According to the Smithsonian / USGS Weekly Volcanic Activity Report, during 28-29 April explosions from Santa María's Santiaguito lava dome complex in Guatemala, produced ash plumes that rose 600-800m above the crater and drifted S, SW, and W. Block avalanches descended the flanks of Caliente dome. At night pyroclastic flows traveled down the Rio Nima I and Rio Nima II drainages.
Guatemalan departments of Quetzaltenango and Retalhuleu were declared this Friday in yellow alert due to the increased activity of the volcano Santiaguito. According to the National Institute for Seismology, Vulcanology, Meteorology and Hydrology of Guatemala (Insivumeh), the increase is manifested in the number of explosions per hour. Such explosions generate weak and moderate echoes, that could be heard 10 kilometers away, and constant avalanches of rocks in the southwestern and eastern sides of the volcano. The Insivumeh uninterruptedly monitors the volcano and advises the Directorate General of Civil Aviation to take precautions with air traffic in a radius of 15 kilometers due to the ash emissions. - Inside Costa Rica.The Smithsonian / USGS Weekly Volcanic Activity Report provides the following geologic summary for the volcano: Symmetrical, forest-covered Santa María volcano is one of a chain of large stratovolcanoes that rises dramatically above the Pacific coastal plain of Guatemala. The stratovolcano has a sharp-topped, conical profile that is cut on the SW flank by a large, 1-km-wide crater, which formed during a catastrophic eruption in 1902 and extends from just below the summit to the lower flank. The renowned Plinian eruption of 1902 followed a long repose period and devastated much of SW Guatemala. The large dacitic Santiaguito lava-dome complex has been growing at the base of the 1902 crater since 1922. Compound dome growth at Santiaguito has occurred episodically from four westward-younging vents, accompanied by almost continuous minor explosions and periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.