Intermittent emission of gray to black ash clouds continued through late May. Clouds and dense haze totally obscured the volcano for 11 days of the 25-day reporting period (28 April-22 May), and visibility was limited to only a few hours on many other days.

Small incandescent eruptions occurred after sunset on 3 May, the only incandescent activity seen during the reporting period. Fine ash fell in Antigua on 7 May, then after 2 days of weak steam emission (8-9 May) and a cloudy day (10 May), ashfall in Yepocapa, 8.5 km NW of the summit, was reported on the 11th and 12th. Ash rose to more than 1400 m early on 13 May and to about 1100 m the next day, when simultaneous activity from 3 vents was observed and several small directed blasts from a fourth vent sent hot avalanches down a canyon on the SE flank. Ash fell on Antigua each day between 15 and 20 May, but the volcano was visible only for brief periods; maximum observed ash cloud height was about 1500 m, at 0900 on the 18th. Only 1 earthquake was felt in Antigua during the report period, a small shock at 1145 on 5 May.

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: P. Newton, Antigua.