Recent studies have shown that giant landslides correlate with climatic variations. However, the precise processes involved in this phenomenon need to be better defined. This study investigates the ...causes of giant landslides using a modeling approach. Here, I show that the effect of meteoric water infiltration could be distinguished from that of the sea level rise in triggering paleo-landslides. It is possible to identify the cause of coastal paleo-landslides based on the age of occurrence and comparison with climatic signals when glacial maxima are wetter than during interglacial periods, as in Polynesia and East Equatorial Africa, but not in other cases (Caribbean, Indonesia). The role of pore-pressure variations and sea water loading variations is discussed. The interaction between the relative sea level rise, pre-existing relief and deep weak structure due to the presence of highly weathered lavas may trigger the conditions for a large landslide. Highly weathered lavas have very low friction angles in volcanic islands. When volcanoes are still active, pressure fluctuations in the magma chamber caused by sea level lowering are expected to play a significant role in the destabilization of the relief. Competing processes in real cases make it difficult to distinguish between these processes.
Intraplate volcanic islands are often considered as stable relief with constant vertical motion and used for relative sea-level reconstruction. This study shows that large abrupt mass unloading ...causes non-negligible isostatic adjustment. The vertical motion that occurs after abrupt mass unloading is quantified using a modeling approach. We show that a giant landslide causes a coastline uplift of 80–110 m for an elastic thickness of 15 km < Te < 20 km in Tahiti. Theoretical cases also reveal that a coastal motion of 1 m occurs for an abrupt mass unloading involving a displaced volume of 0.2 km3 and influences relative sea-level reconstruction. In Tahiti, a change in the subsidence rate of 0.1 mm/yr (from 0.25 to 0.15 mm/year) occurred during the last 6 kyr and could be explained by an abrupt mass unloading involving a minimum volume of 0.2 km3, 6 ± 1 kyr ago.
During the last 10 kyr, significant subsidence and uplift occurred on Mayotte Island in the Comoros archipelago (Indian Ocean), but the role of volcanic processes in Holocene vertical movements has ...been neglected in the research so far. Here, we show that an abrupt subsidence of 6–10 m occurred between 9.4 and 10 kyr ago, followed by an uplift of the same amplitude at a rate of 9 mm/yr from 8.1 to 7 kyr ago. A comparison of the relative sea level of Mayotte and a reference sea level curve for the global ocean has been conducted using a modeling approach. This shows that an increasing and decreasing pressure at depth, equivalent to the process caused by a deep magma reservoir (50–70 km), was responsible for ~6–10 m subsidence and 6–10 m uplift, whereas loading by new volcanic edifices caused subsidence during the last few thousand years. Surface movements and deep pressure variations may be caused by pulses from the deep mantle, related to superplume activity, but uncertainties and unknowns about these phenomena are still present and further studies are needed. A better understanding of the volcano-tectonic cycle may improve assessments of volcanic hazards.
Relative sea level records climatic change as well as vertical land movement. In Barbados, uplift variation is necessary to interpret one of the most complete coral reef records. Here we show that an ...abrupt mass unloading of 30 ± 10 km3 caused an uplift variation of ~0.45 ± 0.15 mm/yr using a modelling approach. Simulations have been conducted for different volumes and elastic thicknesses. Isostatic adjustment in relation with an abrupt mass unloading explains the observed uplift rate increased from 0.34 mm/yr to 0.8 mm/yr that occurred 11.2 kyr ago. The reconstructed sea-level curve highlights a sea-level jump of 4.8 m, with a delay of 150 yr from the termination of Younger Dryas cold event and 300 yr before the abrupt mass unloading. This sea-level jump corresponds to meltwater pulse MWP-1B and is not an artefact. A stagnation of 500 yr occurred from 12 to 11.5 kyr BP. Relative sea level records are useful to detect past landslides and erosion. Accurate analysis and reconstruction of sea-level permits to determine sea-level abrupt rise caused by climate warming during the last thousand years.
Geographic and geological context. (A) Location of Barbados Island in the red square, (B) Geological map and bathymetry of Barbados Island, (C) Schematic representation of mass unloading and lithosphere geometry. Bathymetry from https://www.ncei.noaa.gov/maps/bathymetry, (D) Sea Level at different ages from Tahiti coral reefs data in red (Bar et al., 2010) corrected from a subsidence of 0.25 mm/yr and Barbados coral reefs data (Peltier and Fairbank, 2006; Abdul et al., 2016) with a correction of 0.8 mm/yr after 11.2 kyr in light blue (Abdul et al., 2016) and dark blue (Peltier and Fairbank, 2006) and 0.34 mm/yr before 11.2 kyr in green (Peltier and Fairbank, 2006) and pink (Abdul et al., 2016). Display omitted
•An abrupt mass unloading of 30 ± 10 km3 occurred in Barbados and caused isostatic adjustment of 0.45 ± 0.15 mm/yr.•An uplift increases from 0.34 to 0.8 mm/yr at 11.2 kyr BP in less than 0.2 kyr explain coral reef elevation in Barbados.•150 yr after the Younger Drias and 300 yr before the abrupt mass unloading, a sea-level jump of 4.8 m occurred.
Runout distance was used here to determine whether the large landslide deposit formed several thousand years ago in northern Tahiti was caused by a single or multiple events. Using modelling to ...quantify the dynamics of this event suggested that a single event or a small number of events (n < 10) were responsible, and that the maximum slide velocity was high (>125 m/s) under partially submarine conditions. Such submarine propagation favoured a slower dynamic but a longer runout. The effective basal friction under submarine conditions ranged from 0.2 < μ < 0.3.
