Sumaco is a symmetrical, isolated

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 ...

, that is set off from the main

Ecuador Ecuador ( ; ; Quechua: ''Ikwayur''; Shuar: ''Ecuador'' or ''Ekuatur''), officially the Republic of Ecuador ( es, República del Ecuador, which literally translates as "Republic of the Equator"; Quechua: ''Ikwadur Ripuwlika''; Shuar: ''Eku ...

volcanic axis. Its rocks are very distinct from those from most

Andean The Andes, Andes Mountains or Andean Mountains (; ) are the List of mountain ranges#Mountain ranges by length, longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range i ...

volcanoes because of its lack of

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 ...

composition, in favour of

basanite Basanite () is an igneous, volcanic (extrusive) rock with aphanitic to porphyritic texture. It is composed mostly of feldspathoids, pyroxenes, olivine, and plagioclase and forms from magma low in silica and enriched in alkali metal oxides that s ...

and

phonolitic Phonolite is an uncommon extrusive rock, of intermediate chemical composition between felsic and mafic, with texture ranging from aphanitic (fine-grained) to porphyritic (mixed fine- and coarse-grained). Phonolite is a variation of the igneous ...

rock. Sumaco is heavily forested and contains a small cone in its broad summit crater. An historical eruption occurred around 1895 (± 30 years).

Ecology

Sumaco is isolated from the Cordillera Oriental by the lowland valley of the Cosanga and Quijos Rivers. There are more than 6000 species of vascular plants, including more than 90

endemic species Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

. There are also a number of endemic animals, including toad ''

Osornophryne sumacoensis ''Osornophryne sumacoensis'' is a species of toad in the family Bufonidae. It is endemic to the Ecuador and only found in the forests surrounding a small crater lake on the eastern slopes of Sumaco, a volcano in the Napo Province. Description ' ...

'' only known from the eastern slopes of Sumaco, and robber frog ''

Pristimantis ernesti ''Pristimantis ernesti'' is a species of frog in the family Strabomantidae. It is endemic to the summit of Sumaco, a volcano in the Napo Province, Ecuador. Its common name is Ernest's robber frog. It is named after Dr. Ernst Williams, a friend ...

'' only known from the summit of Sumaco.

References

Stratovolcanoes of Ecuador Andean Volcanic Belt Three-thousanders of the Andes {{volcano-stub