A new volcano near Mayotte

Although it is a popular tourist destination, most of you will not know that Mayotte is an island in the Indian Ocean. It is part of France as an overseas department and region. While geographically a part of the Comoros archipelago, located off the coast of Southeast Africa, it is politically not part of it.

Mayotte consists of two islands, Maore (or in French Grande-Terre), the smaller Pamanzi (or in French Petite-Terre) and some smaller islets scattered around the main islands.

The archipelago is a primarily volcanic, rising steeply from the bed of the ocean to a height of 660 metres. Two volcanoes are looming on the main island; the Pic Chongui in the south and Mont M'Tsapéré in the north. Both are dormant and the last eruption is thought to have occurred some 7,000 years ago.

The quiescence of the islands was rudely disturbed on May 10th, 2018 with a series of earthquakes. A magnitude-5.8 earthquake, the largest ever recorded in the Comoros basin, struck just off the coast five days later. A research programme was carried out to try to understand the origin of those quakes. The research focused on a nascent underwater volcano discovered in May 2019, some 50 kilometres east of the island of Mayotte and at a depth of 3,500 meters.

The research mapped the volcanic ridge between the active volcano and the seismic zone (about 15 kilometres from the island). Seismic activity has now decreased.

The data collected confirms that the height of the volcano has not changed (its peak is at a depth of 2,850 meters). On the other hand, since June 2019, a new lava flow has been identified on the western flank of the underwater volcano. It is more than 150 metres thick. Its estimated volume is 0.3 square kilometres.

The undersea volcano was spewing volcanic material to a height of two kilometres, but the lava could not reach the surface of the ocean. The volcano is linked to a rapid rate of shifting and sinking of Mayotte. The sinking on the island’s east end has reached 13 centimetres since July 2018.

The volcano and the sinking of the island could herald death and destruction. The meaning of its local (and original) name of Maore was almost prophetic, because the name is believed to originate from Arabic Jazīrat al-Mawt (جزيرة الموت), meaning 'island of death'. Although some speculate that the name was chosen because of the dangerous reefs that surround the islands.