Ongoing volcanism, including ash explosions, pyroclastic flows, avalanches, and lahars had continued through November 2007 at Santa Maria (BGVN 32:10). Subsequent activity has been closely monitored by the Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH), with input from the Washington Volcanic Ash Advisory Center (VAAC).

Activity during 2008. On 11 January 2008, INSIVUMEH reported constant avalanches of blocks from the lava flows on the W and SW flanks of Santa María's Santiaguito lava dome complex. Weak-to-moderate explosions produced ash plumes that rose to altitudes of 4.1-4.5 km and drifted SW. On 6 February, weak explosions generated white columns of water and steam and ash that rose ~ 200 m above the crater rim. There were also a few avalanches onto the W flank lava flow. Degassing on 8 February was characterized by steam and gray plumes of fine ash on the SW flank. A significant magmatic explosion that threw fine ash up to ~ 5 km altitude and drifted ~ 4 km to the SW was followed by weak explosions of steam and ash. Avalanches of blocks from the crater rim on 12 February reached the lava flows on the S and SW flanks. Two moderate explosions expelled gray ash up to ~ 4 km altitude that dispersed to the SW.

The Washington VAAC (based on satellite imagery) reported that ash "puffs" from the Santiaguito lava dome complex rose ~ 4.5 km and drifted SW on 1 April, and then rose ~ 4 km and drifted W on 2 April. During 3-7 April, small explosions produced ash plumes; ashfall was reported in surrounding areas. This was followed on 15 April by three explosions expelling ash 300-900 m above the volcano and dispersing 5 km to the SW. Constant avalanches occurred to the W and SW. On 18 April another volcanic ash emission was reported by the Washington VAAC which rose to ~ 4.8 km, drifted SW, and extended ~ 30 km. More weak to moderate explosions occurred on 21 April which expelled gray ash clouds 300-800 m above the crater rim that drifted E. This activity was repeated on 25 April; the Washington VAAC reported an ash emission which rose to ~ 4.8 km and drifted ~ 13 km SW. On 28 April explosions sent ash plumes to an altitude of 4.1 km that drifted W.

Based on observations of satellite imagery, the Washington VAAC reported that ash puffs from the Santiaguito complex drifted NW on 13 May. On 22 May, two explosions were heard and gray ash emissions rose ~ 300-600 m above the crater rim and drifted S and SW, depositing ash in the Palajunoj area. Avalanches of blocks on the SW flanks were seen and heard. A lahar descended the Nima I River to the S on 25 May.

On 3 June, a Special Bulletin was issued to warn of the potential high water conditions in the Nimá I, Nimá II, San Isidro, Drum, Samala, rivers as a result of heavy rains in the area. On 5 June, avalanches were heard on the flanks of the volcano and overflows into the Samal and Mulu Rivers were reported. A lahar on 9 June about 15 m wide and up to 2 m deep descended the Nima I River, carrying blocks up to 1 m in diameter, and smelling of sulfur.

During the morning of 19 June, six weak-to-moderate explosions produced ash plumes that rose to altitudes of 2.8-3.3 km and drifted SW and S. An incandescent lava flow accompanied by constant avalanches of blocks descended the SW flank. On 20 June, five weak-to-moderate explosions expelled gray ash up to ~ 600-800 m above the crater, spreading to the SW over the area of Palajunoj. The lava flow to the SW continued and incandescent lava could be seen at night, accompanied by constant avalanches of blocks and fine ash. A lahar traveled S down the Nima I river, carrying blocks up to 1 m in diameter. These conditions continued through 24 June.

On 4 July, an explosion produced an ash plume that rose to an altitude of 3.3 km and drifted SW. A lahar traveled S down the Nima I River, carrying tree limbs and blocks up to 50 cm in diameter. On 7-8 July, sounds resembling avalanches descending the flanks were reported; visual observations were hindered due to cloud cover. On 22 July seismic stations detected a lahar in the Nima I river. Explosions observed on 23, 28, and 29 July from the Caliente cone produced ash plumes that rose to altitudes of 2.8-3.3 km and drifted SW and W. Ashfall was reported in areas downwind. A lava flow and avalanches of blocks descended the SW flank. On 28 July, weak pyroclastic flows also traveled down the SW flank.

