Where is Nevado del Ruiz and when was the last time it erupted?

( Spanish) — The Nevado del Ruiz volcano, which is located on the border of the departments of Caldas and Tolima, in Colombia, registered a “significant increase” in seismic activity.

On March 30, the Colombian authorities raised the risk level of the volcano to orange, since “there is a probability that in days or weeks the Nevado del Ruiz volcano will erupt more than it has in the last decade.” explained the Colombian Geological Service (SGC) and the National Unit for Disaster Risk Management (Ungrd) in a joint statement.

From the increase to orange level, the Caldas Environment Secretariat decided to close the Los Nevados National Natural Park and the evacuation of the “areas surrounding the volcano, particularly the riverside or ravine areas” began.

“Although there is the probability of an eruption of days or weeks, it does not necessarily have to happen, that means that you cannot lower your guard. The volcano is still very unstable, so it is the opportune moment for there to be greater awareness and greater preparation, so that —in the event of an eruption— we can respond in the best way,” explained Jhon Londoño Bonilla, technical director of SCG Geohazards, according to the government of Caldas.

The Nevado del Ruiz, which has had minor eruptions in the last 10 years, is known worldwide for its eruption on November 13, 1985, which affected the town of Armero. On that occasion, the volcano released rivers of volcanic material and mud that devastated everything in its path. The Government of Colombia recorded at that time that the tragedy left nearly 25,000 dead.

But when was the last time it erupted?

The Nevado del Ruiz volcano, a 5,321-meter-high mountain located west of Armero in a prosperous rural town in northern Tolima, Colombia, last erupted on September 1, 1989.

According to the QMS, the main event began at 03:06 local time and the eruption lasted 2 hours and 24 minutes. The eruption on September 1 divided into two maximum points and generated an eruptive column more than 8 kilometers high above the crater. However, this was controlled by the strong winds that arose.

In addition to the eruption, Nevado del Ruiz also generated a flow of sediment and water —known as lahar—, similar to the one that occurred in the deadly eruption of September 11, 1985, indicates the SGC. However, the 1989 eruption was considered “the first success in volcanic monitoring and therefore in volcanic risk management in Colombia” and therefore the necessary measures were taken to avoid a catastrophe.

This is the historical activity of the Nevado del Ruiz volcano, according to the Colombian Geological Service.

March 12, 1595:parasitic crater subglacial explosion with lahars and destruction of land and property.

March 14, 1805: burst.

June 1828: burst.

February 19, 1845: Subglacial radial eruption with lava flow, mudflow, destruction of property and land, and over 1,000 deaths.

December 1984: emission of sulfur gases. Reactivation.​

September 11, 1985: ash emission with sludge flow.​

November 13, 1985: magmatic phreate eruption with mudflows. Destruction of land and property. More than 25,000 dead.

Armero was buried under a mudslide on November 13, 1985 after an eruption of the Nevado del Ruiz volcano (Credit: STF/AFP/Getty Images)

January 4-6, 1986: ash emission.

July 20, 1986: ash emission.

July 29, 1986: ash emission.

July 9-11, 1987: ash emission.

March 22-25, 1988: ash emission.

September 1, 1989: freato-magmatic eruption.

March and April 1994: seismic reactivation

At the moment: A higher than unusual seismic activity has been recorded in the Nevado de Ruiz, as well as the expulsion of gases and ash. On March 30, 9,600 earthquakes were recorded inside the volcano; on April 1, 10,400 were registered; on April 3, 5,000; on April 4, 5,200; and during the first hours of April 5, more than 2,600 earthquakes.

With information from Marlon Sorto, Wilson Barco, Federico Jofre and Stefano Pozzebon, all from .