The Almolonga volcano, also called "Cerro Quemado" (Burned Mountain) or "La Muela" (The Molar) due to its distinct shape, is an

andesitic Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predomin ...

stratovolcano in the south-western department of

Quetzaltenango Quetzaltenango (, also known by its Maya name Xelajú or Xela ) is both the seat of the namesake Department and municipality, in Guatemala. The city is located in a mountain valley at an elevation of above sea level at its lowest part. It m ...

in Guatemala. The volcano is located near the town of Almolonga, just south of

, Guatemala's second largest city. The volcano is set along the Zunil fault zone and has a central caldera surrounded by several

dacitic Dacite () is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyol ...

and

rhyolitic Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained groundmass. The mineral ...

lava domes and formed in a

back-arc A back-arc basin is a type of geologic basin, found at some convergent plate boundaries. Presently all back-arc basins are submarine features associated with island arcs and subduction zones, with many found in the western Pacific Ocean. Most o ...

volcanic setting, with activity commencing 84,000BP. Almolonga stratovolcano is the oldest edifice and underwent collapse prior to the caldera forming eruption of Lake Atitlan, the major chronological marker of volcanism in the region. The collapse of the stratovolcano left a

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 ...

with a diameter of 3,3 km and a depth of 350m that was subsequently occupied by lava domes on its northern edge and covered by

tephra Tephra is fragmental material produced by a volcanic eruption regardless of composition, fragment size, or emplacement mechanism. Volcanologists also refer to airborne fragments as pyroclasts. Once clasts have fallen to the ground, they re ...

layers from numerous volcanoes, both in the Almolonga field and others. Cerro Quemado is the largest (about 2 km³) and youngest lava dome complex formed by eight vents with viscous lava flows and plugs during four distinct volcanic phases - the first two involving effusion of lava and formation of new domes. Cerro Quemado underwent a flank collapse 1,150BP, generating a landslide that went 6 km SSW in the Llano de Pinal valley and occupied an area of 13 km², generating a lateral blast that affected the neighbouring Volcán Siete Orejas volcano as well. A lava dome emerged inside the collapse scar subsequently. 1818 an eruption formed a block lava flow over half a year that travelled 2.5 km eastward. Lahars and further explosive activity are potential hazards from this volcano.

References

* * * Stratovolcanoes of Guatemala Subduction volcanoes Mountains of Guatemala Pleistocene stratovolcanoes Holocene stratovolcanoes {{Guatemala-geo-stub

See also

References