Volcán Cerro Machín, Stratovolcano in Tolima Department, Colombia.

Cerro Machín is a stratovolcano on the eastern flank of the Central Cordillera that rises to 2,650 meters and holds a crater measuring 2.4 kilometers across. Inside this crater sit three dacite domes that shape the volcanic landscape.

Six eruptive episodes are known from the Holocene, dated from charred wood at 5,000, 4,800–4,300, 3,600, 2,500, 1,200 and 800 years before present; four were Plinian and two came from dome collapse. The last eruption, around 800 AD, left the scar of the most recent dome. Some link the volcano to the 1687 "Tiempo del Ruido", when sulphur gases panicked Bogotá; seismic activity resumed in 2000.

The name Machín is shared with the surrounding village and hot springs, and the volcano's crater holds a small lagoon ringed by five domes. Farmers in the Coello and Toche river basins work land whose soils derive from the volcano's ash and lahar deposits, and the 2008 seismic crisis led some 450 families from Toche and nearby hamlets to move toward Cajamarca and Ibagué.

Access requires a 4x4 vehicle to handle the unpaved road from Ibagué that climbs steeply through narrow mountain paths. The drive can take several hours depending on weather, so plan to leave early in the morning.

An active hydrothermal system generates fumaroles and thermal springs across the volcano, while ongoing microseismic activity signals underground magma movement. Measurements have also detected elevated radon concentrations around the crater area.