Geologic Background:
A large basaltic to dacitic volcanic complex on
the Chile-Argentina border. Planchon-Peteroa is a complex
volcano with several overlapping calderas. The structure
of the edifice is complicated by at least 2 syn-volcanic
glaciations and a large debris avalanche (the "Teno
Lahar") that removed a sector of Planchon. Activity began
in the Pleistocene with construction of Volcan Azufre,
followed by formation of Volcan Planchon, 6 km to the
north. About 11,500 years ago, much of Azufre and part of
Planchon collapsed, forming the massive Rio Teno debris
avalanche, which reached Chile's Central Valley.
Subsequently, Volcan Planchon II was formed. The youngest
volcano, Volcan Peteroa, consisting of scattered vents
between Azufre and Planchon, has been active into
historical time and contains a small steaming crater
lake.
Historic Activity:
- Eruptions in 1762 and 1889-1894.
- Historical eruptions have been dominantly explosive,
although lava flows were erupted in 1837 and 1937.
- Historic activity has occurred in a 500-m-diameter
crater between the cones of Planchon (3977 m) and Peteroa
(4,101 m).
- The most recent lava flow was erupted in Feb.
1937.
- Explosive activity during 1959, 1960, and 1967.
Recent Activity:
- A tephra eruption began on February 9, 1991.
- Strong fumarolic activity and small phreatic
eruptions produced minor ashfall in November 1998.
- Increased fumarolic activity in early 2001
Data Sources:
- Global Volcanism Network (V. 16, No. 1 and V. 26, No.
3).
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