The Instituto Nacional de Sismología, Vulcanologia, Meteorologia e Hidrología (INSIVUMEH) reported that eruptive activity at Fuego continued during 16-23 September. Daily Strombolian explosions were recorded by the seismic network at rates of 5-12 per hour. The explosions generated daily gas-and-ash plumes that rose as high as 1.1 km above the summit and drifted 10-30 km in multiple directions. Occasional rumbling sounds, shock waves, and/or sound associated with gas emissions were reported. Explosions ejected incandescent material 100-200 m above the summit during 16-17 and 21-22 September and showered the upper flanks with incandescent material during 21-22 September. Block avalanches descended the flanks, including the Las Lajas (SE), Seca (W), Taniluya (SSW), Trinidad (SSW), Santa Teresa (W), and Ceniza (SSW) drainages, sometimes reaching vegetated areas. Occasional ashfall was reported in areas downwind including Panimache I and II (8 km SW), Morelia (9 km SW), and Santa Sofía (12 km SW) and local areas to the NE.

Heavy rain generated lahars in multiple drainages during 17-19 September. Lahars descended the Ceniza, Zarco, and Mazate drainages based on a special report issued 1359 on 17 September, and the Seca and Mineral drainages based on a report issued at 1659 that same day. Special reports issued at 1430, 1445, and 1523 on 18 September noted that lahars descended the El Jute (ESE), Las Lajas, Ceniza, Zarco, Mazate, Seca, and Mineral (W) drainages. In the early afternoon on 19 September lahars descended the El Jute and Las Lajas drainages and the Ceniza, Zarco, and Mazate drainages based on reports issued at 1455 and 1505, respectively. Later that day hot lahars with a sulfur odor descended the El Jute and Las Lajas drainages, based on a report issued at 2010. All of the lahars were characterized as a mixture of water and sediment that carried tree branches, trunks, and blocks possibly as large as 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 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)