The Comoros is formed by Ngazidja (Grande Comore), Mwali (Mohéli) and Nzwani (Anjouan), three major islands in the Comoros Archipelago, as well as many minor islets. The islands are officially known by their Comorian language names, though international sources still use their French names (given in parentheses above). The capital and largest city, Moroni, is located on Ngazidja. The archipelago is situated in the Indian Ocean, in the Mozambique Channel, between the African coast (nearest to Mozambique and Tanzania) and Madagascar, with no land borders.
At 2,034 km2 (785 sq mi), it is one of the smallest countries in the world. The Comoros also has claim to 320 km2 (120 sq mi) of territorial seas. The interiors of the islands vary from steep mountains to low hills.
Ngazidja is the largest of the Comoros Archipelago, approximately equal in area to the other islands combined. It is also the most recent island, and therefore has rocky soil. The island's two volcanoes, Karthala (active) and La Grille (dormant), and the lack of good harbours are distinctive characteristics of its terrain. Mwali, with its capital at Fomboni, is the smallest of the four major islands. Nzwani, whose capital is Mutsamudu, has a distinctive triangular shape caused by three mountain chains – Sima, Nioumakélé and Jimilimé – emanating from a central peak, Mount N'Tingui (1,575 m or 5,167 ft).
The islands of the Comoros Archipelago were formed by volcanic activity. Mount Karthala, an active shield volcano located on Ngazidja, is the country's highest point, at 2,361 metres (7,746 feet). It contains the Comoros' largest patch of disappearing rainforest. Karthala is currently one of the most active volcanoes in the world, with a minor eruption in May 2006, and prior eruptions as recently as April 2005 and 1991. In the 2005 eruption, which lasted from 17 to 19 April, 40,000 citizens were evacuated, and the crater lake in the volcano's 3 by 4 kilometres (1.9 by 2.5 miles) caldera was destroyed.
The Comoros also lays claim to the Îles Éparses or Îles éparses de l'océan indien (Scattered Islands in the Indian Ocean) – Glorioso Islands, comprising Grande Glorieuse, Île du Lys, Wreck Rock, South Rock, Verte Rocks (three islets) and three unnamed islets – one of France's overseas districts. The Glorioso Islands were administered by the colonial Comoros before 1975, and are therefore sometimes considered part of the Comoros Archipelago. Banc du Geyser, a former island in the Comoros Archipelago, now submerged, is geographically located in the Îles Éparses, but was annexed by Madagascar in 1976 as an unclaimed territory. The Comoros and France each still view the Banc du Geyser as part of the Glorioso Islands and, thus, part of its particular exclusive economic zone.
The climate is generally tropical and mild, and the two major seasons are distinguishable by their raininess. The temperature reaches an average of 29–30 °C (84–86 °F) in March, the hottest month in the rainy season (called kashkazi/kaskazi [meaning north monsoon], which runs from December to April), and an average low of 19 °C (66 °F) in the cool, dry season (kusi (meaning south monsoon), which proceeds from May to November). The islands are rarely subject to cyclones.
Ecology and environment
The Comoros constitute an ecoregion in their own right, Comoros forests.