allow us to update the volcanological recent history of Montagne Pelée.•This flank collapse has implications for the post collapse activity in terms of magmatology and magma production rate.
A horseshoe‐shaped structure already identified on the southwestern flank of Montagne Pelée (Martinique, Lesser Antilles arc) was previously interpreted as resulting of a flank collapse event, but no ...debris avalanche deposits were observed at the time. New offshore high‐resolution bathymetry and geophysical data (Aguadomar cruise; December 1998 to January 1999; R/V L'Atalante) lead us to identify three debris avalanche deposits on the submarine western flank of Montagne Pelée extending down to the Grenada Basin. They display morphological fronts and hummocky morphology on bathymetric data, speckled pattern on backscatter data and hyperbolic facies on 3.5 kHz and seismic profiles. New on‐land geological studies lead us to identify two other horseshoe‐shaped structures on the same flank of the volcano. The three submarine deposits have been traced back to the structures identified on land, which confirms the occurrence of repeated flank collapse events during the evolution of Montagne Pelée. The ages of the last two events are estimated at ∼9 ka and ∼25 ka on the basis of 14C and 238U/230Th dates. Every flank collapse produced debris avalanches which flowed down to the Caribbean Sea. We propose that the repeated instabilities are due to the large asymmetry of the island with western aerial and submarine slopes steeper than the eastern slopes. The asymmetry results from progressive loading by accumulation of volcanic products on the western slopes of the volcano and development of long‐term gravitational instabilities. Meteoric and hydrothermal fluid circulation on the floor of the second flank collapse structure also creates a weakened hydrothermalized area, which favors the recurrence of flank collapses.
Marine tephrochronology provides a good alternative to study the eruptive history of volcanic islands and overcome the problem of poorly preserved on-land outcropping. Here, we provide new ...observations on the recent volcanological evolution (<40 kyrs) of Montagne Pelée (Martinique, Lesser Antilles) based on the tephrochonological study of a marine core from Site U1401, sampled during IODP Expedition 340 and located 28 km from the coastline, west off Martinique Island. The core (15 m recovered length) was obtained on the top of the debris avalanche deposits due to the last flank collapse that occurred on Montagne Pelée volcano. Although it was not possible to drill through the debris avalanche deposits because of the heterogeneity of the deposit and the presence of large blocks, the sediments and volcanic deposits that covered the debris avalanche deposits were sampled. A detailed multiparameter study (geophysical data acquired on-board during the IODP cruise, lithological and geochemical data and temporal constrains through 18O stratigraphy and 14C dating) of the core U1401A provides a new age for the last flank collapse leading us to update the recent volcanological history of Montagne Pelée. The last flank collapse is now dated at ~36 cal. ka BP (older than previous studies). The flank collapse, even though relatively minor in volume (2 km3), had a significant consequence on the magma plumbing system of Montagne Pelée and produced abundant explosive eruptions of basaltic-andesite magmas, during the period 36–25 cal. ka BP. This new age range obtained for this flank collapse has important implications for the post collapse activity and allows us to rethink the recent volcanological history of Montagne Pelée.
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