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Earth of fire

Actualité volcanique, Articles de fond sur étude de volcan, tectonique, récits et photos de voyage

Publié le par Bernard Duyck
Publié dans : #volcanic activity

Over the past two weeks, a slight increase in surface eruptive activity has been observed in El Reventador volcano, Ecuador.

The activity is characterized by the generation of eruptive columns and pyroclastic density currents (or pyroclastic flows) generated from the crater of the volcano, which are preferentially directed towards its western, northern and northeastern flanks of the volcano, maintaining its deposits inside the amphitheater. This was confirmed by the presence of thermal anomalies on the eastern flank detected by the infrared camera located on the northeast flank, while thanks to satellite thermal sensors (FIRMS, MIROVA) it is possible to detect activity on the western flank. The heights of gas and ash emissions reach between 0.7 and 1.3 km above the level of the crater and extend for several kilometers to the northwest, west and southwest of the volcano.

 El Reventador - ash plume 500 m high on 07/16/2020 - photo Darwin Yánez, técnico SNGRE / via IGEPN

El Reventador - ash plume 500 m high on 07/16/2020 - photo Darwin Yánez, técnico SNGRE / via IGEPN

El Reventador - 07.22.2020 / 02:46 UTC - IR image of the pyroclastic flow - Doc. IGEPN

El Reventador - 07.22.2020 / 02:46 UTC - IR image of the pyroclastic flow - Doc. IGEPN

The activity of the El Reventador volcano is currently HIGH with an ASCENDING trend; However, it is important to note that this variation does not exceed the levels observed in the volcano in recent months and years.

The most likely scenario is a continuation of the eruptive activity, with fluctuations. The main scenario proposed involves the recurrent generation of pyroclastic flows (CDP) whose deposits accumulate on the flanks of the volcano.

In this scenario, the main phenomena likely to affect the population are:

- ash falls associated with explosive activity and the remobilization of material lifted by currents of pyroclastic density. This ash, thus generated, is governed by the direction and speed of the wind, which at this time of year is typically strong and directed towards the west. Based on the data available to date, this scenario is most likely in the short term.

- Another phenomenon, less recurrent but probable, is constituted by mudslides (lahars) in rivers (whose sources originate in the volcano), this associated with the occurrence of heavy rains, typical of this region and capable of transporting the material accumulated on the flanks of the volcano.

 

Source: IGEPN

Kilauea - Halama'uma'u- crater lake level and surface variations on August 2, 2019, shows a small green pond about 2m deep, left image. The image on the right, taken on July 21, 2020, shows a lake over 40m deep with bronze to brown undertones and a sharp color border often intersecting the lake. - photo USGS / HVO - one click to enlarge

Kilauea - Halama'uma'u- crater lake level and surface variations on August 2, 2019, shows a small green pond about 2m deep, left image. The image on the right, taken on July 21, 2020, shows a lake over 40m deep with bronze to brown undertones and a sharp color border often intersecting the lake. - photo USGS / HVO - one click to enlarge

Kilauea, one year later:

Over the past year, the Kilauea summit water lake has grown to over 270m long and 131m wide, with an area of ​​over 2.5 hectares. The lake is over 40m deep and has a volume of about 480,000 cubic meters, the equivalent of nearly 200 Olympic swimming pools.

 

Source: HVO - USGS

In the Reykjanes Peninsula, since the start of the intense seismic swarm at Fagradalsfjall on July 18, activity has slowly declined over time. The acquisition of recent satellite images made it possible to map new surface deformations in the area associated with the sequence of large earthquakes that occurred between July 18 and July 20.

Reykjanes Peninsula - InSAR image / Sentinel data, July 16-22, 2020 - Doc. IMO

Reykjanes Peninsula - InSAR image / Sentinel data, July 16-22, 2020 - Doc. IMO

Volcanic systems of the Reykjanes Peninsula
Volcanic systems of the Reykjanes Peninsula

Volcanic systems of the Reykjanes Peninsula

The processing of satellite data clearly shows a deformation signal corresponding to about 3 centimeters of movement along a fault oriented NE-SW in the region of Fagradalsfjall (see black box in the figure above). This fault was identified during the 2017 earthquake swarm that also occurred in this area. Current seismic activity is interpreted as part of a larger-scale volcano-tectonic reactivation event in the Reykjanes Peninsula.

Satellite images also reveal a localized subsidence signal in the Svartsengi region (see photo above - red box). The observed subsidence began between July 16 and 18 (shortly before the major tectonic earthquakes occurred at Fagradalsfjall) and the next satellite image (scheduled for the end of this week) will confirm whether deflation is still in progress or if it has stopped. A modeling of the deformation will be undertaken to verify the origin of this signal.

No significant changes are reported regarding the geochemical measurements carried out this week on the peninsula. In addition, the Svartsengi geothermal power plant reports no changes in its routine measurements.

Ongoing activity on the Reykjanes Peninsula, which began in late 2019, reflects a widespread volcano-tectonic reactivation of much of the peninsula, which currently stretches from Eldey in the west to to Krýsuvík to the east. Activity (including additional earthquakes and magmatic intrusions) is likely to continue, with the focus shifting between different areas along the peninsula.

 

Possible dangers:

- Landslides and rock falls can be triggered by earthquakes, most likely in areas with unstable slopes, steep cliffs and loose material

- Earthquakes of up to M5.5-6 could occur in areas along the Reykjanes Peninsula with the potential to affect the captial region

- A build-up of gas in depressions can occur in very calm winds.

 

Source: IMO

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