Report on Machin (Colombia) — 23 January-29 January 2008
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 23 January-29 January 2008
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2008. Report on Machin (Colombia). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 23 January-29 January 2008. Smithsonian Institution and US Geological Survey.
4.487°N, 75.389°W; summit elev. 2749 m
All times are local (unless otherwise noted)
Observatory Vulcanológico and Sismológico de Manizales reported unusual seismicity at Machín during 6-8 January. Long-period earthquakes were detected S of the main lava dome. On 7 January, volcano-tectonic seismic signals were registered and occasionally felt and reported by near by residents. The simultaneous occurrence of both types of seismic signals was unusual for Machín.
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.