Activity at Fuego remained intermittent and relatively weak during most of the 25 May-27 June reporting period, although vigorous ejection of incandescent tephra occurred on 20 June. Rainy season clouds often made observation of the volcano impossible, particularly in early June.

During periods of visibility between 25 and 30 May, Fuego's activity was usually confined to mild steaming from the summit. However, voluminous black ejecta rose about 3/4 km early on 25 May and about 0.5 km in the late afternoon of 30 May, the latter followed by a light ashfall on Antigua. On 2 June at 1615, a brown tephra cloud was ejected at high velocity to 2.5-3 km above the summit. The volcano was briefly visible late the next afternoon, but no activity was taking place.

Except for a 30-minute period on 7 June (when it was inactive) Fuego was obscured by clouds 4-11 June. Weak vapor emission was glimpsed through clouds on 12, 13, and 15 June. Ash ejection was seen twice between the 16th and 19th, to 0.3 km height early 16 June and to about 0.5 km 24 hours later, but the volcano was otherwise inactive.

On 20 June, weak emission of light brown ash to 400 m height was followed at 0930 by ejection of incandescent tephra to more than 0.8 km above the summit. Large yellow, orange, and red blocks fell on the flanks before clouds prevented further observations at 1030. Intermittent voluminous ash emission could be seen for the next four days, some originating from a vent W of the summit. Maximum cloud heights were about 0.7 km. When the volcano was next (briefly) visible, on 27 June, activity had declined to occasional steaming.

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.