Report on Arenal (Costa Rica) — 3 September-9 September 2003
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
3 September-9 September 2003
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2003. Report on Arenal (Costa Rica). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 3 September-9 September 2003. Smithsonian Institution and US Geological Survey.
10.463°N, 84.703°W; summit elev. 1670 m
All times are local (unless otherwise noted)
A sequence of pyroclastic flows began at Arenal on 5 September at 1055. Seismographs recorded eight signals within 2 hours after the activity began. Lava flows descended to 800 m down the volcano's N and NE flanks. Ash drifted towards the W and NW. No injuries or deaths were reported and the main effects were limited to the National Park boundaries.
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.