La Grille is a

volcano A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates are ...

in the

Comoros archipelago The Comoro Islands or Comoros (Shikomori ''Komori''; ar, جزر القمر , ''Juzur al-qamar''; french: Les Comores) form an archipelago of volcanic islands situated off the southeastern coast of Africa, to the east of Mozambique and northwes ...

on the island of

Grande Comore Grande Comore () is an island in Comoros off the coast of Africa. It is the largest island in the Comoros nation. Most of its population is of the Comorian ethnic group. Its population is about 316,600. The island's capital is Moroni, Comoros, ...

(also known as

Ngazidja Grande Comore () is an island in Comoros off the coast of Africa. It is the largest island in the Comoros nation. Most of its population is of the Comorian ethnic group. Its population is about 316,600. The island's capital is Moroni, which is ...

Description

La Grille is a shield volcano at the northern end of island and lacks a summit caldera like its larger and more well-known neighbour to the south, Karthala volcano. The

basaltic Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% of a ...

La Grille volcano also differs from Karthala in its abundance of

pyroclastic cones Volcanic cones are among the simplest volcanic landforms. They are built by ejecta from a volcanic vent, piling up around the vent in the shape of a cone with a central crater. Volcanic cones are of different types, depending upon the nature and s ...

up to in height. The cones were erupted along

fissures A fissure is a long, narrow crack opening along the surface of Earth. The term is derived from the Latin word , which means 'cleft' or 'crack'. Fissures emerge in Earth's crust, on ice sheets and glaciers, and on volcanoes. Ground fissure A ...

running parallel to the summit ridge, which has an irregular profile and is elongated in a north-south direction, and from radial fissures that reach as far as the coast. Although the exact date of the last eruption of La Grille is unknown, lava flows covering its sides and not yet recolonized by vegetation suggest that the volcano last erupted only a few hundred years ago. Recent

lava flows Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ...

, some possibly as young as a few hundred years, have reached the sea from fissures on the lower western, northern, and eastern flanks.

Geography

La Grille is located on the island of Grande Comore, a northern island of the Comoros archipelago in the

Mozambique Channel The Mozambique Channel (french: Canal du Mozambique, mg, Lakandranon'i Mozambika, pt, Canal de Moçambique) is an arm of the Indian Ocean located between the Southeast African countries of Madagascar and Mozambique. The channel is about long ...

in the Indian Ocean. The volcano is abutted on the south by Karthala, another volcano rising to meters. A road around the coast of Grande Comore runs along the east, north and west sides of La Grille, connecting Prince Said Ibrahim Airport to the west of the island. Many villages are located near the coast and on the volcano, where there are also electricity pylons. La Grille appears as a mountain range running from north to south, reaching a slag height of meters on average, and covered in

stratovolcano A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and per ...

cones, giving the volcano a maximum altitude of meters. Unlike its neighbour Karthala, La Grille does not have

caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is ...

. Different eruptive

vents Vent or vents may refer to: Science and technology Biology *Vent, the cloaca region of an animal *Vent DNA polymerase, a thermostable DNA polymerase Geology *Hydrothermal vent, a fissure in a planet's surface from which geothermally heated water ...

are located along the fissures that run along the volcano from north to south, parallel to the ridge of the mountain, and other cracks along the coast. Lava basalt sometimes escapes from these eruptive vents, sometimes reaching the sea to the east, north and west sides of the volcano. Many lava flows are still visible as few are rapidly recolonized by tropical Coconut trees on the island.

Important Bird Area

An 8,725 ha tract encompassing the higher slopes and summit of the mountain has been designated an

Important Bird Area An Important Bird and Biodiversity Area (IBA) is an area identified using an internationally agreed set of criteria as being globally important for the conservation of bird populations. IBA was developed and sites are identified by BirdLife Int ...

(IBA) by

BirdLife International BirdLife International is a global partnership of non-governmental organizations that strives to conserve birds and their habitats. BirdLife International's priorities include preventing extinction of bird species, identifying and safeguarding ...

because it supports populations of

Comoro olive pigeon The Comoros olive pigeon (''Columba pollenii''), also known as the Comoro olive pigeon, is a species of bird in the family Columbidae. It is found in Comoros and Mayotte. It is becoming rare due to habitat loss. Description Easily distinguisha ...

Comoro blue pigeon The Comoros blue pigeon (''Alectroenas sganzini'') is a species of bird in the family Columbidae. It is endemic to the Comoros and the coralline Seychelles. It is rated as a species of near threatened on the International Union fo ...

Malagasy harrier The Malagasy harrier (''Circus macrosceles'') is a bird of prey belonging to the marsh harrier group of harriers. It inhabits Madagascar and the Comoro Islands in the Indian Ocean. It was formerly regarded as a subspecies of the Réunion harrie ...

Grand Comoro brush warbler The Grand Comoro brush warbler (''Nesillas brevicaudata'') is a species of Old World warbler in the family Acrocephalidae. It is found in Comoros and Mayotte. Its natural habitat is subtropical or tropical moist montane forest Montane ecosys ...

s, Grand Comoro bulbuls, Comoro thrushes,

Humblot's sunbird Humblot's sunbird (''Cinnyris humbloti'') is a species of bird in the family Nectariniidae. It is endemic to the islands of Grand Comoro and Mohéli in the Comoros. Description The adult male Humblot's sunbird has green upperparts with a dark or ...

s and red-headed fodies.

References

Volcanoes of the Comoros Polygenetic shield volcanoes Hotspot volcanoes Important Bird Areas of the Comoros {{Comoros-geo-stub