Geologic Background:
Caulle and its larger neighbor, Puyehue,
immediately to the south, are located approximately 80 km
east of the city of Osorno and just north of Highway 215,
one of the main routes between Chile and Argentina. The
volcano is host to hot springs and fumaroles. Caulle is
rhyodacitic in composition and its eruptions have been
explosive in the past. There is no permanent ice on the
edifice, but remaining winter snow provides some concern
about the potential for mudflows.
Cordon Caulle is a group of post-caldera silicic vents
formed along a 17-km-long, 2.5-km-wide WNW-ESE rift zone
extending to the SE from the Pleistocene Cordillera
Nevada caldera towards Puyehue volcano. Some of the
Cordon Caulle vents occur within the Cordillera
Nevada Caldera, while others are outside the caldera.
The Cordillera Nevada caldera is the only known source of
rhyolitic tuff in the southern Andes. It is not known if
magma of the Cordon Caulle group is related to any
beneath the Cordillera Nevada Caldera. Recent lavas of
the Cordon Caulle group are dacitic, but subordinate
basalt was erupted in the early development of this group
of vents. Although Cordon Caulle is sometimes listed as
part of Puyehue volcano, it is tectonically and
magmatically distinct from Puyehue.
The Cordon Caulle fissures lie just west of the
Liquine-Reloncavi line, a major N10°E strike-slip
fault that spans much of the length of the south- central
Chilean volcanic belt. They also lie at the apex of two
segments of a conjugate set of N60°E and N50°W
faults that are at least in part tension features
associated with movement along the Liquine-Reloncavi
Fault. Many of the volcanoes in this area, including
Cordillera Nevada center, the Cordon Caulle fissures, and
Puyehue, have grown along this set of conjugate
faults.
Historic Activity:
- Historical eruptions have occurred from several
points along the Cordon Caulle fissure system during the
19th and 20th centuries.
- Simultaneous eruptions of dacite lava from several
fissure vents occurred in 1921-22. The 1921-22 eruption
began with explosive activity on Dec. 13, 1921. Ash and
pumice were produced in great quantity, after earthquakes
and a deafening roar. Further explosions on Dec. 19-21,
sent ash 62 km high. Ash fell in La Plata, 3000 km to the
northeast, and was seen over Europe and southwest Africa.
Lava extrusion began in February 1922.
- A small eruption occurred in 1934, after an
earthquake.
Recent Activity:
- The 1960 eruption is one of the best documented
examples of an eruption triggered by a tectonic
earthquake. A M=8.3 earthquake occurred on May 22, 1960,
some 300 km northwest of the Cordillera Nevada Caldera,
and a strong explosive eruption began approximately 48
hours later, followed by extrusion of lava. Dacitic lava
was extruded from multiple vents along a 14 km long set
of NW-SE trending fissures. From the start of the
eruption, and continuing for 6 days, ash obscured the
sky. The eruption ended on June 25, 1960 after the
extrusion of several lava flows.
- A series of small to moderate felt earthquakes and
discontinuous subterranean noises occurred during the
last week of May, 1994.
Data Sources:
- Global Volcanism Network (V. 19, No. 5).
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