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Miravalles

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

  • 2028 m
    6654 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 M5.0 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 M5.0 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.

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.

Eruptive History

There is data available for 2 confirmed Holocene eruptive periods.

1946 Sep 14 - 1946 Sep 14 Confirmed Eruption Max VEI: 1

Episode 1 | Eruption Episode SW flank (near Las Hornillas)
1946 Sep 14 - 1946 Sep 14 Evidence from Observations: Reported

List of 4 Events for Episode 1 at SW flank (near Las Hornillas)

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Phreatic activity weak or small
   - - - -    - - - - Ash
   - - - -    - - - - Earthquakes (undefined) weak or small
1946 Sep 14    - - - - VEI (Explosivity Index)

5050 BCE (?) Confirmed Eruption  

Episode 1 | Eruption Episode
5050 BCE (?) - Unknown Evidence from Correlation: Tephrochronology

List of 1 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion
Deformation History

There is no Deformation History data available for Miravalles.

Emission History

There is no Emissions History data available for Miravalles.

Photo Gallery

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

Photo by William Melson, 1988 (Smithsonian Institution)
Miravalles, seen here looking NE from the Guayabo caldera floor, is the youngest feature of the volcanic complex. Multiple edifices have grown in the eastern part of the 15 x 20 km caldera, which formed sometime between 1.5 million and 600,000 years ago.

Photo by Guillermo Alvarado, 1985 (Instituto Coastarricense de Electricidad).
A geothermal area is seen here on the Miravalles SW flank in 1988. The edifice is one of five post-caldera cones constructed within the Pleistocene Guayabo caldera. Lava flows cover the W and SW flanks. A small steam explosion was reported in 1946 and a producing geothermal field is located within the caldera.

Photo by William Melson, 1988 (Smithsonian Institution)
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).
This is the OSIVAM observatory that monitors seismic and volcanic activity at Arenal and Miravalles volcanoes. The observatory is located in Quebrada Grande, 14 km from the town of Tilarán and west of Lake Arenal.

Photo by Guillermo Alvarado (Instituto Costarricense de Electricidad).
This topography south of Miravalles volcano is typical of that resulting from large volcanic debris avalanches and represents material produced by major edifice collapse. Large boulders are abundant, such as those in the foreground.

Photo by Lee Siebert, 1998 (Smithsonian Institution).
Steam plumes rise from power plants of the Miravalles geothermal project in 1998, which began production in 1994.

Photo by Paul Kimberly, 1998 (Smithsonian Institution).
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 descending the volcano.

Photo by Eliecer Duarte (OVSICORI-UNA).
GVP Map Holdings

The maps shown below have been scanned from the GVP map archives and include the volcano on this page. Clicking on the small images will load the full 300 dpi map. Very small-scale maps (such as world maps) are not included. The maps database originated over 30 years ago, but was only recently updated and connected to our main database. We welcome users to tell us if they see incorrect information or other problems with the maps; please use the Contact GVP link at the bottom of the page to send us email.

Smithsonian Sample Collections Database

The following 34 samples associated with this volcano can be found in the Smithsonian's NMNH Department of Mineral Sciences collections, and may be availble for research (contact the Rock and Ore Collections Manager). Catalog number links will open a window with more information.

Catalog Number Sample Description Lava Source Collection Date
NMNH 116066-173 Tephra -- 6 Mar 1985
NMNH 116066-175 Biotite Ignimbrite -- 6 Mar 1985
NMNH 116066-176 Tephra -- 6 Mar 1985
NMNH 116066-177 Tephra -- 6 Mar 1985
NMNH 116066-178 Tephra -- 6 Mar 1985
NMNH 116066-179 Tephra -- 6 Mar 1985
NMNH 116066-180 Tephra -- 6 Mar 1985
NMNH 116066-181 Tephra -- 6 Mar 1985
NMNH 116066-182 Tephra -- 6 Mar 1985
NMNH 116066-183 Tephra -- 6 Mar 1985
NMNH 116066-184 Tephra -- 6 Mar 1985
NMNH 116066-185 Tephra -- 6 Mar 1985
NMNH 116066-186 Tephra -- 6 Mar 1985
NMNH 116066-188 Tephra -- 6 Mar 1985
NMNH 116066-189 Tephra -- 6 Mar 1985
NMNH 116066-190 Tephra -- 6 Mar 1985
NMNH 116066-192 Tephra -- 6 Mar 1985
NMNH 116066-193 Tephra -- 6 Mar 1985
NMNH 116066-194 Andesite -- 6 Mar 1985
NMNH 116066-322 Basaltic Andesite -- 15 Mar 1985
NMNH 116066-324 Vitrophyre -- 15 Mar 1985
NMNH 116066-326 Ignimbrite -- 15 Mar 1985
NMNH 116066-329 Ignimbrite -- 15 Mar 1985
NMNH 116066-330 Xenolith -- 15 Mar 1985
NMNH 116066-376 Pumice -- --
NMNH 116066-377 Volcanic Debris -- --
NMNH 116066-378 Pumice -- --
NMNH 116066-379 Volcanic Rock -- 21 Apr 1985
NMNH 116066-381 Unidentified -- 21 Apr 1985
NMNH 116066-382 Unidentified -- 21 Apr 1985
NMNH 116066-383 lahar -- 21 Apr 1985
NMNH 116066-384 Andesitic Lava -- 21 Apr 1985
NMNH 116066-385 Flow Rock -- 21 Apr 1985
NMNH 116066-386 Andesitic Lava -- 21 Apr 1985
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