Karthala Volcano | John Seach


Grand Comore Island, Comoros

11.75 S, 43.38 E
summit elevation 2361 m
shield volcano

Karthala volcano is located on Grande Comore, the most westerly of four volcanic islands comprising the Comores Archipelago, between northern Madagascar and Mozambique. Karthala occupies the southern half of Grand Comore Island.

The islands of the Comores archipelago become progressively younger westwards towards Karthala volcano.

The caldera, is elliptical in shape, 4 km long and 3 km wide, with outer walls around 100 m high. It is dominated by a large central pit crater, Chahale, which is 1300 m long, 800 m wide, and 300 m deep. A smaller cylindrical pit crater 250 m in diameter and 30 m deep, Changomeni, is found one km north of Chahale.

Historic eruptions Karthala volcano are distributed along a rift zone 6-8 km wide, extending NNW-SSE across the island for 45 km. Since 1918, eruptions have occurred near the summit of Karthala, or very close to the caldera. Karthala eruptive styles are mostly effusive, but phreatic explosions occurred in 1918, 1948, 1952, 1991, and 2005.

2012 Activity
Incandescence was observed at the summit of Karthala volcano on 9-10 May 2012.

2007 Eruptions
An eruption occurred at Karthala volcano on 12th January 2007. A lava lake was confined to the crater on 15th January. Earthquakes over magnitude 4 were felt by resident on the island, forcing some people to evacuate.

2006 Eruptions
On 28th May 2006, a magmatic eruption occurred inside the Chahalé caldera of Karthala volcano. From the coast a red cloud was visible above the volcano. The eruption was contained inside the main (Chahalé) crater, where the past three eruptions had occurred. The surface of the lava lake solidified by 2nd June 2006.

2005 Eruptions
Two large eruptions occurred at Karthala Volcano in 2005, affecting 40,000 people in April and 175,000 people in November.

1991 Eruption
A phreatic eruption occurred at Karthala volcano in July 1991. An active hydrothermal system is believed to exist beneath Karthala volcano. There is a surface manifestation of geothermal activity at a solfatara, La Soufriere, located in the upper part of the north rift zone, and water level changes of the 1991 Karthala crater lake, not correlated with rainfall, suggest the existence of an active hydrothermal system. The hydrothermal system was not in equilibrium 4 years after the 1991 explosion, as indicated by ongoing seismicity.

1972 Eruption
A Strombolian eruption began on the afternoon of 8th September 1972 and continued until 5th October. Lava was emitted from four fissures within the caldera and possibly an external fissure. The eruption was vigorous on 8-9 September, decreased for a few days, and reached a maximum intensity during 13-15 September. During the initial two days a flow of aa lava was emitted along 600 m of an old fissure zone. The 1972 lavas consist of rough, scoriaceous and a slabby-surfaced aa. The flows covered an area of approximately 2.5 sq km.

1965 Eruption
On 12th July 1965, a small basaltic aa lava flow emitted from a short NNE-SSW fissure linking Choungou Chahale and Choungou Chagnoumeni and a portion of this flow descended into the Chahale pit crater.

1952 Eruption
In February 1952, a small Strombolian-type eruption occurred in the Chagnoumeni pit.

1948 Eruption
In April 1948 a Strombolian-type eruption was reported from Choungou Chagnoumeni collapse pit in which blocks were hurled over one hundred metres high.

1918 Eruption
The eruption of 1918 began suddenly in the night of August 11-12, with intense light flashes signalling the opening of a crevasse on the north flank of Karthala at an altitude of 1980 meters, about 600 meters above the source of the 1904 eruption. Seismic activity was felt on the flanks of the volcano until 23rd August, when a violent earthquake was felt on all of Grande Comore and the neighbouring island of Moheli. Violent explosive activity occurred within the caldera.

Further reading
Strong, D.F. and Jacquot, C., 1970. The Karthala Caldera, Grande Comore. Bulletin Volcanologique34(3), pp.663-680.

Bachelery, P., Lenat, J.F., Di Muro, A. and Michon, L. eds., 2015. Active Volcanoes of the Southwest Indian Ocean: Piton de la Fournaise and Karthala. Springer.

Karthala Volcano Eruptions

2007, 2006, 2005, 1991, 1977, 1972, 1965, 1956, 1952, 1948, 1928, 1918, 1910, 1904, 1883-84, 1880, 1876, 1872, 1865, 1862?, 1860, 1859, 1858, 1857, 1855, 1850?, 1848, 1833, 1830, 1828, 1821, 1814, 1808, 1050.