Galeras
Active stratovolcano near Pasto, Colombia; most active in the country.
Galeras, known as Urcunina to the indigenous people of the 16th century, is an active stratovolcano in Colombia’s Nariño department, close to the city of Pasto. Its peak reaches 4,276 meters (14,029 feet) above sea level. Since the Spanish conquest, it has erupted often, with the first recorded historical eruption occurring in 1535. Today, it ranks as Colombia’s most active volcano.
Geologically, Galeras has been erupting for at least a million years, producing mostly andesite. Two major caldera-forming events have shaped it: the first, around 560,000 years ago, expelled roughly 15 cubic kilometers (3.6 cubic miles) of material; the second, between 40,000 and 150,000 years ago, released about 2 cubic kilometers (0.48 cubic miles). Later, part of the caldera wall collapsed—likely due to hydrothermal instability—and subsequent eruptions built a smaller cone inside the resulting horseshoe-shaped caldera. Because of its violent history and its proximity to Pasto’s 450,000 residents, Galeras was named a Decade Volcano in 1991, making it a focus of study under the United Nations’ International Decade for Natural Disaster Reduction.
The volcano’s Holocene activity dates back to around 7050 BC (±1000 years) based on radiocarbon dating. Similar eruptions followed in 3150 BC (±200 years), 2580 BC (±500 years), 1160 BC (±300 years), 490 BC (±100 years), and 890 AD (±200 years). These events typically involved central vent explosions that generated pyroclastic flows or lahars. Recorded historical eruptions include those in 1535, December 1580, July 1616, 1641, 1670, 1754, November 1796, June 1823, October 1828, 1834, October 1865, July 1889, 1891, December 1923, October 1924, October 1932, February 1936, July 1947, January 1950, 1974, February 1989, January 1990, January 1993, March 2000, June 2002, July 2004, November 2005, October 2007, January 2008, February 2009, March 2009, January 2010, and August 2010. Unconfirmed reports also mention activity in 1836, 1930, 1933, and 1973.
After a decade of quiet, Galeras reawakened in 1988. A 1993 Decade Volcano conference in Pasto turned tragic when scientists made an impromptu trip to the crater on January 14. An unexpected eruption killed nine people total: six scientists and three tourists. Media controversy arose over suggestions that expedition leader Stanley Williams—who survived with four others—had ignored safety pr
- First historical eruption
- 1535
Quick Facts
- Elevation M
- 4276
- Prominence M
- 1,116
- Location
- Nariño, Colombia
- Range
- Central Ranges / Andes
- Volcanic Zone
- North Volcanic Zone
- Last Eruption
- 2012 to 2014
Facts from the source article.
Lore & Background
Galeras has been an active volcano for at least a million years, with andesite as the dominant product. Two major caldera-forming eruptions have occurred: the first about 560,000 years ago expelled about 15 cubic kilometres of material; the second, between 40,000 and 150,000 years ago, expelled 2 cubic kilometres. Subsequently, part of the caldera wall collapsed, possibly due to hydrothermal instability, and later eruptions built a smaller cone inside the horseshoe-shaped caldera. Its earliest Holocene activity has been dated to 7050 BC ± 1000 years through radiocarbon dating.
A 1993 eruption killed nine people total: six scientists and three tourists. The scientists had descended into the volcano's crater to sample gases and take gravity measurements in an attempt to predict an eruption, which had been anticipated based on long-period (LP) seismic events rather than B-Type activity alone.
Reader's Guide
Galeras is significant as the most active volcano in Colombia and a Decade Volcano designated in 1991 under the United Nations' International Decade for Natural Disaster Reduction, due to its violent eruptive history and proximity to the 450,000 people of Pasto. Its study has improved eruption prediction, notably through the identification of low-frequency seismic events called tornillo events, which have occurred before about four-fifths of its explosions. The 1993 eruption remains a key case in volcanology, highlighting the risks of crater expeditions and the limitations of seismic prediction. The volcano continues to be monitored by the Deep Earth Carbon Degassing Project, and its frequent eruptions—such as those in 2005, 2008, 2009, and 2010—have forced repeated evacuations and ashfall on Pasto, underscoring the ongoing hazard to the region.
Did You Know?
- Galeras was known as Urcunina among 16th-century indigenous people.
- Its first historical eruption was recorded on December 7, 1580.
- A 1993 eruption killed nine people, including six scientists who had descended into the crater.
- Tornillo seismic events have occurred before about four-fifths of the explosions at Galeras.
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