INSIVUMEH and CONRED reported that on 20 October hot lahars descended Fuego’s Las Lajas (SE) and Mineral drainages, carrying blocks up to 2 m in diameter along with branches and tree trunks. The lahars were 20-30 m wide and 2 m deep. During 20-23 October there were 8-15 weak explosions recorded per hour, producing gray ash plumes that rose 750-850 m above the crater rim and drifted 12 km W and SW. Ashfall was reported in areas downwind, including Morelia (9 km SW), Santa Sofia (12 km SW), Sangre de Cristo (8 km WSW), Finca Palo Verde, Panimaché (8 km SW), and San Pedro Yepocapa (8 km NW). Lava fountains rose 100-200 m high. Avalanches of blocks descended the El Jute (SE), Ceniza (SSW), and Las Lajas (SE) drainages, with material reaching vegetated areas.

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)