Andean Volcanic Belt

The Andean Volcanic Belt runs along Chile, Bolivia, Colombia, Ecuador, Peru, and Argentina. Aracar Volcano
The Volcanic Belt came to be because of convergence, the Antarctic Plate and Nazca Plate rubbing underneath the South American Plate. The formation began at the time of the Jurassic period, but the Andes as we know them did not come to be until the Cretaceous

There are four main zones of the Andean Volcanic Belt. They are the Northern, Central, Southern, and Austral volcanic zones. These zones are considered to be the active regions in the Andes. The active regions are separated by volcanic gaps, zones lacking volcanic activity. These gaps are the Peruvian, Pampean, and the Patagonian gaps.
Most of the Andes volcanoes are stravolcanoes/composite volcanoes. Composite volcanoes occur because of subduction zones, in this case the Antarctic and Nazca plates colliding with the South American plate. They are made from lava, cinders, and ash. The volcanoes are composed of andesite.
The Nevado Del Ruiz volcano, located in the northern part of the Andes in Colombia, is known to be active. This volcano has a summit elevation of 5,389 m, and is covered with 25 km2 of snow and ice. The eruptions from this volcano produce lahars. A lahar is a volcanic mudflow created due to melting snow or ice from a an eruption. Lahars can become deadly because of the mudflow the melting snow creates. On November 13, 1985, Nevado Del Ruiz erupted, and created a lahar. The lahar came down on the city of Armero, killing most of its' residents.

To this day, the Nazca and Antarctic plate are still subducting with the South American plate. Because of this, earthquakes and volcanic eruptions such as the one in 1985 still occur.