Report on Arenal (Costa Rica) — November 1997
Bulletin of the Global Volcanism Network, vol. 22, no. 11 (November 1997)
Managing Editor: Richard Wunderman.
Arenal (Costa Rica) January-November tremor and earthquakes
Please cite this report as:
Global Volcanism Program, 1997. Report on Arenal (Costa Rica) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 22:11. Smithsonian Institution.
10.463°N, 84.703°W; summit elev. 1670 m
All times are local (unless otherwise noted)
Seismicity for Arenal during January through November 1997 is shown on figure 83. The monthly earthquake count peaked in July at around 1,600 events, but many months had fewer than 600. Tremor reached durations of 250-300 hours during January, March, and June.
|Figure 83. Arenal's monthly earthquake count and tremor duration for the interval January-October 1997. Data were registered at station "VACR," 2.7 km NE of the main crater. Courtesy of OVSICORI-UNA|
Arenal's first historical eruption, in mid-1968, began an unbroken sequence of Strombolian explosions and lava effusion from multiple vents. Since then the volcano has erupted material of basaltic-andesite composition.
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: E. Fernandez, R. Van der Laat, F. de Obaldia, T. Marino, V. Barboza, W. Jimenez, R. Saenz, E. Duarte, M. Martinez, E. Hernandez, and F. Vega, Observatorio Vulcanologico y Sismologico de Costa Rica, Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica.