Explosions and pyroclastic flows at Santa Maria volcano, Guatemala
High-level explosive activity at Santa María’s Santiaguito dome complex on May 6, 2025, produced ash plumes up to 900 m (2 950 feet) above the crater and pyroclastic flows down the southern and southwestern flanks.
The Instituto Nacional de Sismología, Vulcanología, Meteorología e Hidrología (INSIVUMEH) reports ongoing activity at the Santa Marias’ Caliente dome, characterized by white degassing columns reaching 500 m (1 640 feet) above the crater and weak-to-moderate explosions generating gas-and-ash plumes up to 800–900 m (2 620–2 950 feet) in height on May 7.
Plumes drifted southwest under cloudy atmospheric conditions with 6 mm (0.2 inches) of rainfall and northeasterly winds. Nighttime incandescence was visible within the crater, and collapse of accumulated volcanic material generated pyroclastic flows down the southern and southwestern flanks.
The Santiaguito Volcano Observatory (OVSAN) warned of the ongoing potential for partial dome collapse, either due to explosive activity or gravitational instability, which could produce long-range pyroclastic flows toward the south, southwest, and southeast sectors.
INSIVUMEH is noted that continued rainfall may generate lahars in various drainages surrounding the volcano.
During the reporting period from April 9 to 15, INSIVUMEH recorded frequent lava extrusion at the Caliente dome and daily explosive activity reaching up to seven explosions per hour. Resulting gas-and-ash plumes rose up to 1.2 km (3 940 feet) and dispersed as far as 40 km (25 miles) to the south, east, southeast, and northeast.
Effusive activity contributed to blocky lava flows and repeated dome collapse events that triggered block avalanches, predominantly down the southern, southwestern, and western flanks. Some collapses generated short pyroclastic flows on all flanks.
Heavy rainfall on April 9 produced lahars in the Tambor drainage (south-southwest), transporting meter-sized blocks, fine sediments, tree trunks, and branches. Ashfall was reported in several communities between April 11 and 13, including Nuevo Palmar (12 km / 7.5 miles SSW), Pueblo Nuevo to San Felipe (15 km / 9.3 miles SSW), Loma Linda (7 km / 4.3 miles W), Las Marías (9.5 km / 5.9 miles S), Calaguaché (9 km / 5.6 miles S), and Belén (10 km / 6.2 miles S).
References:
1 Daily Volcanology Bulletin – INSIVUMEH – May 7, 2025
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