Colo

Stratovolcano in Indonesia

Last Eruption: 1983

Key Facts

Elevation

404 m (1,325 ft)

Type

Stratovolcano

Location

-0.162°, 121.601°

Region

Sangihe Volcanic Arc

Rock Type

Trachyandesite / Basaltic Trachyandesite

Tectonic Setting

Subduction zone

Location

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Overview

Colo volcano forms the isolated small island of Una Una in the middle of the Gulf of Tomini in northern Sulawesi. The broad, low volcano contains a 2-km-wide caldera with a small central cone. Three eruptions have been recorded since the late 1800's, but two of those caused widespread damage over the island.

The last eruption, in 1983, produced pyroclastic flows that swept over most of the island shortly after all residents had been evacuated.

Volcanic Hazards & Risk Assessment

Primary Hazards

Pyroclastic flows
Lava flows
Volcanic bombs and ballistics
Lahars and mudflows

Risk Level

Population at RiskModerate

Infrastructure RiskHigh

Aviation RiskSignificant

Geological Composition & Structure

Rock Types

Primary

Trachyandesite / Basaltic Trachyandesite

Silica Content

Low (45-52% SiO₂)

Tectonic Setting

Subduction zone

Formed by oceanic plate subduction, typically producing explosive eruptions due to water-rich magmas.

Age & Formation

Epoch

Holocene

Evidence

Eruption Observed

Eruption Statistics & Analysis

Metric	Value	Global Ranking	Significance
Total Recorded Eruptions	Unknown	Low	Moderately active volcano
Maximum VEI	VEI Unknown	Minor	Local impact potential
Recent Activity	43 years ago	Recent	Recently active

Monitoring & Alert Status

Monitoring Networks

Global Volcanism Program

International eruption database

Current Status

Watch

Dormant but monitored. Capable of renewed activity.

Nearby Volcanoes in Western Pacific Volcanic Regions

Regional Volcanic Activity

The Western Pacific Volcanic Regions contains multiple active volcanic systems. Cross-regional magma interactions and tectonic stresses can influence eruption patterns across the entire arc. Monitor regional seismic activity and volcanic alerts.

Quick Info

•Smithsonian ID: 266010
•Evidence: Eruption Observed
•Epoch: Holocene

About the Photo

Ash mantles the summit of Colo volcano after a powerful explosive eruption in 1983. The volcano forms the isolated island of Una-Una in the middle of the Gulf of Tomini in northern Sulawesi. The broad, low volcano is truncated by a 2-km-wide caldera that contains a small central cone. Only three eruptions have been recorded in historical time. The last eruption, in 1983, produced pyroclastic flows that swept over most of the island shortly after all residents had been evacuated.

Photo by M.S. Santoso, 1983 (Volcanological Survey of Indonesia).