Colachi, Stratovolcano in Antofagasta Region, Chile

Colachi is a stratovolcano in the Antofagasta Region that rises to 5,631 meters in elevation. The mountain displays a worn summit crater and visible lava flows streaming down its eastern slopes.

The volcano formed during the late Miocene period on elevated welded ignimbrites. It developed as part of a broader volcanic system alongside the nearby Acamarachi volcano.

Colachi is one of the stratovolcanoes lined along the eastern side of the Salar de Atacama, a chain whose most active member is Lascar. The name Colachi is used for the peak on Chilean maps and in the Spanish-language sources, alongside the nearby Acamarachi.

The remote location and extreme elevation require specialized climbing gear and detailed trip planning. Visitors must allow sufficient time to acclimatize to the altitude before attempting any ascent.

The 7 km² silicic lava flow on the saddle toward Acamarachi is not glassy obsidian but silica-rich lava, a composition that makes it viscous and slow-moving. Colachi itself was built on a basement of ignimbrites, welded tuff sheets that underlie the whole edifice.