Based on INSIVUMEH special bulletins, CONRED reported increased activity at Fuego on 4 August, characterized by explosions ejecting incandescent material as high as 300 m above the crater rim and lava traveling 600 m down the Ceniza (SSW) ravine. Explosions generated ash plumes that rose almost 1 km and drifted 12 km W and SW. INSIVUMEH reported that multiple explosions during 5-6 August generated ash plumes that rose as high as 850 m above the crater and drifted 10 km W. Some explosions generated shock waves that rattled nearby structures. Incandescent material was ejected 100 m above the crater rim, and caused avalanches of material that traveled down the Ceniza, Taniluyá (SW), Santa Teresa (W), Las Lajas (SE), Honda (E), and Trinidad (S) drainages. Ash fell in areas downwind, including Sangre de Cristo (8 km WSW) and Yepocapa (8 km WNW). A lava flow was active 600 m down the Ceniza drainage. Explosive activity increased on 7 August. Ash plumes rose as high as 750 m and drifted 10 km W and SW. Ballistics were ejected more than 150 m above the crater and fell 200 m away. Shock waves continued to vibrate houses in nearby communities. During 7-8 August two lava fountains rose 150 m high, heralding the seventh effusive episode at Fuego in 2017. The fountains fed lava flows, 1.5 km and 700 m long, in the Ceniza and the Santa Teresa ravines, respectively. Explosions (occurring at a rate of 6-8 per hour) produced ash plumes that drifted 20 km W, causing ashfall in Panimache (8 km SW), Morelia (9 km SW), Santa Sofía (12 km SW), El Porvenir (8 km ENE), and Yepocapa.

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)