By May, visible activity was limited to a weak white plume from the summit crater. A seismic station (FG3), 5 km SE of the summit at 1,500 m altitude, registered 30 microearthquakes with S-P <= 2.0 seconds during May and 40 in June. On 8 June, residents of Guatemala City observed a white vapor column extending hundreds of meters above the summit. This coincided with an apparent earthquake swarm and a 10 microradian change on the electric tiltmeter installed in March at the same location as the seismic station (12:05). During the following days, INSIVUMEH personnel installed portable seismic stations 10 km E and W of the summit (at Alotenango and San Pedro Yepocapa). These did not register any seismicity. INSIVUMEH geologists suggested that heavy rains on 8 June may have been responsible for the observed activity.

Geological Summary. Volcán Fuego, one of Central America's most active volcanoes, is also one of three large stratovolcanoes overlooking Guatemala's former capital, Antigua. The scarp of an older edifice, Meseta, lies between Fuego and Acatenango to the north. Construction of Meseta dates back to about 230,000 years and continued until the late Pleistocene or early Holocene. Collapse of Meseta may have produced the massive Escuintla debris-avalanche deposit, which extends about 50 km onto the Pacific coastal plain. Growth of the modern Fuego volcano followed, continuing the southward migration of volcanism that began at the mostly andesitic Acatenango. Eruptions at Fuego have become more mafic with time, and most historical activity has produced basaltic rocks. Frequent vigorous historical eruptions have been recorded since the onset of the Spanish era in 1524, and have produced major ashfalls, along with occasional pyroclastic flows and lava flows.

Information Contacts: E. Sánchez, INSIVUMEH.