INSIVUMEH reported that in general 3-8 explosions per hour were recorded at Fuego during 26 September-3 October, though the rate was not determined on some of the days. The explosions generated ash-and-gas plumes that rose as high as 1.1 km above the crater rim and drifted as far as 30 km NW, W, and SW. Minor ashfall was reported in areas downwind including Morelia (9 km SW), Panimaché I and II (8 km SW), Santa Sofía (12 km SW), El Porvenir (8 km SE), Aldeas, and San Pedro Yepocapa (8 km NW). Rumbling was heard daily, and shock waves were occasionally detected. Explosions caused daily block avalanches to descend various drainages including the Ceniza (SSW), Seca (W), Trinidad (S), Taniluyá (SW), Honda (E), and El Jute (ESE), and Las Lajas (SE). The explosions ejected incandescent material as high as 300 m above the summit on most days. In the early afternoon on 27 September lahars descended the Mineral and Seca drainages, carrying tree branches, trunks, and blocks as large as 1 m in diameter. In the early evening on that same day lahars descended the Las Lajas and Jute drainages, carrying tree branches, trunks, and blocks as large as 1.5 m in diameter. In the afternoon of 29 September a hot lahar traveled down the Ceniza, carrying blocks as large as 1.5 m as well as tree trunks and branches. On 30 September a lahar in the Ceniza transported trunks and branches and blocks up to 3 m in diameter.

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.

Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH)