The Nevado del Ruiz volcano is situated northwest of Colombia’s capital, Bogotá. Part of the Cordillera Central of the Colombian Andes, the volcano is one of several that lie within Los Nevados National Natural Park. Its 1985 eruption was the fourth-deadliest in recorded history.
Nevado del Ruiz Volcano
The Nevado del Ruiz volcano is situated approximately 140 km (87 mi) northwest of Colombia’s capital, Bogotá. Part of the Cordillera Central of the Colombian Andes, the volcano is one of several that lie within Los Nevados National Natural Park.
The massif is located at the intersection of four faults, some of which are still active. The volcano is fed by magma generated above the boundary between the subducting Nazca plate and the overriding South American plate.
Nevado del Ruiz lies within the Pacific Ring of Fire, a region that encircles the Pacific Ocean and contains some of the world's most active volcanoes. It is the third most northerly of the volcanoes lying in the North Volcanic Zone of the Andean Volcanic Belt.
Covering over 200 sq km (77 sq mi), Nevado del Ruiz is a large stratovolcano: a cone-shaped volcano built from successive layers of lava, ash and pyroclastic-flow deposits. The modern volcanic cone comprises five lava domes, all constructed within the caldera of an ancestral Ruiz volcano.
The summit of the volcano has steep slopes inclining from 20 to 30 degrees. At lower elevations, the slopes become less steep. The volcano's foothills stretch toward the Magdalena River in the north and to the Cauca River in the west.
The summit of Nevado del Ruiz is covered by glaciers that formed over many thousands of years and have generally retreated since the last glacial maximum.
The meltwater from the glaciers drains primarily to the Cauca River and Magdalena River via the western and eastern flanks of the volcano, respectively. Runoff from these glaciers and those on the surrounding volcanoes are a source of fresh water for a number of surrounding towns.
Since the 1985 eruption, which destroyed about 10% of the summit ice cover, the area of Nevado del Ruiz covered by glaciers has halved. The deep ice covering the summit plateau may hide a caldera (large crater). Five domes ringing the summit plateau have emerged as the ice has retreated.
The historical record of eruptions at the volcano extends back to 1570 but the most damaging eruption in recent times took place in 1985.
On November 13, 1985, an explosive eruption at the Arenas Crater melted ice and snow at the summit of the volcano. The eruption produced pyroclastic flows that melted summit glaciers and snow, generating four thick mudflows (lahars) that swept tens of kilometers down river valleys along the volcano’s flanks, killing at least 23,000 people. Most of the fatalities occurred in the town of Armero which was completely inundated by lahars.
The Armero tragedy, as the event came to be known, was the second-deadliest volcanic disaster in the 20th century, being surpassed only by the 1902 eruption of Mount Pelée. It was the fourth-deadliest volcanic eruption in recorded history, the deadliest known lahar and Colombia's worst natural disaster.