Miravalles

Photo of this volcano
  • Country
  • Volcanic Region
  • Primary Volcano Type
  • Last Known Eruption
  • 10.748°N
  • 85.153°W

  • 2028 m
    6652 ft

  • 345030
  • Latitude
  • Longitude

  • Summit
    Elevation

  • Volcano
    Number

Most Recent Bulletin Report: October 1997 (BGVN 22:10) Citation IconCite this Report


Significant earthquake swarm under S flank

The most significant earthquake swarm at Miravalles in several years occurred on the S flank during 5-27 October (figure 2). The swarm, consisting of 146 located events, was centered around 10.7°N, 85.15°W. No pattern was found correlating the seismity with known local faults.

Figure (see Caption) Figure 2. Major faults in the Guanacaste Range of Costa Rica and October earthquake locations around Miravalles and Tenorio volcanoes. During 5-27 October, 620 earthquakes were recorded, but only 187 could be located. Courtesy of ICE.

Approximately 88% of the earthquakes were M <2, 11% were M 2-3, and 1% were M 3-3.3. Some earthquakes were felt by nearby residents. Seismic swarms and earthquakes of M >5.0 are not rare near Miravalles; however, the occurrence of two unrelated swarms nearby at Tenorio (~16 km ESE) during October was unusual.

Information Contacts: Gerardo J. Soto and Waldo Taylor, Oficina de Sismología y Vulcanología, Departamento de Geología, Instituto Costarricense de Electricidad (ICE), Apartado 10032-1000, San José, Costa Rica.

The Global Volcanism Program has no Weekly Reports available for Miravalles.

Bulletin Reports - Index


Reports are organized chronologically and indexed below by Month/Year (Publication Volume:Number), and include a one-line summary. Click on the index link or scroll down to read the reports.

09/1994 (BGVN 19:09) Summary of April 1991-July 1994 seismicity

10/1997 (BGVN 22:10) Significant earthquake swarm under S flank




Information is preliminary and subject to change. All times are local (unless otherwise noted)


September 1994 (BGVN 19:09) Citation IconCite this Report


Summary of April 1991-July 1994 seismicity

"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. The monthly number of recorded earthquakes at the Miravalles Caldera from April 1991 through July 1994 is shown on figure 1. Maximum magnitudes were 3.5; no high-magnitude local earthquakes occurred within the geothermal field during this study period. Previous seismological campaigns showed a similar level of activity.

Figure (see Caption) Figure 1. Monthly number of earthquakes recorded within the Miravalles Caldera, April 1991-July 1994. Courtesy of R. Barquero, ICE.

"The 219 tectonic events located during this period were distributed within a radius of 15 km of the geothermal field. There were some clusters of events that from their location and alignment could be correlated to previously determined faults and structures in the area and they were cataloged in 8 groups. Earthquakes recorded during the monitoring campaign were mostly shallow, with depths of 0-15 km and predominantly 0-5 km. 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."

Information Contacts: R. Barquero, ICE.


October 1997 (BGVN 22:10) Citation IconCite this Report


Significant earthquake swarm under S flank

The most significant earthquake swarm at Miravalles in several years occurred on the S flank during 5-27 October (figure 2). The swarm, consisting of 146 located events, was centered around 10.7°N, 85.15°W. No pattern was found correlating the seismity with known local faults.

Figure (see Caption) Figure 2. Major faults in the Guanacaste Range of Costa Rica and October earthquake locations around Miravalles and Tenorio volcanoes. During 5-27 October, 620 earthquakes were recorded, but only 187 could be located. Courtesy of ICE.

Approximately 88% of the earthquakes were M <2, 11% were M 2-3, and 1% were M 3-3.3. Some earthquakes were felt by nearby residents. Seismic swarms and earthquakes of M >5.0 are not rare near Miravalles; however, the occurrence of two unrelated swarms nearby at Tenorio (~16 km ESE) during October was unusual.

Information Contacts: Gerardo J. Soto and Waldo Taylor, Oficina de Sismología y Vulcanología, Departamento de Geología, Instituto Costarricense de Electricidad (ICE), Apartado 10032-1000, San José, Costa Rica.

Eruptive History


Summary of Holocene eruption dates and Volcanic Explosivity Indices (VEI).


Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
1946 Sep 14 1946 Sep 14 Confirmed 1 Historical Observations SW flank (near Las Hornillas)
5050 BCE (?) Unknown Confirmed   Tephrochronology

This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.

Photo Gallery


Vigorous mud eruptions occur at Las Hornillos thermal area on the west flank of Costa Rica's Miravalles volcano. A geothermal project in the 15 x 20 km Guayabo caldera (inside which Miravalles volcano was constructed) provides a major component of the electrical power needs of Costa Rica.

