Fumaroles active 35 years ago now emitting water vapor at 86°C

Izalco's summit crater was visited to examine the fumarole field that was the site of many geochemical and mineralogical studies in the 1960's and 1970's. The remaining fumaroles consist only of water vapor with a maximum temperature of 86°C.

Volcan de Izalco originated in 1770 A.D. on the S flank of Santa Ana volcano. Frequent Strombolian eruptions from the volcano, known as the "Lighthouse of Central America," produced a 650-m-high stratovolcano within 200 years.

Information Contacts: Alain Bernard, BRUGEL, Université Libre de Bruxelles 160/02 50, Ave. Roosevelt, 1050 Brussels, Belgium.

Information is preliminary and subject to change. All times are local (unless otherwise noted)

February 1974 (CSLP 21-74)

Thermal anomaly detected in 1973

Card 1792 (07 February 1974) Thermal anomaly detected in 1973

Remote infrared thermal patterns have been measured on the northeast flank . . . four times since December 1969. The sensor station is on Cerro Cerde at a distance of 1,100 m from Izalco. On 7 July 1973, a thermal anomaly appeared near the summit in a region that had been thermally inactive in earlie infrared studies. The anomaly stretched downslope about 50 m and covered an area about 1,000 m². The highest of the anomalous apparent surface etemperatures was 15°C, 2° above ambient. Data just processed from the 24 November 1973 observations show the anomaly expanded to the east to cover about 5,000 m². The most intense apparent surface temperatures occur in the same spot as the earlier pattern and register 19°C, 8° above ambient. The anomaly was intensified. The appearance and intensification of a thermal anomaly at Izalco indicates a change in the thermal regime of the volcano. The temperatures of the summit fumaroles were not unusually high in December 1973. The concentration of intermediate-depth earthquakes just south of Izalco was unusually high for the period 1971-72, as compared to 1967-70. Geophysical observations of these anomalous events are continuing.

Izalco last erupted in October-November 1966, with a lava flow from its south flank. Prior to that it had undergone intermittent lava and pyroclastic eruptions from 1770 to 1956, building up a composite cone 650 m above its base.

Information Contacts: Richard Birnie, Harvard University, Cambridge, MA; Ian Lange, Department of Geology, University of Montana, Missoula, MT; R. E. Stoiber, Department of Earth Sciences, Dartmouth College, Hanover, NH.

February 1999 (BGVN 24:02) Cite this Report

Strong fumarolic activity around the summit crater

During fieldwork on Santa Ana volcano in February, increased steaming was observed at the summit of Izalco relative to levels of previous years. Strong fumarolic activity occurred along the entire circumference of the 250-m-wide summit crater, with the exception of the NE side facing Cerro Verde. Activity was most vigorous at a vent on the N side of the crater floor, but was also strong along much of the inner rim of the crater and along its outer flanks. Steaming was observed over broad areas on the outer southern flanks to ~50 m below the rim, and on the W flank immediately N of a shoulder of the cone at ~1,800 m elevation, roughly 150 m below the summit. Activity had earlier been noticed to have increased in November 1998 following Hurricane Mitch. Most of the steaming was water vapor, and the increased activity was attributed to saturation of the still-warm cone by heavy rains accompanying the hurricane.

Information Contacts: Carlos Pullinger, Calle Padres Aguilar 448, Colonia Escalon, San Salvador, El Salvador; Demetrio Escobar, Centro de Investigaciones Geotecnicas (CIG), Final Blvd. Venezuela y calle a La Chacra, Apdo. Postal 109, San Salvador, El Salvador; Lee Siebert and Paul Kimberly, Global Volcanism Program, Smithsonian Institution.

December 1999 (BGVN 24:12) Cite this Report

Fumaroles active 35 years ago now emitting water vapor at 86°C

Izalco's summit crater was visited to examine the fumarole field that was the site of many geochemical and mineralogical studies in the 1960's and 1970's. The remaining fumaroles consist only of water vapor with a maximum temperature of 86°C.

Volcan de Izalco originated in 1770 A.D. on the S flank of Santa Ana volcano. Frequent Strombolian eruptions from the volcano, known as the "Lighthouse of Central America," produced a 650-m-high stratovolcano within 200 years.

Information Contacts: Alain Bernard, BRUGEL, Université Libre de Bruxelles 160/02 50, Ave. Roosevelt, 1050 Brussels, Belgium.