The explosion at 4:20 a.m. on September 20 at Sangay was the most significant event in recent months.
Within 10 minutes, several satellite images showed a large cloud of ash rising 6 to 10 km above the summit; The high altitude portions of the cloud drifted east while the lower portions drifted west. Thirty-two districts in the provinces of Chimborazo, Bolívar, Guayas and Los Ríos were affected by ash fall. Authorities in the Bucay and Cumandá districts restricted the conduct, opening of businesses and outdoor activities due to the ash fall. Guayaquil's José Joaquín de Olmedo Airport has suspended operations for seven hours to clean the runways. Ashfall was most severe in Chimborazo, particularly in the districts of Guamote, Alausí, Chunchi, Pallatanga and Cumandá, with photos showing poor visibility and ashfall covering streets, cars and homes. Ashfall had a significant impact on agricultural fields.
Authorities inspected the confluence of the Volcán River (SE flank) and the Upano River, and observed significant deposits of tephra, some of which had sealed off the river and created a huge lagoon. Normally the Upano was about 25m wide in this area, but because of the deposits it was over 250m across and had almost no water in it. After the explosion, IG noted that activity returned to levels similar to previous months with ash plumes rising 1 to 2 km above the volcano from September 20 to 22.
From Sunday 20 to Wednesday 23 September this year, a group of researchers from the Geophysical Institute of the National Polytechnic School (IGEPN) and the French Institute for Research for Development (IRD) visited the provinces of Chimborazo, Cañar and Guayas. During this visit, the technicians measured the gas flow, took ash samples, gave explanations to local authorities and maintained the stations of the volcano monitoring network.
Source: IGEPN & GVP
In Guatemala, the constant rains on the volcanic complex of Fuego generated a moderate lahar in the barranca of the rio Ceniza, a tributary of the rio Achiguate; it is made of fine materials, branches and tree trunks and blocks between 30 cm and 1.5 m. of diameter.
Other lahars could form in the other barrancas, the volcanic deposits being saturated with water.
This September 23, the pattern of activity remains the same as the previous days, with weak to moderate explosions, at a rate of 12 to 18 per hour, accompanied by columns of ash reaching 4,700 meters asl. Constant avalanches from the edge of the crater are observed in the direction of the many drainages. Ash falls are reported in the areas of Panimache, Morella, Santa Sofia, Porvenir, Yucales, Sangre de Cristo and San Pedro Yepocapa.
Since September 20, a resumption of seismicity has been observed under the Piton de la Fournaise.
Between September 20 and 22, 21 earthquakes, of magnitude less than or equal to 1, were recorded and located under the Dolomieu crater between 1.7 and 2.2 km deep.
This seismicity is accompanied by a resumption of inflation (swelling) of the base and top of the Piton de la Fournaise building. This building inflation remains very low for the time being and will need to be confirmed over time over the next few days.
This seismicity and deformation are synonymous with a pressurization of the superficial magmatic reservoir located about 2-2.5 km below the summit.
Piton de La Fournaise - Histogram representing the number of superficial volcano-tectonic earthquakes recorded since September 1, 2020 (© OVPF-IPGP).
Location map (epicenters) and north-south and east-west sections (showing the location in depth, hypocenters) of earthquakes recorded and located by the OVPF-IPGP between September 20 and 22, 2020 under the Piton de la massif. Furnace. Only localizable earthquakes have been shown on the map (© OVPF-IPGP)
Soil CO2 fluxes also show a trend reversal since mid-August. After a long continuous phase of reduction of CO2 emissions in the soil following the last eruption (April 2-6, 2020), a new phase of increase has been observed since mid-August and has continued since. This increase in far-field CO2 is consistent with a deep rise in magma.
At the same time, the SO2 fluxes recorded in the air remain below the detection threshold. The concentrations of H2S and SO2 in the fumaroles in the summit area remain low and despite a slight tendency to increase the concentration of So2 since August 2020, the concentrations are extremely low.
Note that this process of recharging the surface reservoir can last several days to several weeks before the roof of the reservoir weakens and breaks, thus giving rise to an injection of magma to the surface and an eruption, but can also stop without giving rise to an eruption in the short term.
Find all the information relating to the activity of Piton de la Fournaise on the various media of the OVPF-IPGP:
- the website (http://www.ipgp.fr/fr/ovpf/actualites-ovpf),
- the Twitter account (https://twitter.com/obsfournaise?lang=fr),
- and the facebook account (https://www.facebook.com/ObsVolcanoPitonFournaise/)