Photo by William Melson, 1988 (Smithsonian Institution)
See title for photo information.
Miravalles (or Neo-Miravalles) stratovolcano rises above the floor of the Guayabo caldera and is the youngest feature of the Miravalles volcanic complex. It, along with Paleo-Miravalles volcano, was constructed within a caldera left by collapse of Cerro Cabro Muco volcano about 200,000 years ago. Cabro Muco volcano was itself constructed within the 15 x 20 km wide Guayabo caldera, which was formed during a major explosive eruption sometime between 1.5 million and 600,000 years ago.

Photo by Guillermo Alvarado, 1985 (Instituto Coastarricense de Electricidad).
See title for photo information.
Miravalles volcano rises above a thermal area on its SW flank. The 2028-m-high andesitic stratovolcano is one of five post-caldera cones constructed 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. The only reported historical eruptive activity was a small steam explosion in 1946, although high heat flow remains, and a producing geothermal field is located within the caldera.

Photo by William Melson, 1988 (Smithsonian Institution)
See title for photo information.
Electrical power from the Miravalles geothermal plant is distributed from the control room of Project CORTEZ. The Miravalles I and II wells produce 60 and 55 MW of power, respectively, through reinjection. The vapor-phase Miravalles III well is expected to produce 27.5 MW. The depths of the geothermal wells vary from 959 to 3022 m.

Photo by Guillermo Alvarado (Instituto Costarricense de Electricidad).
See title for photo information.
The OSIVAM observatory that monitors seismic and volcanic activity at Arenal and Miravalles volcanoes is operated by the Department of Geology of the Instituto Costarricense de Electricidad (ICE). The observatory is located in Quebrada Grande, 14 km from the town of Tilarán, west of Lake Arenal.

Photo by Guillermo Alvarado (Instituto Costarricense de Electricidad).
See title for photo information.
A large area of irregular topography with many depressions containing small ponds is located south of Miravalles volcano along the road to the town of La Fortuna (not to be confused with La Fortuna near Arenal volcano). Large boulders, such as those in the foreground, are abundant. This topography is typical of that resulting from large volcanic debris avalanches and represents material produced by a major edifice collapse of the Miravalles volcanic complex.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
See title for photo information.
Steam plumes pour in 1998 from power plants of the Miravalles geothermal project, which began production in 1994 with an energy potential of 55 MW. By 1996 the plant was estimated to provide about 10% of the electrical power of Costa Rica.

Photo by Paul Kimberly, 1998 (Smithsonian Institution).
See title for photo information.
The remote northern side of the youngest cone of the Miravalles volcanic complex is covered with dense rain forest. Prior to the arrival of the Spanish, Miravalles was known by indigenous people as Cuipilapa, a Nahuatl term meaning "river of many colors," a reference to minerals dissolved in rivers draining the volcano. In clear weather the summit provides views extending to the Gulf of Nicoya and the savannas of Guanacaste.

Photo by Eliecer Duarte (OVSICORI-UNA).
See title for photo information.

Smithsonian Sample Collections Database


The following 45 samples associated with this volcano can be found in the Smithsonian's NMNH Department of Mineral Sciences collections. Catalog number links will open a window with more information.

Catalog Number Sample Description
NMNH 116066-173 Tephra
NMNH 116066-174 Soil
NMNH 116066-175 Biotite ignimbrite
NMNH 116066-176 Tephra
NMNH 116066-177 Tephra
NMNH 116066-178 Tephra
NMNH 116066-179 Tephra
NMNH 116066-180 Tephra
NMNH 116066-181 Tephra
NMNH 116066-182 Tephra
NMNH 116066-183 Tephra
NMNH 116066-184 Tephra
NMNH 116066-185 Tephra
NMNH 116066-186 Tephra
NMNH 116066-187 Soil
NMNH 116066-188 Tephra
NMNH 116066-189 Tephra
NMNH 116066-190 Tephra
NMNH 116066-192 Tephra
NMNH 116066-193 Tephra
NMNH 116066-194 Andesite
NMNH 116066-318 Soil
NMNH 116066-319 Clay
NMNH 116066-320 Soil
NMNH 116066-321 Clay
NMNH 116066-322 Basaltic andesite
NMNH 116066-323 Soil
NMNH 116066-324 Vitrophyre
NMNH 116066-325 Soil
NMNH 116066-326 Poorly-sorted pyroclastic-rock
NMNH 116066-327 Soil
NMNH 116066-328 Soil
NMNH 116066-329 Poorly-sorted pyroclastic-rock
NMNH 116066-330 Xenolithic
NMNH 116066-376 Pumice
NMNH 116066-377 Unidentified
NMNH 116066-378 Pumice
NMNH 116066-379 Volcanic
NMNH 116066-380 Unidentified
NMNH 116066-381 Unidentified
NMNH 116066-382 Unidentified
NMNH 116066-383 Unidentified
NMNH 116066-384 Unidentified
NMNH 116066-385 Unidentified
NMNH 116066-386 Unidentified

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