Piton de la Fournaise: the volcano calms down, the eruption averted?


Piton de la Fournaise: the volcano calms down, the eruption averted?

PITON DE LA FOURNAISE ERUPTION. The prefecture of Reunion warned Monday of a probable next eruption of Piton de la Fournaise and triggered level 1 of the alert phase, a stage called "probable or imminent eruption". However, a return to calm was observed on Tuesday.

[Updated October 19, 2021 at 07:42] Should Reunionese prepare for a new eruption of Piton de la Fournaise? Caution is required, but the risk receded a little on Tuesday with the observed decline in the activity of the volcano. The seismic crisis, which began Monday, October 18 at 4:33 a.m. local time, has weakened. The Volcanological Observatory of Piton de la Fournaise still notes rare earthquakes very localized to the west of Piton de Crac but the alert seems to be receding.

The level 1 alert triggered on Monday October 18 by the island's prefect, following a communication from the Volcanological Observatory of Piton de la Fournaise confirming the start of a seismic crisis, recorded at 4:33 a.m. on Monday October 18 according to a press release reported by La 1ere, however, remains in force. "Between 4:33 a.m. and 4:00 p.m., 627 volcano-tectonic earthquakes and 176 long-period type earthquakes were recorded," the Piton de la Fournaise volcanological observatory (OVPF) said on Monday.

This alert was followed by an official communication from the prefect of La Réunion who announced the triggering of alert phase 1 called "probable or imminent eruption" from 7 a.m. on Monday. This stadium restricts access to the site by prohibiting the use of paths such as the Pas de Bellecombe and those leading to the upper part of the Piton de la Fournaise enclosure. It is recalled that the "landing of aircraft in the volcano area is regulated and subject to authorization by the prefecture" notes the prefect.

The inhabitants of Reunion Island were invited to prepare for a new imminent eruption since the Volcanic Observatory of Piton de la Fournaise mentioned in its alert of Monday October 18 a "probable eruption in the short term in the next few minutes or hours". Later in the morning, the Observatory gave more details, listing 537 volcano-tectonic earthquakes between 4:33 a.m. and 10:50 a.m. local time, activity located under the "summit zone and under the eastern flank". The area affected by the migration of magma to the surface will be the north and northeast flank of Piton de la Fournaise, at Piton de Crac.

The observatory thus notes that the sector is "a little further north than the intrusion of September 28-30, 2020. In 2020, the seismic crisis, which had accompanied this intrusion, had lasted two days and had not led to any an eruption, the magma having stopped at depth." Can an eruption therefore be avoided? Yes, but the Observatory recalls that "the longer the seismic crises, the greater the risk of opening eruptive cracks at low altitude increases."

The last eruption of Piton de la Fournaise dates from last May, recalls La 1ere. Scientists then announced a probable new eruption by the end of 2021. However, the Observatory has observed an increase in activity of the volcano since September 20 with no less than 52 earthquakes recorded in one month and above all 12 earthquakes on Monday 11 October alone. This activity has led to an increase in underground pressure. The area has therefore been particularly scrutinized in recent hours, especially since Reunion is to host Le Grand Raid this week, including the famous "Diagonale des Fous", the legendary trail whose start for the 2021 edition is scheduled for this Thursday, October 21.