Sumaco is a symmetrical, isolated

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

, that is set off from the main

Ecuador Ecuador, officially the Republic of Ecuador, is a country in northwestern South America, bordered by Colombia on the north, Peru on the east and south, and the Pacific Ocean on the west. It also includes the Galápagos Province which contain ...

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

Andean The Andes ( ), Andes Mountains or Andean Mountain Range (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long and wide (widest between 18°S ...

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 calcic plagioclase and forms from magma low in silica and enriched in alkali metal ox ...

and

phonolitic Phonolite is an uncommon shallow intrusive or 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 var ...

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 only 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 foun ...

. There are also a number of endemic animals, including toad '' Osornophryne sumacoensis'' only known from the eastern slopes of Sumaco, and robber frog '' Pristimantis ernesti'' only known from the summit of Sumaco.

References

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