Logo link to homepage

Report on Arenal (Costa Rica) — May 1989


Scientific Event Alert Network Bulletin, vol. 14, no. 5 (May 1989)
Managing Editor: Lindsay McClelland.

Arenal (Costa Rica) Continued Strombolian activity; small nuees ardentes

Please cite this report as:

Global Volcanism Program, 1989. Report on Arenal (Costa Rica) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 14:5. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198905-345033


Costa Rica

10.463°N, 84.703°W; summit elev. 1670 m

All times are local (unless otherwise noted)

Arenal's Strombolian activity continued during the first 4 months of 1989. The number of small to moderate explosions increased in March, when a maximum of 42 daily volcanic earthquakes were recorded by the Instituto Costarricense de Electricidad (figure 19). Activity then gradually declined. Sporadic explosions continued in April, sometimes producing nuées ardentes that moved 800-1,000 m downslope, observed 6 April at 1341, and 12 April at 1134 and 1337. Lava extrusion was sporadic and the flows did not advance far.

Figure (see Caption) Figure 19. Number of volcanic earthquakes at Arenal, January-April 1989, recorded at the FOR station (Red Sismologica Nacional). Vigorous eruptive activity is marked by sketches of active cones; vertical arrows are minimum values indicating incomplete data (amplifier failure or masking by excessive volcanic noise); no data were collected during periods labeled "S.R." Courtesy of Rafael Barquero and Guillermo Alvarado, ICE.

Geological Summary. Conical Volcán Arenal is the youngest stratovolcano in Costa Rica and one of its most active. The 1670-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. An eruptive period that began with a major explosive eruption in 1968 ended in December 2010; continuous explosive activity accompanied by slow lava effusion and the occasional emission of pyroclastic flows characterized the eruption from vents at the summit and on the upper western flank.

Information Contacts: R. Barquero and G. Alvarado, ICE; J. Barquero, E. Fernández, and V. Barboza, OVSICORI.