🌋VolcanoAtlas

Karthala

Africa's Most Active Shield Volcano

Elevation

2,350 m

Last Eruption

2007

Type

Shield volcano

Country

Union of the Comoros

Location

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Volcanic Hazards & Risk Assessment

Primary Hazards

  • Lava flows and fountaining
  • Volcanic gas emissions
  • Local explosive activity

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 Activity19 years agoRecentRecently active

Monitoring & Alert Status

Monitoring Networks

Global Volcanism Program
International eruption database

Current Status

Watch
Dormant but monitored. Capable of renewed activity.

Authority Sources

Smithsonian GVP
Official volcano database

Related Volcanoes

All Union of the Comoros Volcanoes
Explore by country
Shield volcano Volcanoes
By volcano type
Indian Ocean
Regional volcanoes

Interesting Facts

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Karthala has erupted 35 times since approximately 1050 CE, making it one of Africa's most active volcanoes.

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The volcano forms the southern two-thirds of Grand Comore Island, making it one of the largest volcanic edifices in the Indian Ocean by land area.

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Grand Comore has no rivers or reservoirs — the island's 400,000 residents rely entirely on rainwater cisterns and shallow wells that are highly vulnerable to volcanic ashfall contamination.

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In 2005, two eruptions within seven months displaced over 40,000 people and created a humanitarian water crisis requiring international aid.

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An 1860 lava flow from the summit caldera traveled approximately 13 km to the northwest, reaching the coast just north of the capital city of Moroni.

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Between 1848 and 1883, Karthala erupted at least 14 times — an average of roughly one eruption every 2.5 years.

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Karthala's two overlapping summit calderas measure 3–4 km across and were formed by repeated roof collapses when magma drained through lateral rift zones.

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The Comoros archipelago is known as the 'Perfume Islands' because the volcanic soil supports prolific growth of ylang-ylang, vanilla, and cloves.

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The submarine eruption of Fani Maoré off Mayotte in 2018–2021 was the largest underwater eruption ever documented, occurring in the same volcanic province as Karthala.

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Karthala's basaltic lavas are so fluid that historical flows have extended to both coasts of Grand Comore, building new land where they entered the Indian Ocean.

Frequently Asked Questions

Is Karthala an active volcano?
Yes, Karthala is classified as an active volcano. It has erupted 35 times since approximately 1050 CE, with the most recent eruption occurring in January 2007. The volcano is one of the most active in the African-Indian Ocean region, having produced four eruptions between 2005 and 2007 alone. Karthala is continuously monitored by the Karthala Volcano Observatory, and volcanologists consider a future eruption likely given its historical eruption frequency of roughly one event every five to ten years.
When did Karthala last erupt?
Karthala last erupted on January 12, 2007, when activity at the Chahalé crater within the summit caldera produced explosive eruptions and briefly formed a small lava lake. This VEI 2 event was the fourth eruption in less than three years, following two damaging eruptions in 2005 (April and November) and a minor event in May 2006. The volcano has been quiet since 2007, though fumarolic activity continues at the summit.
How tall is Karthala?
Karthala stands 2,350 m (7,710 ft) above sea level, making it the tallest point in the Comoros archipelago and one of the highest volcanoes in the western Indian Ocean. The shield volcano rises from the seafloor, so its total height from base to summit is considerably greater — estimated at over 4,000 m. By comparison, Piton de la Fournaise on Réunion stands at 2,632 m, while Mount Kilimanjaro in Tanzania, Africa's tallest peak, reaches 5,895 m.
What type of volcano is Karthala?
Karthala is a shield volcano, characterized by broad, gently sloping flanks built up by successive flows of fluid basaltic lava. Shield volcanoes are typically associated with effusive eruptions rather than explosive ones. However, Karthala is unusual among shield volcanoes because its summit caldera system, which periodically fills with water, generates phreatomagmatic explosions when rising magma encounters groundwater — producing ash plumes and explosive activity more commonly associated with stratovolcanoes.
Why is Karthala dangerous?
Karthala poses an unusually concentrated risk because approximately 400,000 people live on Grand Comore Island with virtually no alternative water sources. The island has no rivers, lakes, or reservoirs — residents depend on rainwater cisterns and shallow wells. Even a moderate eruption from the summit caldera can contaminate these water sources with volcanic ash and acid, creating an immediate humanitarian crisis, as occurred twice in 2005. Additionally, lava flows from flank eruptions can reach the coast within hours, threatening villages and infrastructure including the capital city of Moroni.
Can you hike Karthala?
Yes, Karthala can be climbed, typically starting from the village of M'vouni on the western flank. The ascent takes 6–8 hours through tropical forest, montane scrub, and barren volcanic terrain, with the descent requiring 4–5 hours. Local guides are strongly recommended as the trail is not well-marked. The summit caldera offers dramatic views of active fumaroles and the crater floor. There are no mountain huts, so trekkers must carry all supplies. Climbers should check volcanic activity status beforehand, as access may be restricted during unrest periods.
Where is Karthala located?
Karthala is located on Grand Comore Island (also called Ngazidja), the largest and westernmost island in the Comoros archipelago, in the Mozambique Channel of the western Indian Ocean. The volcano lies approximately 300 km northwest of Madagascar and 300 km east of the Mozambique coast of East Africa. The summit coordinates are 11.766°S, 43.364°E. The Comorian capital, Moroni, sits on the island's western coast approximately 12 km from the summit.
How often does Karthala erupt?
Karthala erupts frequently by global standards. Over the past two centuries, it has averaged roughly one eruption every six to eight years, though activity is highly clustered — the 19th century saw 21 eruptions (about one every five years), while the period from 1928 to 1948 was comparatively quiet. The most recent cluster of four eruptions occurred between April 2005 and January 2007. The current repose period since 2007 is approaching two decades, which is among the volcano's longer quiet intervals in the historical record.