Cloudy weather continued to hamper observations through December, but black ash emission was frequently visible during the day and glow or small incandescent eruptions at night.

Brief, intermittent ejection of black ash occurred 20 November and was occasionally visible through clouds 24-28 November. Weak glow during the night of 20 November brightened the next night and was weak again on 22 November. Felt earthquakes on 23 November preceded incandescent tephra ejection during the night.

On 29 November, activity had declined to steaming within the crater without night glow, which persisted until the afternoon of 2 December, when felt earthquakes preceded black ash ejection. Intermittent, 5-minute incandescent eruptions were seen that night and more ash was ejected the next morning. Glow was seen on 6 December and weak black ash emission was occasionally visible through the 9th.

Visibility was poor during the next 10 days. Black ash was seen on 12 and 14 December, but the volcano was only steaming on the 17th. A glow was observed on 18 December and intermittent black ash puffs were seen during the next 3 days. Ash clouds rose more than 650 m above the crater during the mornings of 22 and 23 December, but activity had weakened by the afternoon of the 23rd. On 24 December, 200-m ash clouds were emitted in the afternoon and there was a glow in the crater at night. The next day, intermittent ash puffs reached 600 m above the crater and incandescent eruptions, accompanied by a small glowing avalanche, occurred at night. Ash puffs continued through 28 December, and small incandescent eruptions were seen that night.

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.