Intermittent activity continued through late January culminating in the largest eruption since 1974. The 29 December-28 January information is from Paul Newton, and the 29 January-1 February information was reported by Samuel Bonis to Richard Stoiber.

29 December-15 January: Black (primarily) to gray ash clouds were emitted at low velocity from at least 3 vents within the summit crater. Ash fell mainly on the upper N flank, but some fine material fell several kilometers downwind. Incandescent ejecta was visible above the summit on 30 December, and l, 5, 7, 9, and 15 January. Incandescent activity was weak except on the 15th, when bombs were ejected and ash fell on the E flank. Weak steaming from a small vent on the upper E flank was observed on 9 January. 16-17 January: Mostly steaming, with a little black ash emission. 18-22 January: Low-velocity black ash emission to a maximum height of about 370 m above the crater. 23-28 January: Activity decreased markedly to weak steam emission.

Weak earthquakes, accompanied by rumbling, were felt at 2015 on 29 December, 2130 and 2200 on 5 January, between 1100 and 1115 on 9 January (2 events), 1100 and 1215 on 15 January (lasting about 4 seconds each), and 0600 on 20 January (followed by black ash emission). Larger events were felt on 19 January at 2015 (15 seconds) and 2320 (about 4 seconds).

"Fuego had its strongest eruption since 1974 from 29-31 January. The eruption column reached about 4000 m above the crater, and 1 mm of ash blanketed the ground 5 km SW of the vent. Small nuées ardentes flowed down the canyon of the Rio Taniluya, on the SW flank of the volcano. Fuego was inactive at sunrise on 1 February."

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; R. Stoiber, Dartmouth College.