The Instituto Nacional de Sismología, Vulcanologia, Meteorologia e Hidrología (INSIVUMEH) reported that eruptive activity at Fuego continued during 23-30 September. Daily Strombolian explosions were recorded by the seismic network at rates of 5-10 per hour. The explosions generated daily gas-and-ash plumes that rose as high as 1.1 km above the summit and drifted as far as 40 km NW, W, and SW. Occasional rumbling sounds, shock waves, and/or sound associated with gas emissions were reported; the shock waves rattled buildings and structures in communities on the SW and W flanks during 23-24 September. Explosions ejected incandescent material 100-200 m above the summit during 27-30 September, sometimes showering the upper flanks with incandescent material. Daily block avalanches descended the flanks, including the Las Lajas (SE), Seca (W), Taniluya (SSW), Trinidad (SSW), Santa Teresa (W), and Ceniza (SSW) drainages, occasionally reaching vegetated areas. Ashfall was reported in areas downwind including Finca Palo Verde (10 km WSW), Yepocapa (12 km SW), Sangre de Cristo (8 km W), El Porvenir (11 km SW), Quisaché (8 km NW), and Soledad (11 km N) during 23-24 September, in Yepocapa during 24-25 September, in areas on the SW flank during 25-26 September, and in Panimache (8 km SW), Sangre de Cristo, Finca Palo Verde, and Yepocapa during 28-29 September.

Heavy rain generated lahars in multiple drainages during 22-23, 25, and 28 September. Special reports issued at 1655, at 1707, at 1736, and 1813 on 22 September noted that lahars descended the El Jute (ESE), Las Lajas, Ceniza, Zarco, Mazate, Seca, and Mineral (W) drainages. The lahars that descended the El Jute and Las Lajas drainages were hot and had a sulfur odor. On 23 September lahars descended the Santa Teresa, El Jute, Ceniza, and possibly the Las Lajas based on reports from 1410, 1440, and 1500. Reports issued at 1530 and 1601 on 25 September noted that lahars traveled down the Seca, Mineral, Ceniza, Zarco, and Mazate drainages. Lahars descended the Ceniza, Zarco, and Mazate drainages the next day based on a report from 1940 on 28 September. All of the lahars were characterized as a mixture of water and sediment that carried tree branches, trunks, and blocks 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)