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Discovery of the birth of a new underwater volcano to the east of Mayotte

Interministerial press release - Discovery of the birth of a new underwater volcano to the east of Mayotte: improving our knowledge and preventing risks

Discovery of the birth of a new underwater volcano to the east of Mayotte

Publication date: 16/05/2019

General public, Observatories, Press, Research

Related themes : Natural Hazards

The discovery of this volcano, located 50 km to the east of the island at a depth of 3,500 m, provides a better understanding of the earthquakes that have been occurring on the island over the past year. In light of this discovery, the Government is fully mobilised to deepen and pursue its understanding of this exceptional phenomenon and to take the necessary measures to better characterise and prevent the risks it would represent.

Since May 2018, Mayotte has been experiencing a succession of seismic episodes and a major interministerial and scientific mobilisation has been put in place to understand this new phenomenon and put in place appropriate anticipation measures. As early as June 2018, the government took the initiative of launching a scientific mission involving, in particular, the oceanographic campaign carried out by the Marion Dufresne ship (due to return to dock in Mayotte on May 15th 2019), which is now shedding major light on these episodes.

Birth of an underwater volcano observed for the first time

The mission was led by the French National Centre for Scientific Research (CNRS), with the Bureau de recherches géologiques et minières (BRGM), the Institut de physique du globe de Paris (IPGP), the Institut français de recherche pour l’exploitation de la mer (IFREMER), the University of Reunion, the Institut de physique du globe de Strasbourg (IPGS), the Institut national de l’information géographique et forestière (IGN), the École normale supérieure (ENS), the Centre nationale d’études spatiales (CNES) and the Service hydrographique et océanographique de la marine (SHOM), which is adding land-based observations to the Marion Dufresne’s oceanographic campaign, has revealed a new underwater volcano, 50 km off Petite-Terre.

The new volcano is located at a depth of 3,500 m. Its current size is estimated at 800 m high with a base 4 to 5 km in diameter. The 2km-high plume of volcanic fluids does not reach the water’s surface. According to the mission, the gas emanations observed on the Petite-Terre coast by the local population are a usual sign of this type of volcanic activity and will be the subject of specific studies.

View towards Mayotte of the volcanic ridge and its many edifices. The new volcano is indicated by an arrow.

The reasons for the seismic phenomenon in Mayotte

The marine instrumentation deployed will help to better locate the seismic swarm felt since 2018.

Scientists are mobilised to process, analyse and interpret the multitude of data acquired over the last few months. This will require in-depth work to assess the risks to Mayotte in terms of seismic risk, volcanic risk and tsunami risk.

The study programme will then be updated and strengthened in the light of the new knowledge provided by these in-depth analyses.

A renewed and strengthened commitment from the State

Since the beginning of the earthquake phenomenon, the State has been continuously adapting its monitoring and prevention measures in the light of scientific findings, in order to deal with this exceptional geological phenomenon that is impacting the population of Mauritius and, more broadly, this part of the Indian Ocean.

In conjunction with the elected representatives and other players involved, the government has defined the following 5-point action plan:

  • Completing the monitoring systems and measuring instruments (such as seismographs and GPS beacons) as quickly as possible, so that the phenomenon can be tracked continuously;
  • Complete scientific knowledge through appropriate missions;
  • Immediately update our knowledge of the risks posed by this phenomenon and its potential impact on the island, the results of which could be presented within three months;
  • Immediately strengthen the crisis management planning and preparation system. To this end, a civil protection planning support mission has been dispatched to provide support to the Prefect (updating crisis management mechanisms such as ORSEC plans). It will be on site from Friday  17th May;
  • Keeping the public regularly informed, in conjunction with local elected representatives.

In addition, this new information will be shared internationally in the Indian Ocean region.

The government, its administration and the scientific community are fully mobilised to continue understanding this exceptional geological phenomenon. The deployment of the necessary measures to better characterise and prevent the risks that this new volcano could present for the population of Mayotte will be the subject of regular information.

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