Galeras: A Deep Dive into Colombia's Restless Decade Volcano
Galeras, in southwestern Colombia, is one of the most active volcanoes in the country and looms directly over the city of Pasto and its surrounding population. Its long history of frequent eruptions led to its designation as a Decade Volcano, one of a select group identified for intensive study because of the danger they pose to large populations. Galeras is also remembered for a tragic eruption in 1993 that killed scientists working inside its crater.
A volcano above a city
Galeras reaches about 4,276 metres and rises immediately beside Pasto, a city of several hundred thousand people in the Colombian Andes. This close proximity of a frequently active volcano and a substantial urban population makes Galeras one of the highest-risk volcanoes in Colombia, and the reason it has received such intense scientific and emergency-planning attention.
A Decade Volcano
In recognition of its hazard, Galeras was designated one of the world's Decade Volcanoes, a group selected by international scientists for focused study during a United Nations initiative on natural disaster reduction. These volcanoes were chosen because they are both highly active and dangerously close to large populations, making them priorities for research and monitoring.
The tragedy of 1993
In January 1993, a group of scientists was conducting fieldwork inside the crater of Galeras during a volcanology conference held in Pasto. The volcano erupted suddenly and without clear warning, killing several of the researchers and others present. The disaster was a profound shock to the volcanological community and prompted deep reflection on the dangers of crater fieldwork and the limits of eruption prediction.
Lessons for volcanology
The 1993 eruption, like the earlier loss of scientists at Mount Unzen, reshaped how volcanologists approach risk during fieldwork. It highlighted the unpredictability of explosive eruptions and the dangers faced by those who study active volcanoes up close. The event spurred efforts to improve the recognition of precursors and to develop safer protocols for working near active craters.
Frequent ongoing activity
Galeras has remained frequently active since 1993, producing explosions, ash emissions, and dome growth, and prompting periodic evacuations of communities on its flanks. Its persistent activity keeps the city of Pasto and the surrounding region in a continuing state of preparedness, with hazard maps and evacuation plans central to managing the risk.
Living beside Galeras
The people of Pasto and the villages on Galeras's slopes live in close, ongoing relationship with the volcano. Its fertile soils support agriculture, while its eruptions periodically force evacuations and disrupt daily life. Balancing the benefits of the land with the dangers of the volcano is a constant challenge, managed through monitoring, planning, and public awareness.
Monitoring a high-risk volcano
Colombia's geological service maintains intensive monitoring of Galeras, using seismic networks, gas measurements, and ground deformation sensors to track its behaviour and issue alerts. Given its status as a Decade Volcano and its proximity to Pasto, Galeras remains one of the most closely watched volcanoes in South America, a focus of ongoing scientific and civil-protection effort.
Explore on the map
Galeras stands among Colombia's chain of active volcanoes, alongside Nevado del Ruiz and others in the Andes. Explore it on the interactive map — filter by country to see Galeras among Colombia's volcanoes and to appreciate the close coexistence of a city and a restless Decade Volcano.