The Restlessness of Cotopaxi: A “Benevolent” Eruption

An ash plume rises during the period of restlessness (Source: Talitha Engelen/Flickr).

On August 14, 2015, Ecuador’s glacier-capped Cotopaxi erupted for the first time since the 1940s. A billowing plume of ash rose early in the morning and grew through the day, reaching heights of over three miles. Two small eruptions rained ash on the southern outskirts of Quito, Ecuador’s capital 45 kilometers from the volcano. These dramatic events rattled the country and punctuated a period of seismic and low-level volcanic activity that lasted from April to November 2015.

Recently, scientists at Ecuador’s Instituto Geofísico Escuela Politécnica Nacional (IGEPN) analyzed both the physical properties of the episode and the institutional and community responses of this “dry run,” yielding information that will help Ecuador prepare for future events. Lead author and IGEPN geologist Patricia Mothes told GlacierHub that among the most important lessons learned from the period of restlessness were that “changes can occur very rapidly,” and that certain seismic trends and deformation of the volcanic cone will act as precursors to actual eruption.

The report found that over the seven months of earthquakes, degassing, ground deformation, glacial melting and plumes towering over the landscape, the activity level of the episode actually remained relatively low, at two out of eight on the Volcanic Explosivity Index.

An IGEPN report figure showing the relationship between Cotopaxi and major cities (Source: IGEPN).

Nevertheless, the impacts of the activity were manifold. Heat from the rising magma, in tandem with the layer of dark ash that formed on the glaciers, increased melting and formed new crevasses. People donned masks to avoid breathing in the ash, which damaged crops, sickened livestock, and lowered visibility on the roads for people in transit across the country. Some residents hastily sold their land and livestock or abandoned them entirely. The net effect was to depress the local economy.

With this geophysical unrest came unrest to those living near the volcano. The controversial President Rafael Correa declared a state of emergency, and thousands of residents of nearby villages evacuated to safer areas. After weeks to months of displacement in shelters and other towns, some returned to their homes, but recovery was slow and incomplete. In addition to economic harm, the volcanic activity had psychological dimensions. The Atlantic reported that people living in the risk zone experienced sleeplessness, anxiety, depression, and Post Traumatic Stress Disorder.

The most intense threat to Ecuadorians was the potential of lahars, slurries of mud and melted snow and ice that can flow for tens of miles and devastate landscapes. The geologic record shows that in each major eruption, most recently in 1877, Cotopaxi has spawned major lahars on each of its flanks. During the 2015 event, glacial melt formed small lahars that sometimes covered the road to the volcano.

A thermal image from September 3, 2015, looking toward the southeast portion of the cone (Source: IGEPN).

In the event of a more major eruption, glacial outburst floods could occur, according to Mothes. “If impacted by hot pyroclastic flows that would come out of the summit crater and careen down the steep flanks, the glaciers would be greatly eroded, ripped up, and much internal glacier water would likely be released,” she told GlacierHub. During the eruption of 1877, between five and ten meters of ice melted, and giant lahars formed. In the event of an eruption in the future, “the only mitigation scheme is to have people go to higher ground, out of the areas to be potentially affected by lahars,” said Mothes.

Communication surrounding the eruption events at the science-society interface was fraught, according to the IGEPN report. Though the agency released three updates daily, misinformation spread broadly through social media, causing panic. In response, emergency services and the IGEPN formed a “vigía (“look-out” in Spanish) network of observers near the volcano, who disseminated observations of Cotopaxi on local radio stations.

Though the 2015 period of restlessness was traumatic to those that lived through it, the authors note that the landscape and local residents have recovered from Cotopaxi’s eruptions several times throughout history. Reports from as far back as the 16th century indicate that Cotopaxi typically “warms up” slowly before erupting. At present, the IGEPN has over seventy-five scientific instruments on the volcano, continuing monitoring that began in 1986. “At the moment, there is nothing to suspect,” said Mothes.

Cotopaxi on a peaceful day (Source: Gerard Prins/Wikimedia).

The report concluded, “Overall, the volcano’s manifestations served as a warning to everyone to keep attentive of Cotopaxi’s capacity to cause destruction and possible severe ruin.” With a major eruption likely to be forthcoming, the authors called such a warning “benevolent.” Ecuador will continue to await the eventual eruption.

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