Volcano: two lava entries into the sea and waters above 40°C observed by scientists

Just hours before the end of the eruption of Piton de la Fournaise on Wednesday, March 25, 2026, a scientific mission was conducted off the lava flow. Initial observations by experts confirmed intense activity at the interface between the lava and the ocean, with two lava entries into the sea and water temperatures exceeding 40°C, opening new avenues for study (Photos Alain Barrère – Biolave – Volcano Observatory).

A significant amount of smoke was still rising when a multidisciplinary team of scientists approached the lava platform formed at the sea entrance, off Sainte-Rose. Geologists, geochemists, and specialists from the Biolave program conducted an initial reconnaissance of the area on board a semi-rigid boat.

– Volcanic plumes measured using a spectrometer –

Among them, researchers from the University of Lyon I and Clermont, as well as an Irish scientist, measured the composition of the volcanic plumes using a spectrometer. Atmospheric samples were also taken to analyze the particles and gases present in the air.

“We observed two main lava outlets with strong plumes,” explained scientist Alain Barrère, involved in the Biolave program. The plume mainly consists of water vapor, hydrochloric acid (HCl), and fine particles. This plume, sometimes referred to as “laze” (lava haze), can be irritating and corrosive to the respiratory tract, skin, and eyes, with dispersion depending closely on local weather conditions.

– Very hot water outlets discovered –

At sea, these entry points appear to be associated with marked underwater phenomena. “We found two very hot water channels, over 40°C, likely linked to underwater leaks,” added Alain Barrère. Water samples were also taken along a perpendicular axis to the platform to refine the analyses.

When the lava plunged into the ocean, it caused a thermal shock of over 1,150 degrees, partially heating the ocean for about twenty meters off La Réunion. “This encounter resulted in a small black sand beach downstream of the ash,” said Nicolas Villeneuve, lecturer at the University of La Réunion and member of the Piton de la Fournaise Volcanological Observatory.

– Documenting a rare phenomenon –

In addition to scientific measurements, the mission also aimed to visually document this volcanic event. Teams from the Volcano Observatory, the Center for Volcanism Documentation and Dissemination, and Alain Barrère were present to capture images and records.

These observations complement ongoing research since the start of the eruption, particularly on the interactions between lava and the marine environment. While no phenomenon similar to the 2007 event, where deep-sea fish were brought up, has been observed so far, scientists remain vigilant.

As the eruption nears its end, the data collected during this mission should provide a better understanding of these spectacular interactions at the heart of Reunion Island’s volcanism. Stay updated on volcano news here.

Volcano, Piton de la Fournaise, Biolave Mission, Lava Flow, Atmosphere, Gas