On 25 May, CONRED reported that the Alert Level for Fuego was lowered from Yellow to Green based on recent communication with nearby communities and monitoring by scientists at INSIVUMEH. During 28-29 May, INSIVUMEH reported that the lava flow on the S flank continued to advance and produce incandescent blocks that rolled W into the Taniluyá River valley. Low rumbling noises were heard during 26-27 May and occasionally accompanied pyroclastic explosions. Additional explosions produced plumes to an altitude of 4.1 km (13,500 ft) a.s.l. and expelled incandescent material about 100 m above the crater. Avalanches of blocks were observed on the S and SW flank. Gray plumes drifted S. Steam-and-gas plumes rose to an altitude of 4.6 km (15,100 ft) a.s.l.

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.

Sources: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH), Coordinadora Nacional para la Reducción de Desastres (CONRED)