Relative Sea Level and Coastal Vertical Movements in Relation to Volcano-Tectonic Processes at Mayotte Island, Indian Ocean

Julien Gargani (1)

1 GEOPS - Géosciences Paris Saclay

During the last 10 kyr, significant subsidence and uplift occurred on Mayotte Island in the Com-oros archipelago (Indian Ocean) (Indian Ocean), but the role of volcanic processes in Holocene vertical movements has been neglected so far so far. Here, we show that an abrupt subsidence of 6-10 m occurred between 9.4 and 10 kyr ago and followed by uplift of the same amplitude at a rate of 9 mm/yr from 8.1 to 7 kyr ago. Comparison of the relative sea level of Mayotte and a ref-erence sea level curve for global ocean for global ocean has been conducted using a modeling approach. This shows that increasing and decreasing pressure at depth, equivalent to the one caused by a deep magma reservoir (50-70 km), in a deep magma reservoir (50-70 km) was re-sponsible 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 uncertainty are still present and further studies are needed but uncertainties and unknown about this phenomena are still presents and further studies are needed. A better understanding of the volcano-tectonic cycle may improve volcanic hazard and risk assessment.

Mots clés: Comoro Archipelago; volcano; sea level; uplift; subsidence; magma chamber; mantle plume; Mayotte; Isostatic adjustment; deformation; Plate boundary; Coast; Coral reef

Domaines: Volcanologie; Océanographie; Tectonique

Julien Gargani. Relative Sea Level and Coastal Vertical Movements in Relation to Volcano-Tectonic Processes at Mayotte Island, Indian Ocean. GeoHazards, 2024, 5 (2), pp.329 - 349. ⟨10.3390/geohazards5020017⟩. ⟨hal-04558066⟩