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Copahue

The Sulfur Cauldron of the Southern Andes

Elevation

2,953 m

Last Eruption

2024

Type

Stratovolcano

Country

Chile-Argentina

Location

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Volcanic Hazards & Risk Assessment

Primary Hazards

  • Pyroclastic flows
  • Lava flows
  • Volcanic bombs and ballistics
  • Lahars and mudflows

Risk Level

Population at RiskLow
Infrastructure RiskHigh
Aviation RiskSignificant

Geological Composition & Structure

Rock Types

Primary
Unknown
Silica Content
Varied composition

Tectonic Setting

Unknown
Intraplate setting with hotspot or regional volcanic activity.

Age & Formation

Epoch
Unknown
Evidence
Unknown

Eruption Statistics & Analysis

MetricValueGlobal RankingSignificance
Total Recorded EruptionsUnknownLowModerately active volcano
Maximum VEIVEI UnknownMinorLocal impact potential
Recent Activity2 years agoVery RecentCurrently active

Monitoring & Alert Status

Monitoring Networks

Global Volcanism Program
International eruption database

Current Status

Active
Recent volcanic activity detected. Continuous monitoring in place.

Authority Sources

Smithsonian GVP
Official volcano database

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All Chile-Argentina Volcanoes
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a view of a mountain range through the trees

Rodolfo Eduardo Ayué

via Unsplash

a view of a mountain with a cloud in the sky

Rodolfo Eduardo Ayué

via Unsplash

a pine tree with a cloud in the sky

Rodolfo Eduardo Ayué

via Unsplash

a cloud is in the sky above a house

Rodolfo Eduardo Ayué

via Unsplash

a group of pine trees with a mountain in the background

Rodolfo Eduardo Ayué

via Unsplash

a very colorful cloud in the sky over some houses

Rodolfo Eduardo Ayué

via Unsplash

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Interesting Facts

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Copahue has erupted 22 times in its recorded history, with 10 events in the 21st century alone — making it one of the most frequently active volcanoes in the Southern Andes.

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The El Agrio crater lake is among the most acidic crater lakes on Earth, with pH values below 1 in some measurements.

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Eruptions at Copahue eject chilled fragments of liquid sulfur — a rare phenomenon associated with hyper-acidic crater lake volcanism.

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The volcano straddles the Chile-Argentina border, with the summit and crater on the Chilean side and the principal at-risk communities on the Argentine side.

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A ski resort operates on Copahue's lower eastern slopes — one of the few active volcanoes in the world with a ski area on its flanks.

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The name Copahue means 'place of sulfur' in the Mapuche language, reflecting centuries of indigenous awareness of the volcano's sulfuric emissions.

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The volcano is built within a nested caldera system: the 6.5 x 8.5 km Trapa-Trapa caldera inside the 20 x 15 km Caviahue caldera.

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The Rio Agrio ('Sour River'), draining from the crater lake, is one of the most naturally acidified river systems in South America.

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Nine craters are aligned along a 2-km ENE-WSW line across the summit ridge, reflecting regional tectonic stress orientation.

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The Copahue hot springs have been used therapeutically for centuries and support a modern balneotherapy resort industry.

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Chile raised the alert to Red (highest level) in December 2012, triggering evacuation of the Caviahue community (~7 km from the summit).

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All historical eruptions have been VEI 0-2 — frequent but relatively mild, dominated by phreatic explosions through the crater lake.

Frequently Asked Questions

Is Copahue volcano active?
Yes, Copahue is one of the most actively erupting volcanoes in the Southern Andes. It has produced 22 recorded eruptions, with 10 occurring in the 21st century alone. The most recent eruption was in October 2024. The volcano maintains near-persistent low-level unrest, with frequent phreatic explosions through its acidic crater lake, El Agrio. It is jointly monitored by Chile's SERNAGEOMIN and Argentina's geological survey.
Where is Copahue volcano?
Copahue straddles the border between Chile and Argentina in the southern Andes, at approximately 37.86 S, 71.18 W. The summit and crater are on the Chilean side, while the principal nearby community — Caviahue (population ~600) — lies approximately 7 km northeast on the Argentine side within the Caviahue caldera. The nearest major city is Neuquen, Argentina, approximately 350 km southeast.
What is the crater lake at Copahue?
El Agrio is a briny, highly acidic crater lake approximately 300 m wide within Copahue's eastern summit crater. It is one of the most acidic crater lakes on Earth, with pH values below 1 in some measurements. The lake is heated by volcanic gases rising from the underlying magmatic system, and its chemistry is continuously monitored as an indicator of volcanic unrest. The lake drains eastward into the Rio Agrio, creating one of the most naturally acidified river systems in South America.
Is Caviahue safe from volcanic eruptions?
Caviahue, located approximately 7 km northeast of Copahue's summit, is within the volcano's hazard zone and has been evacuated multiple times during volcanic crises — most notably in December 2012 when Chile raised the alert to Red. The primary hazards include lahars from explosive ejection of the crater lake, ashfall, and ballistic projectiles during larger eruptions. Evacuation protocols are maintained by Argentine authorities, and monitoring systems provide early warning.
Can you ski on Copahue?
Yes, the Caviahue ski resort operates on Copahue's lower eastern slopes during the Southern Hemisphere winter (approximately June-October). It is one of the few ski areas in the world located on an active volcano. However, the ski season and resort access can be affected by volcanic activity — eruptions have prompted temporary closures, and visitors should check alert levels before planning trips.
How often does Copahue erupt?
Copahue is one of the most frequently erupting volcanoes in the Southern Andes. Since its current active phase began in 1992, it has averaged roughly one eruptive episode every 1-2 years, with 10 eruptions in the 21st century alone. However, all historical eruptions have been relatively mild (VEI 0-2), dominated by phreatic explosions through the crater lake rather than large magmatic events.