Report on Arenal (Costa Rica) — August 1990
Bulletin of the Global Volcanism Network, vol. 15, no. 8 (August 1990)
Managing Editor: Lindsay McClelland.
Arenal (Costa Rica) More frequent explosions; lava flow remains active
Please cite this report as:
Global Volcanism Program, 1990. Report on Arenal (Costa Rica). In: McClelland, L (ed.), Bulletin of the Global Volcanism Network, 15:8. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199008-345033.
10.463°N, 84.703°W; summit elev. 1670 m
All times are local (unless otherwise noted)
An average of 24 explosions/day, with a maximum of 41 (12 August), were recorded during August; June and July averaged 20 explosions/day. The Strombolian explosions ejected material to 1,000 m above the crater. "Fountains of bombs," without corresponding explosions, were noted 14 and 17 August. In addition to the explosions, tremor activity increased, especially between 17 and 21 August. Crater gas emissions appeared to be water-rich and an active lava flow on the NW flank reached 1,200 m elevation.
Geologic Background. 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: G. Soto, ICE.