Intermittent ash emission continued through late August, but no new lava flows were reported. The maximum observed ash cloud height was about 1,650 m, on 18 August. Summit glow and ejections of incandescent material were often visible at night.

Numerous hot avalanches moved down the NE, E, and SE flanks during the late afternoon and evening of 24 July. Small incandescent ejections were seen the next night and dark gray ash rose to 1,100 m the morning of the 26th. Activity had declined by that evening, and was characterized through the end of July by the emission of small, dense, brown to black ash puffs. Occasional jets of incandescent material from the main crater and fumarolic activity from a vent near the main crater were seen 29 July.

Activity declined further in early August. Very weak black ash emission during the morning of 1 August was succeeded by steaming that continued intermittently through the next day. Ash emission resumed 3 August and jets of incandescent ejecta were seen at night. Ash clouds rose about 800 m on 4 August; each ejection lasted 3-4 minutes followed by about 30 minutes of quiescence. Clouds obscured the volcano 5-9 August.

A series of loud rumbling sounds was heard in Antigua during the late afternoon and evening of 9 August. Another rumble was heard early 10 August, accompanying the ejection of an 1,100-m black ash cloud. Intermittent ejection of black ash continued for the next several days. Clouds rose to 1,200 m on the 12th and 1,600 m on the 13th, and a small earthquake was felt in Antigua at 2214 on 12 August. Incandescent ejecta were seen after sunset on 10, 11, 13, 14, and 15 August. A hot avalanche traveled about 600 m down the E flank on 17 August.

Immediately after a magnitude 5.4 earthquake at 0936 on 18 August, 51 km W of Fuego, ash emission became more voluminous. That evening ash clouds reached about 1,650 m above the summit. Early on 19 August, ash rose 1,100 m above the summit and a hot avalanche moved about 550 m down the SE flank late in the afternoon. Incandescent material was occasionally seen during the evenings of 19-21 August, but clouds prevented daylight observations. Activity weakened 22-23 August (the last days of observations reported here), with weak steaming and ash emission from several summit area vents.

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.