According to INGEOMINAS, Observatory Vulcanológico and Sismológico de Manizales reported that at 0732 on 9 September a M 3.6 volcano-tectonic earthquake occurred below the main lava dome at Cerro Machín at a depth of 3.2 km, and was felt by nearby residents. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").

Geological Summary. The small Cerro Machín stratovolcano lies at the southern end of the Ruiz-Tolima massif about 20 km WNW of the city of Ibagué. A 3-km-wide caldera is breached to the south and contains three forested dacitic lava domes. Voluminous pyroclastic flows traveled up to 40 km away during eruptions in the mid-to-late Holocene, perhaps associated with formation of the caldera. Late-Holocene eruptions produced dacitic block-and-ash flows that traveled through the breach in the caldera rim to the west and south. The latest known eruption of took place about 800 years ago.

Source: Servicio Geológico Colombiano (SGC)