Conical Volcan Arenal is the youngest stratovolcano in Costa Rica and one of its most active. The 1657-m-high andesitic volcano towers above the eastern shores of Lake Arenal, which has been enlarged by a hydroelectric project. Arenal lies along a volcanic chain that has migrated to the NW from the late-Pleistocene Los Perdidos lava domes through the Pleistocene-to-Holocene Chato volcano, which contains a 500-m-wide, lake-filled summit crater. The earliest known eruptions of Arenal took place about 7000 years ago, and it was active concurrently with Cerro Chato until the activity of Chato ended about 3500 years ago. Growth of Arenal has been characterized by periodic major explosive eruptions at several-hundred-year intervals and periods of lava effusion that armor the cone.

Photo by Scott Rowland.

Arenal's most recent eruptive period began on July 29, 1968 at 7:20 AM when "Cerro" Arenal--as it was called by local residents--explosively blew the west side off the volcano. Two villages at the foot of the volcano-- Pueblo Nuevo and Tabacon--were completely destroyed and 78 people died. Between July 29 and 31 three new craters were formed on the western flank of the volcano and a fifteen-square kilometer area (5.8 square miles) was devastated.


Image Credit, tours and more photographs are available at:

Continuous explosive activity accompanied by slow lava effusion and the occasional emission of pyroclastic flows has occurred since then from vents at the summit and on the upper western flank.

Image Credit: Klaus Larsen Photography - For even more great images visit

Ancient footpaths around the Arenal Volcano dating from around 500 BC (2500 years ago!) were discovered by the NASA Archeological Remote Sensing Project. As a result of two overflights using a specially equipped Learjet a remote sensing database of the Arenal Region was created that included:
  • color and false-color infrared photographs
  • thermal data from TIMS
  • two bands of synthetic aperture radar data
  • light-detection and ranging (lidar) data
  • seven spectral bands from Landsat's Thematic Mapper

This was one of the most extensive remote sensing databases created for archeology to that time.

For more information, the NASA Archeological Remote Sensing Project.


Visit the Scripps Web site titled Volcano Expedition from the field in Costa Rica to follow a two-week-long

field trip to six active volcanic areas in the highlands of Costa Rica in Central America!!




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Costa Rica