Report on Machin (Colombia) — 1 December-7 December 2010
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 1 December-7 December 2010
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2010. Report on Machin (Colombia). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 1 December-7 December 2010. Smithsonian Institution and US Geological Survey.
4.487°N, 75.389°W; summit elev. 2749 m
All times are local (unless otherwise noted)
According to INGEOMINAS, Observatory Vulcanológico and Sismológico de Manizales reported increased seismicity from Cerro Machín on 3 December. About 340 volcano-tectonic earthquakes with low magnitudes were located SW of the main lava dome, at an average depth of 4 km. The largest event, a M 3.7 earthquake located SW of the dome at a depth of about 3.5 km, was felt by local residents. The Alert level remained at III (Yellow; "changes in the behavior of volcanic activity").
Geologic Background. 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.