Emission of black to gray ash continued through March. Cloudy weather prevented observations on 9 days during March, and no report on the lava flows was available. Intermittent incandescence was seen during the evening of 26 February, but no incandescence has been observed since then. Activity was limited to weak steaming on 28 February and 22, 25, 27, and 29 March.

Strong activity occurred on 25 February, and 2, 4, 23, and 30 March. Ash columns rose about 1000 m above the summit at 1700 on 25 February, and from 0600 until clouds obscured the volcano at 1100 on 2 March. On 4 March, black ash was emitted to 1250 m above the vent for over 3 hours, beginning at 0600, but the column had become lighter colored by 1100 when clouds prevented further observation. Between 0730 and 1030 on 23 March, fine ash and vapor reached 1800 m above the vent, while heavy ashfall occurred on the upper N flank. At 0600 on 30 March, emission of black ash from the main crater was accompanied by a vapor plume from the N vent. Shortly before 0800, a 2300-m black column was emitted, appearing to originate from both vents, and a hot avalanche flowed down a canyon on the E flank. The eruption could be seen above the clouds until 1100, when visibility became completely obscured.

Earthquakes were felt in Antigua, 17 km NE of Fuego, on 4 March at 0550 (moderately strong) and 1137 (weaker); 13 March at 0130 (weak); 22 March at 0340 (weak); and 30 March at 1330 (strong, lasting 4 seconds).

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.