During 21-26 August, explosions from the Caliente cone, part of the Santiaguito complex, produced ash plumes that rose to altitudes of 2.8-3.3 km and drifted S, SW, and W. Constant degassing from the crater was noted.

On 10 September seismic stations detected a lahar in the Nima I River. The lahar, about 18 m wide and up to 2 m deep, carried blocks and smelled of sulfur. During 11-16 September, explosions produced ash plumes that rose to altitudes of 2.8-3.3 km and drifted SW; on 18 September, the Washington VAAC reported that an ash plume rose to an altitude of 4.3 km and drifted SSW. On 24 September explosions produced ash plumes that rose to altitudes of 2.8 km and drifted SW. Avalanches of material from lava flows descended the SW flank.

On 11 and 15 November, the Washington VAAC reported that ash puffs drifted SW. On 12 December, explosions from the Caliente dome produced an ash plume that rose to an altitude of 3.2 km and drifted SW; the Washington VAAC reported a plume to an altitude of 5.8 km. On 16 December, two ash puffs drifted W and WNW at altitudes of 4.3-4.6 km. The Washington VAAC again reported that during 17-20 and 22 December ash plumes drifted SW, W, and NW; plumes rose to an altitude of 5.8 km. On 22 December, white plumes drifted SW and avalanches occurred from the crater rim. On 23 December a small ash plume drifted NW and explosions resulted in pyroclastic flows. Ash plumes rose to an altitude of 3.3 km and drifted S and SW. On 25 December a puff of ash drifted WNW.

Activity during 2009. Activity continued into 2009 and the Washington VAAC reported that two small ash plumes drifted ESE on 1 January. During 4-5 January, gas and steam plumes possibly containing some ash drifted SW and WSW. On 5 and 6 January fumarolic plumes drifted 100 m above the crater. Five explosions produced ash plumes that rose to altitudes of 2.8-3 km and drifted W and SE. A few avalanches originating from a lava flow descended the W flank. Explosions during 30 January-3 February produced plumes that rose to altitudes of 2.6-3.2 km and drifted W, SW, and S. Avalanches that were periodically incandescent descended the S and W flanks of Caliente lava dome.

The Washington VAAC reported that on 4 February multiple ash puffs drifted W. Explosions on 6 February produced plumes that rose to altitudes of 2.8-3.1 km and also drifted SW. Ashfall was reported in areas downwind. Ash puffs on 12 February drifted WSW and W. On 16-17 February, explosions produced ash plumes that rose to altitudes of 2.7-3.3 km and drifted SW. Small pyroclastic flows on 16 February descended the SE flank and reached the Nima I River. Incandescent avalanches were noted on 17 February and fumarolic plumes drifted SW.

On 18 February, a dense ash plume drifted W, and on the 20th an explosion sent an ash plume to an altitude of 3.2 km that drifted E. On 24 February, an explosion produced a white plume that rose 500 m above the summit and drifted SW. Incandescence was seen SW of Caliente dome. On 26-27 February and 2 March, explosions produced ash plumes that rose to altitudes of 2.8-3.4 km and drifted SW. Ashfall was reported in nearby areas. Avalanches were seen SW of the Caliente dome.

Based on satellite imagery, the Washington VAAC reported that during 4-6 March ash plumes drifted W. On 6 and 10 March, ash plumes rose to 2.8-3.4 km and drifted SW, NW, and N. Ashfall was reported in areas downwind. On 12, 16, and 17 March, explosions produced ash plumes that rose to altitudes of 2.7-3.5 km and drifted E and SW. A few avalanches originated from an active lava flow and traveled down the SW flank. On 12 March an ash plume drifted S, and on 15 March, an ash plume rose to an altitude of 3 km and drifted SW and WSW.

During 24-28 April explosions produced ash plumes that drifted 5-8 km WSW, although the number of explosions had decreased during the previous few weeks. On 5, 8, and 9 June ash plumes rose to altitudes of 2.8-3.3 km and drifted SW. Gas plumes that were sometimes gray rose ~ 300-600 m above the Caliente dome, and avalanches descended the S and W flanks. On 26 and 29 June explosions produced ash plumes that rose to altitudes of 2.9-3.3 km and drifted W and SW.

