Active Volcanoes of Colombia: Between Natural Beauty and Eruptive Risks

Journey to the Heart of Colombia's Active Volcanoes

The Andes is the longest mountain range in the world (7,100 kilometers long). It runs along the western coast of South America, passing through Venezuela, Colombia, Ecuador, Peru, Bolivia, Chile, and Argentina.

Its average altitude is 4,000 meters, and its highest peak is Aconcagua in Argentina, which stands at 6,962 meters. Many peaks are volcanoes created by the subduction of the Pacific plate under the South American plate. The main mountains of Colombia are: Pic Cristóbal Colón (5,775 m), Pic Simón Bolívar (5,775 m), Ritacuba Blanco (5,410 m), Nevado del Huila (5,365 m), Nevado del Ruiz (5,321 m), Nevado de Quindio (5,215 m), Nevado del Tolima (5,200 m), Galeras (4,276 m).

The main active volcanoes are: Cerro Machin volcano (2,750 m), Nevado del Ruiz volcano (5,320 m), Nevado del Huila volcano (5,365 m), and Galeras volcano (4,275 m).

N.B.: The word "volcano" comes from Vulcano, one of the Aeolian Islands named in honor of Vulcan, the Roman god of fire. His Greek counterpart is Hephaestus. For the Romans, Vulcan was one of the three sons of Jupiter and Juno. Vulcan ruled the fiery depths of volcanoes.

Cerro Machin Volcano

Cerro Machin: From Observation to Prevention

Cerro Machin has the lowest altitude of the volcanoes in Colombia (2,750 m). It is located 150 km southwest of Bogota, 17 km west of Ibague, and 30 km east of the city of Armenia on the eastern slope of the central cordillera. Cerro Machin is in a region with a warm temperate climate and an average temperature of 20°C.

Although it has not erupted since the year 1180, it is an active volcano with three domes in the central ring. The center of the 2.4 km diameter crater is occupied by several domes with fumarolic activity and hot springs. In the crater of this explosive volcano, there is a beautiful crescent-shaped pond.

The currently dormant Cerro Machin could awaken with a powerful explosion like in the past. The domes are actually the plugs of the volcanic vents from which tephras such as pyroclastic ash and pumice stones, pyroclastic flows, and rock blocks, as well as mudflows called lahars, emerged during ancient explosions.

Mudflows or lahars are generally devastating. They rush down the mountains and engulf everything in their path, including trees, bridges, cars, buildings, etc. The volcanic activity of the Machin volcano has increased since 1998, with more frequent small earthquakes and fumaroles. Geologists are monitoring radon gas emissions and possible deformations of the domes that obstruct the crater.

N.B.: A lahar is a volcanic mudflow. It is primarily composed of water, volcanic ash, and tephras.

Nevado del Ruiz Volcano

Nevado del Ruiz: Eruptive Mechanisms and Impact on Populations

The glacier-covered Nevado del Ruiz is one of the highest volcanoes in Colombia (5,300 meters). It is also the second most active volcano after Galeras. Its glaciers surround the Arenas crater.

Nevado del Ruiz was formed by subduction volcanism and has experienced frequent Plinian eruptions during the Holocene, i.e., over the last 10,000 years. However, it was in 1985 that one of the deadliest explosions in Colombia occurred. It almost completely devastated the town of Armero. Since then, the monitoring of this volcano has been constant because hundreds of thousands of people live in the surrounding valleys.

After 69 years of dormancy, Nevado del Ruiz erupted on September 11, 1985, until July 13, 1991. The lahar engulfed part of the town of Armero on the night of November 13-14, 1985, killing nearly 20,000 of the town's 29,000 inhabitants in their sleep. It was a catastrophic scenario because the pyroclastic flows from the crater carried the melted snow from the glaciers, and four enormous lahars rushed down the mountain's slopes at 60 km/h. The lahars flowed into the beds of the volcano's six rivers and covered the town of Armero. The world remembers the video images of 13-year-old Omayra Sánchez agonizing in a viscous mudflow.

N.B.: A Plinian eruption is a type of volcanic eruption with emissions of viscous lava that occurs on gray volcanoes. This lava plugs the volcanic vent, and the internal pressure in the volcano increases until it causes gigantic explosions that can destroy the volcano itself and give rise to a caldera.

Nevado del Huila Volcano

Nevado del Huila: A Moderate Volcanic Complex

Nevado del Huila is a moderately active volcanic complex consisting of several stratovolcanoes and domes. It is located in the department of Huila (Colombia) in the central Andes. It is the highest volcano in the Colombian Andes (between 5,364 and 5,750 meters) and is therefore covered by an ice cap.

This volcano was built within an ancient caldera ten kilometers in diameter, from which several volcanic domes emerge: Pico Norte, Pico la Cresta, Pico Central, and Pico Sur. The volcanism of Nevado del Huila has produced six volcanic cones. It is currently an enormous mountain (16 km x 11 km). The only activity is the sound of its permanent rumbling.

Galeras Volcano

Galeras: Geology and Eruptive Phenomena

The Galeras volcano is a stratovolcano in the Andes in the Colombian department of Nariño, 9 km from the capital, San Juan de Pasto. The indigenous people called it "Urcunina," meaning Mountain of Fire. Later, the Spanish conquerors named it "Galeras" for its resemblance to galleys or sailing ships.

The Galeras volcano is known as a volcanic complex. It has a conical shape, and the western part of the edifice is destroyed. Its summit rises to 4,276 meters in altitude. It erupts frequently since its historical eruption on December 7, 1580.

Galeras has been an active volcano for at least a million years, primarily spewing andesite. The ancient major eruptions built the caldera, part of whose wall is currently collapsed. Inside the caldera, there is a small horseshoe-shaped cone.

N.B.: Andesite is a gray volcanic igneous rock characteristic of the volcanism in subduction zones.