Rapid Response for on-land Volcanic Hazard Assessment during the 2018-2019 submarine Mayotte Volcano-tectonic Crisis: Implications for Volcanic Risk Quantification.
Abstract
Mayotte is the most easterly and oldest of the Comoros islands, well known for the activity of the basaltic Karthala volcano, which is located on the opposite, westernmost and youngest end of the archipelago. In spite of being considered dormant since at least 4 kyrs, the eastern submarine slopes of Mayotte are, since 2018, the site of one of the largest eruptions on Earth since that of Laki. The still on-going volcano tectonic event consists of an exceptionally long-lasting, intense and voluminous volcano-tectonic crisis, with hundreds of unusually strong VT events (M: 3.5-5.5) recorded and the emission on the sea floor (ca 3.5 km bsl) of several km3 of tephrite lava, building an outstanding submarine volcanic cone (800 m high) and a large lava field. During the crisis, we focused on the most recent subaerial volcanic activity documented at Petite Terre, the second largest island of Mayotte, which is densely inhabited (30.000 habitants) and the site of the only airport of the island. The subaerial activity occurred on the coral reef and represents the potential on land extension of a regional WNW-ESE oriented volcanic ridge, whose subaqueous part is the site of the 2018-2019 activity. We document a bimodal volcanic activity, in terms of both magma composition (tephrite and phonolite) and explosivity. The most explosive events (phonolitic) produced a range of eruptive dynamics spanning from widely dispersed, short-lived ash and lapilli fallout, energetic dilute pyroclastic density currents and ballistic projections, which blocks of basalts and corals more than 1 m in diameter. This activity built a set of phonolite maars with a global N-S dispersion along the eastern coast of Petite Terre. In contrast, the mafic magma (tephrite) built scoria cones and moderate volumes of lava that occurred on the western side of Petite Terre. Some of these cones are aligned with areas of important CO2-rich soil emissions. Part of the mafic scoria cones are covered by phonolitic tephra. We here discuss the potential genetic link between mafic and evolved magma end-members, their similarities and differences with volcanic products dredged along the subaqueous rift and discuss the implications in terms of time evolution of magma storage, magma ascent, eruption trigger and dynamics.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.V33A..02B
- Keywords:
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- 3275 Uncertainty quantification;
- MATHEMATICAL GEOPHYSICS;
- 8419 Volcano monitoring;
- VOLCANOLOGY;
- 8488 Volcanic hazards and risks;
- VOLCANOLOGY;
- 8494 Instruments and techniques;
- VOLCANOLOGY