Colombia lowers alert level for Nevado del Ruiz volcano

After 89 days of Orange alert due to increased seismic activity, Colombia’s geological service lowered the Nevado del Ruiz volcano’s alert level to Yellow on June 27, 2023. The de-escalation follows a period of decreased instability, paving the way for the potential easing of preventative measures.

Following three months of increased activity, Colombia’s geological service lowered the Alert Level for the Nevado del Ruiz volcano. The decision took place on June 27, 2023, signaling a period of decreased instability after a tense period of seismic activity.

The Nevado del Ruiz, a stratovolcano straddling Colombia’s Tolima and Caldas provinces, holds a tragic history as the cause of the country’s largest natural disaster in 1985 when an eruption led to devastating avalanches of earth and rock fragments, burying entire settlements and causing over 25 000 fatalities.

An intense eruption at 14:02 UTC on March 20, 2023, was followed by a notable increase in daily seismic activity from March 24 onwards. In one day, more than 9 400 seismic events were registered, escalating to above 11 000 on March 25 – the highest recorded number since the 1985 eruption.

The remainder of March saw an unprecedented daily average of 9 000 earthquakes. This phenomenon coincided with persistent thermal anomalies in the volcano’s crater since October 2022, detectable through satellite imagery. These anomalies suggested a possible intrusion of magma from the south, at depths of about 3 km (1.8 miles).

April 2 recorded 5 400 seismic events, with five reaching a magnitude of 2.0 and one of 2.3. By April 3, the maximum height of the gas and/or ash column measured from the volcano’s peak was 1 200 m (4 000 feet).

Faced with a possible eruption larger than any in the past decade, the Geological Service raised the Alert Level to Orange and initiated preventative evacuations near the volcano’s summit. This decision also led to the closure of the National Natural Park Los Nevados and an announcement that all schools within a 10 km (6 miles) radius of the volcano’s crater would conduct online classes post-Easter holidays.

An estimated 30 communities along a volcanic belt extending through Tolima, Caldas, and Antioquia departments, including towns in the Magdalena River basin, could have been impacted by a potential eruption. With the lowered activity level, a sense of relative calm might return, yet the memories of the 1985 tragedy still underscore the need for constant vigilance.

Featured image credit: SGC