Steam and ash emission has continued intermittently through late October. A substantial increase in activity 19-20 October was reported. Columns of dark gray ash were ejected at about 1-hour intervals on 24 September, accompanied by rumbling. Activity declined the next day but similar ash ejections resumed on 26 September, lasting until evening. At 2000, loud rumbling was succeeded by a small eruption of incandescent ash and bombs, accompanied by hot avalanches that moved a short distance down canyons on the upper flanks. Persons near the volcano felt an earthquake 2 hours after the eruption and several more the next day. Incandescent ash was ejected on 28 September until 2200 and thick ash, accompanied by loud explosions, was emitted for several hours the next day. A moderate ash eruption, including small hot avalanches, was visible through thick cloud cover on 2 October. Two days later, several explosions at around 1630 produced black ash clouds. About 3-4 brown to black ash puffs per hour were reported on 7 October, accompanied by a red glow at night. Incandescence was also reported during the night of 9 October.

Explosions increased markedly on 19 October, producing minor local ashfalls from clouds that rose 1,500 m above the vent, and continuous small hot avalanches, which were again restricted to canyons on Fuego's upper slopes. Maximum activity was on 20 October, when a trace of ash fell on villages SW of the vent. Intermittent small steam, ash, and ash flow eruptions continued on a reduced scale as of 26 October.

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: S. Bonis, IGN; R. Stoiber, Dartmouth College.