Cerro Negro de Mayasquer volcanic complex located at the Ecuador-Colombia border is experiencing increased volcanic unrest and inflation. Authorities raised the alert level to Orange (3/4) and ordered thousands to evacuate amid fears that the recent activity under the volcano might result in an eruption.
A special bulletin by Ecuadorian IGEPN states that the recorded deformation has increased in recent days and that the observed monitoring parameters are compatible with the scenario of a magma intrusion that could lead to a sudden, potentially large, phreatic or even magmatic eruption, even on a short timescale (weeks).
On October 20, 2014 Servicio Geológico Colombiano (SGC) reported that a M5.8 earthquake (19:21 UTC), the largest to date, occurred in the vicinity of the Cerro Negro de Mayasquer and Chiles volcanoes at a depth of less than 10 km. The event was felt to the N in Pasto (Colombia) and to the S in Quito (Ecuador). On October 21 SGC raised the Alert Level for the volcanic complex to Orange (level 3 of 4) noting that a seismic swarm characterized by 4 300 earthquakes was detected in an 18-hour period.
Hypocenters were located 1 - 4 km SW of Chiles volcano at depths of 3 - 5 km and local magnitudes between M0.2 and 4.5. Inhabitants felt 11 of the events. On October 22 a report noted that the total number of earthquakes recorded on October 21 reached 7 717, which was the largest number of earthquakes recorded on one day since the installation of a local seismic network in 2013.
The recent crisis could be the sign of magma rising with the volcano and result in an eruption, although it is not possible to quantify how likely this might be, VolcanoDiscovery said.
The volcano has had two impressive peaks of earthquakes since the network was installed. The first one occurred between September 2013 and January 2014 with over 100 000 small events detected. A second peak with 25 000 quakes occurred between late April and July this year, when the alert level was first raised to yellow.
A new seismic swarm has started on September 29 and until now counts nearly 40 000 quakes.
On Thursday, October 23 Colombia ordered the evacuation of more than 3 500 families (around 12 000 people) living near the volcano. "In accord with the forecast given to us by the Geological Service, the change of alert level from Yellow to Orange means anticipated eruptions in the coming days or weeks," the director of the Colombian disaster risk management unit said.
There is no known eruption of Cerro Negro de Mayasquer volcanic complex in the past 10 000 years.
Cerro Negro de Mayasquer, astride the Colombia-Ecuador border, is a stratovolcano with a caldera open to the west. Andesitic and dacitic lava flows are of possible Holocene age (Hall 1992, pers. comm.). Solfataras are found on the shore of a small crater lake.
An historical eruption reported in 1936 may have been from Reventador (Catalog of Active Volcanoes of the World). The higher, glacier-covered summit of the Pleistocene Chiles stratovolcano lies only 3 km SE. Chiles last erupted about 160,000 years ago, but has hot springs and an active hydrothermal system at its eastern flank. (GVP)
Featured image: Cerro Negro de Mayasquer. Credit: GVP