A column of incandescent ejecta was seen above the summit after sunset on 22 May, but observed activity declined between 23 and 28 May to emission of steam and ash plumes (usually gray to dark gray) reaching a maximum height of 900 m. Ash fell on Antigua on 29 May, but clouds limited observation until evening. During the night of 29-30 May a red glow was seen over the summit, accompanied by occasional incandescent eruptions. Glowing avalanches flowed down canyons on the NE and SE flanks. After sunrise on the 30th, black ash could be seen discoloring a cloud bank 1,000 m above the summit before visibility was totally obscured at midmorning. Activity the next day was weak and no incandescence was observed.

The following information is from Samuel Bonis, David Harlow, and Keith Priestly (see 3:7 for 1-14 June observations). Fuego's eruption intensified on 15 June. Two viscous flows were extruded from the summit area and traveled slowly down canyons on the E and SE flanks, accompanied by vigorous ash ejection. This activity continued the next day, accompanied by almost constant rumbling. The ash cloud rose an estimated 3 km on the 16th and was seen by airline pilots from as far away as the Mexican border, about 170 km NW. At Yepocapa, 1-2 mm of ash fell in about 1.5 hours. By 17 June, lava extrusions had ended, and explosive activity was confined to weak ash emission, which was continuing on 19 June.

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; S. Bonis, IGN; D. Harlow, USGS, Menlo Park, CA; K. Priestly, Univ. of Nevada, Reno.