A volcanic monster has been growing under the waters of the Pacific Ocean for 120 million years!

Volcanic eruptions are a daily occurrence on Earth. On the continents, volcanic activity cannot go unnoticed, and most of the time it is the subject of great interest, either because it directly threatens the population, or simply to enjoy the spectacle of the wonderful forces of nature in action.

A volcanic plateau whose surface area reaches 40% of the area of ​​mainland France

The oceanic world also experiences its share of explosions. In fact, the ocean floor is dotted with numerous volcanoes, some of which easily rival those we encounter on Earth in size and power. Far below the surface, massive volcanic episodes occur, without us really realizing it. For 120 million years, there has been a massive lava flow forming at the bottom of the Pacific Ocean. It's about Melanesian border plateau. This superstructure of volcanic origin, near the Solomon Islands, extends approximately 222 thousand kilometers²Which represents 40% of the French mainland! Clearly, his growth is not over yet.

The story of tectonic drift

The origin of this vast volcanic plateau has been a mystery until now. Was it formed all at once or in several episodes? However, in 2013, a team of scientists conducted a series of dredging operations to better understand its history. Published this year in the magazine Earth and planetary sciences lettersThe results of the analysis revealed that it formed gradually over the past 120 million years, during 4 main pulses of volcanic activity associated with very different geodynamic processes. The first stage seemed to be particularly dramatic, with the lava flow BasalticBasaltic Of large size. With time and thanks a movementa movement From the Pacific plate, this proto-plateau had gradually moved until, 45 million years ago, it found itself above a hotspot called Ruruto-Arago.

Intense volcanic activity would have created a chain of volcanic islands above the plateau. Eventually, these islands will be overcome by erosion, which will gradually disappear under the water, as the Pacific plate continues its migration. Thus, the plateau, which was thickened by recent events, found itself on top of another 13 million years ago connection pointconnection pointthe same person who is currently participating in buildingbuilding From the Samoan Islands. New islands form, only to disappear over time.

But the story of the plateau is not over yet. Her tectonic journey finally brought her to a level SubductionSubduction From the Tonga Islands. This is where the Pacific plate sinks into the Earth's mantle to be recycled. This geodynamic context also produces volcanic activity, which will be added to and participate in the construction of the pre-existing plateau.

Thus, this study reveals the complex history of this vast oceanic plateau, and demonstrates the extent to which its formation was discontinuous and linked to multiple magmatic processes, linked to the movement of the Pacific Plate.