Geologic Background:
Miravalles stratovolcano, located 34 km
eastsoutheast of Liberia in Costa Rica's north volcanic
arc, is a complex caldera structure that formed during
several pulses between 1.6 and 0.6 Ma. This 15 x 20 km
caldera contains five post-caldera cones along a
northeast-trending line. Miravalles is an andesitic
stratovolcano that is one of five post-caldera cones
along a NE-trending line within the Pleistocene, 15 x 20
km Miravalles caldera. Morphologically youthful lava
flows cover the western and SW flanks of the volcano.
Historic Activity:
- The only reported historical eruptive activity was a
small steam explosion in 1946.
- Several thermal springs and fumaroles are present at
the southwest foot of this volcano, and it is the site of
a geothermal field.
Recent Activity:
- The Office of Seismology and Volcanology of the
Department of Geological Engineering, Costa Rican
Institute of Electricity (ICE), has monitored the
seismicity of the Miravalles Geothermal Field since 1977.
During the period from April 1991 to July 1994, 219
tectonic events were distributed within a radius of 15 km
of the geothermal field. Maximum magnitudes were 3.5. The
distribution of earthquakes cannot be correlated with a
magma chamber or any shallow magmatic body in the area,
but it confirms that some seismic activity is taking
place under and inside the caldera.
Data Sources:
- Global Volcanism Network (V. 19, No. 9 and V. 22, No.
20).
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