Chimborazo

Geography & Climate

Chimborazo is located in Ecuador, within the Northern Andean Volcanic Arc of the broader South America Volcanic Regions. Situated at 1.47° S, 78.82° W in the Southern Hemisphere, the volcano lies within a tropical climate zone. At 6,261 meters above sea level, Chimborazo reaches well into the permanent snow and ice zone. Glaciers and snowpack on the upper slopes create the potential for lahars — destructive volcanic mudflows — during eruptions, as heat rapidly melts ice and snow. The volcanic landform is characterized as a composite, which describes the physical shape and structure of the volcanic edifice as observed from the surface.

Geological Context

Chimborazo sits in a subduction zone, where one tectonic plate dives beneath another, creating intense heat and pressure that generates magma. Subduction zones are responsible for many of the world's most explosive volcanoes and deadliest eruptions. For communities in Ecuador near Chimborazo, this tectonic setting means the volcano is capable of producing powerful explosive eruptions, pyroclastic flows, and lahars that can threaten populated areas within tens of kilometers of the summit. The dominant rock type is andesite / basaltic andesite, a dark, fine-grained volcanic rock that forms from rapidly cooling, low-viscosity lava. Basaltic eruptions tend to be less explosive and produce fluid lava flows that can travel long distances. While less immediately dangerous than explosive eruptions, basaltic lava flows can destroy structures and infrastructure in their path, and volcanic gases released during these eruptions can affect air quality over a wide area.

Eruption History Summary

Chimborazo has 6 recorded eruptions in the geological database, spanning from 7500 BCE to 550 CE. This eruption frequency indicates a moderately active volcanic system with periodic reawakenings.

Significance

With 6 recorded eruptions on file, Chimborazo has enough documented activity to help scientists identify patterns in its eruptive behavior.

GVP Reference Summary

Glacier-clad Chimborazo, Ecuador's highest volcano, anchors the southern end of the country's "Avenue of Volcanoes" 30 km NW of the city of Riobamba. The dominantly andesitic-to-dacitic structure is mostly of Pliocene-to-Pleistocene age. The volcano collapsed about 35,000 years ago, producing a major debris avalanche, whose deposits underlie Riobamba and temporarily dammed the Río Chambo, producing an ephemeral lake. Subsequent mainly been andesitic activity constructed three edifices along an E-W line, the youngest and westernmost of which forms the current summit. Although activity was at one time thought to have ceased during the very latest Pleistocene, recent work indicates that it erupted more than a half dozen times during the Holocene, producing pyroclastic surges that reached down to 3,800 m elevation.

— Smithsonian Institution, Global Volcanism Program