Mayotte: how was the island formed?

FROM THE BIRTH OF MAYOTTE TO TODAY 

Mayotte is located in the northern part of the Mozambique Channel. Its history is associated with the two continental masses of Madagascar and Africa. If you cut into the Earth, you would see a succession of solid and liquid layers affected by flows of heat and matter that are expressed on the surface by the movement of continents. 180 million years ago, when dinosaurs roamed the Earth, Madagascar separated from Africa and migrated to the southeast. Over 100 million years, Madagascar traveled 1,500km. Thousands of meters underwater, cracks in the Earth's crust allowed lava to cover the ocean floor. On contact with the water, the lava hardened. The lava accumulated little by little to form underwater volcanoes. The Mayotte volcano was already 3,000m high when, around 10 million years ago, the first lava arrived on the water's surface. The new volcano rose to hundreds of meters above sea level. When lava stopped arriving at the water's surface, rain wore the slopes down and made them disappear. That was how Mayotte was built. Around 2 million years ago, volcanic activity began to slow down. Only the northern part of the island remained active. The geometry of the island as we know it today began to take shape with the formation of the coral reef. The last known aboveground volcanic events occurred 10,000 years ago, in what are now Mtaspéré, Digo and Petite-Terre. It was 9,000 years later that the first humans came to Mayotte. In 2018, on the eastern side of the island, a new, small underwater volcano formed. In the south, Choungui mountain rises to 594m. Originally, there was a much higher volcano. During the last eruption, the lava in the volcano's chimney hardened. Over time, erosion attacked the slopes, and the softer rocks were washed into the ocean. Those in the center of the volcano formed a residual slope that defines Choungui in its current form. Thousands of years from now, this geological object will remain as the only island in the lagoon. In the east, the coral reef ends abruptly, cut off by a channel called the "S pass," whose origin can be traced back to the island's recent history. Over the last 1.2 million years, the world's climate has changed, with successive periods of intense cold and heat. In the coldest times, the sea level fell dozens of meters. The lagoon was completely emptied and rivers carved into their banks. That was when the S pass formed. When the climate got warmer, the sea level rose, as it is doing now. On Petite-Terre, the Moya and Dziani volcanoes are where ancient craters appeared less than 780,000 years ago. These volcanoes resulted from the meeting of lava and water. They are phreatomagmatic volcanoes. With violent explosions, the rock was pulverized. Ashes, boulders and bombs fell around the crater. Over time, deposits accumulated around the explosion area. On Grande-Terre, the Kaweni and Cavani depressions resulted from the same phenomena. While the island's volcanoes had been dormant for thousands of years, on the night of May 10, 2018, the earth began to rumble. Earthquakes linked to volcanic activity originating over 20km underwater were the result of cracks forming and lava moving through the Earth's crust. The intensity and number of earthquakes reflected the rapid ascent of lava. In less than two months, it traveled 20km to form a new volcano at the bottom of the sea. The emptying of the magma chamber sunk the rocks above it. That subsidence reached its peak in July 2019. Since then, it has been gradually decreasing. In one year, an 800m volcano corresponding to 5 km3 of rock was born. For over 1,300 years, man has been learning to live in Mayotte. The island's rich landscapes, plants and animals are all linked to its volcanic origin, and the recent resumption of activity will help maintain them. Heightened monitoring of the Earth's activity is essential to keep an eye on the life of volcanoes and the consequences for mankind.