Aliso, also known as Pan de Azúcar, is a volcano in the Ecuadorian Andes to the east of

Antisana Antisana is a stratovolcano of the northern Andes, in Ecuador. It is the fourth highest volcano in Ecuador, at , and is located SE of the capital city of Quito. Antisana presents one of the most challenging technical climbs in the Ecuadorian A ...

volcano. The complex contains a semicircular western ridge and lava domes. The volcano has erupted

rhyolite 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 ...

s and

dacite 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 rhyolite. ...

s and some

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 predomina ...

lava flows on a ridge above Baeza. It is covered with

tundra In physical geography, tundra () is a type of biome where tree growth is hindered by frigid temperatures and short growing seasons. The term ''tundra'' comes through Russian (') from the Kildin Sámi word (') meaning "uplands", "treeless moun ...

and

cloud forest A cloud forest, also called a water forest, primas forest, or tropical montane cloud forest (TMCF), is a generally tropical or subtropical, evergreen, montane, moist forest characterized by a persistent, frequent or seasonal low-level cloud c ...

s. At least two eruptions of Pumayacu occurred during the

Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togethe ...

; one dated 4400 years ago and another's lapilli deposits overlie a cultural horizon 2000 years old. Older eruptions have been dated at 1.15 ± 0.07 Ma and are of high-

potassium Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosphe ...

types. They compromise typical arc-derived lavas with

fractional crystallization Fractional crystallization may refer to: * Fractional crystallization (chemistry), a process to separate different solutes from a solution * Fractional crystallization (geology) Fractional crystallization, or crystal fractionation, is one of the ...

and other differentiation processes.

References

Volcanoes of Ecuador Andean Volcanic Belt Inactive volcanoes {{Volcano-stub