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•One or a few landslide events created the large scar and mass deposits in Tahiti.•Peak slide velocity reached 125–250 m/s.•The high mobility related to an effective basal friction of 0.2–0.3 under submarine conditions
Relative sea level records climatic change as well as vertical land movement. In Barbados, uplift variation is necessary to interpret one of the most complete coral reef records. Here we show that an ...abrupt mass unloading of 30 ± 10 km 3 caused an uplift variation of ~0.45 ± 0.15 mm/yr using a modelling approach. Simulations have been conducted for different volumes and elastic thicknesses. Isostatic adjustment in relation with an abrupt mass unloading explains the observed uplift rate increased from 0.34 mm/yr to 0.8 mm/yr that occurred 11.2 kyr ago. The reconstructed sea-level curve highlights a sea-level jump of 4.8 m, with a delay of 150 yr from the termination of Younger Dryas cold event and 300 yr before the abrupt mass unloading. This sea-level jump corresponds to meltwater pulse MWP-1B and is not an artefact. A stagnation of 500 yr occurred from 12 to 11.5 kyr BP. Relative sea level records are useful to detect past landslides and erosion. Accurate analysis and reconstruction of sea-level permits to determine sea-level abrupt rise caused by climate warming during the last thousand years.
The Mediterranean Basin has not always been connected to the Atlantic Ocean. During the Messinian salinity crisis (MSC), the Mediterranean Sea became progressively isolated by a complex combination ...of tectonic and glacio‐eustatic processes. When isolated, the Mediterranean water level depends on the hydrological flux and is expected to vary significantly. The amplitude and number of large water level fluctuations in the isolated Mediterranean is still controversial, despite numerous geological investigations. The observation of 3–5 surfaces of erosion in the Nile delta (Eastern Basin) provides new elements for understanding the dynamics of the MSC. Our model demonstrates that numerous water level falls of short duration may explain the preservation of a discontinuous river profile at ∼−500 m and ∼−1500 m in the Western Basin, as well as the existence of deep surfaces of erosion in the Eastern Basin.
Le colloque « Vérités scientifiques et enjeux sociaux » a permis de nourrir une réflexion sur l’organisation des sciences en lien avec la production des preuves scientifiques et leurs modes de ...partage. Comment faire émerger la diversité des enjeux sociaux dans les sciences ? Comment partager plus largement la production scientifique et celle des preuves ? Les modes de production, de validation et de partage des preuves ne sont pas figés, ce qui les rend difficiles à appréhender. Les écueils et les mécanismes favorisant la fabrication de l’ignorance ont ainsi été abordés. L’interdisciplinarité, les sciences inclusives et les synthèses scientifiques collectives, thèmes évoqués lors du colloque, sont autant de pistes pour éclairer les débats publics, partager autrement les preuves et la capacité d’expertise, et définir collectivement les enjeux.
Recovery and inequality growth after a disaster are often difficult to estimate. In this study, specific indicators were developed to analyze recovery and inequality growth. Here we show that after a ...major disaster the difference in recovery between two territories causes inequality growth. Energy production is relevant for describing variations in social and economic activities. This indicator was applied to a case study of a natural disaster, that is Hurricane Irma in 2017. The hurricane caused fatalities and destruction in the Caribbean islands of Saint Martin and Saint Barthelemy, which are two French overseas territories. Energy production after Hurricane Irma exhibited a significant decrease due to the destruction of the electricity network as well as perturbations in economic and social activities. The energy production restoration rate was faster in Saint Barthelemy than in Saint Martin. The energy production 18 months after Hurricane Irma was identical to that before Hurricane Irma in Saint Barthelemy, whereas this was not the case in Saint Martin. During recovery, an increase in the gap between energy production in Saint Barthelemy and Saint Martin was observed. This gap represents an inequality growth between Saint Barthelemy and Saint Martin. The indicators emphasized that the wealthier territories recover faster than the less wealthy and that natural disasters favors inequality growth. Inequality growth is expected to occur with natural disaster development. The number of inhabitants must be considered during indicator construction to avoid any bias.
•Recovery after Hurricane Irma was faster in Saint Barthelemy (wealthier) than in Saint Martin.•Migration of thousands of inhabitants outside Saint Martin reduced electricity production and economic activity.•Energy production could be used for monitoring inequality growth after disasters.•Natural disasters could cause inequality growth of 15–20% per event between territories during recovery.
After major hurricanes, electricity production reduced owing to not only electricity infrastructure destruction, but also the economic crisis associated with damage to private and public activities. ...Here, we describe the electricity production curves for the islands of Saint-Martin, Saint-Barthelemy and Puerto Rico in the Caribbean, where two major hurricanes occurred in 2017. After the major hurricanes, the electricity energy production was characterised by a slow recovery followed by a stable phase during several months, corresponding to approximately 75% of the initial electricity production. A resilience time of several months (1 month < ts < 5 months) is necessary to attain the new electricity energy production equilibrium Eis, which is lower than the initial electricity energy production Ei. The reduction in electricity energy consumption per capita is of 25%. In Saint-Martin, during the post-hurricane stable phase, the electricity production was only 60% of the initial electricity energy production instead of 75%. The reduction of ∼15% in the electricity production of Saint-Martin after Hurricane Irma is attributed to the migration of approximately 8000 inhabitants (approximately 23%) outside the island. This approach makes it possible to anticipate the production of electricity during several months after a major hurricane in the Caribbean islands and to evaluate population displacement.
•After major hurricanes, electricity energy production is characterised by a slow recovery.•A stable phase corresponding to ∼75% of the initial electricity production can be observe.•St-Barth, St-Martin and Puerto-Rico electricity productions after major hurricane have been simulated.•Simulations show that 8000 inhabitants left the French Caribbean island of Saint-Martin after hurricane Irma.
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