On 26 June, the seismic network detected a lahar that traveled S down the Nima I River. Steam plumes and a sulfur odor rose from the deposits. The lahar was 15 m wide and 1 m thick at the toe, and carried blocks up to 1.5 m in diameter. On 2 July lahars descended both the Nimá I and Nimá II rivers, carrying tree branches and blocks 50-75 cm in diameter. The lahars were 15 and 20 m wide.

On 6 July, explosions produced ash plumes that rose to altitudes of 2.8-3.2 km and drifted W. On 31 July and 3 August, explosions produced ash plumes, and the Caliente lava dome was incandescent. On 3 August, ash plumes rose to an altitude of 3.1 km and drifted W. Fumarolic plumes rose 200 m above the dome and rumbling noises were occasionally heard.

On 28 August, another explosion was noted. On 1 September, fumarolic plumes rose 150 m above Caliente dome and drifted SW and avalanches descended the SW flank of the dome. On 14 September an explosion produced an ash plume that rose to an altitude of 3.3 km. The plume drifted SW and caused ashfall. Avalanches went to the SW.

The Washington VAAC reported that on 22 October multiple ash plumes drifted less than 20 km SW. On 23 and 26 October, explosions produced ash plumes that rose above Caliente dome to altitudes of 3-3.3 km. The plumes drifted W and SE and caused ashfall. Avalanches descended the SW flank of the dome. Degassing sounds resembling airplane engines were also heard.

On 6 November, an explosion produced a plume that rose 900 m and drifted SW. The Washington VAAC reported that on 8 November a small gas plume possibly containing ash drifted less than 10 km SSW. Another small plume was seen later that day. On 13 November, a plume drifted SW. Avalanches descended the SW flank of the dome and the Washington VAAC reported that on 16 November multiple ash plumes drifted WSW.

On 20 November, two explosions produced an ash plume that drifted SW. Avalanches descended the SW flank of the dome. An explosion on 24 November produced an ash plume the rose to an altitude of 3.3 km and drifted SE. Ashfall was reported in areas downwind.

On 11, 14, and 15 December, explosions produced ash plumes that rose to altitudes of 2.8-3.5 km and drifted W and SW. Avalanches occasionally descended the SE flank of the dome. On 15 December, explosions generated pyroclastic flows that descended the E and SW flanks. On 30 December explosions produced ash plumes that rose to altitudes of 3-3.4 km and drifted W and SW. The Washington VAAC reported that ash plumes seen on satellite imagery drifted more than 30 km WSW. Avalanches occasionally descended the SW flank of the dome.

Activity during January-April 2010. Incandescent avalanches traveled down the SW flanks on 8 January 2010. A few explosions on 5 and 11-12 January produced ash plumes that rose to altitudes of 3.1-3.4 km and drifted S, SE, and SW. Avalanches from a lava flow descended the W flank of the dome. On 21 January ashfall was reported in areas near the Santiaguito complex. The next day an explosion produced an ash plume that rose to an altitude of 3.2 km and drifted SW. An ash plume seen on satellite imagery drifted less than 10 km.

On 2 and 4 March, explosions produced ash plumes that rose to altitudes of 2.7-3.1 km and drifted E and NE. Ash fell in areas downwind. Ash fell in inhabited areas downwind. The Washington VAAC reported that on 8 March an ash plume was seen in satellite imagery drifting WNW. On 29 March, explosions produced ash plumes that rose to altitudes of 3-3.3 km and drifted W over inhabited areas. Avalanches from a lava flow descended the SW flank. On 30 March a diffuse ash plume was seen in satellite imagery.

On 20 April, explosions produced ash plumes that rose to altitudes of 2.8-3.4 km and drifted S and SE. On 26 April, ash explosions and pyroclastic flows generated ash plumes that rose to an altitude of 8.3 km and drifted NW and N. Ashfall was reported in Quetzaltenango (18 km WNW) and other areas to the W, NW, and N. According to news articles, schools in 10 communities were closed and flights were banned within a 20-km-radius of the volcano.

Geological Summary. Symmetrical, forest-covered Santa María volcano is part of a chain of large stratovolcanoes that rise above the Pacific coastal plain of Guatemala. The sharp-topped, conical profile is cut on the SW flank by a 1.5-km-wide crater. The oval-shaped crater extends from just below the summit to the lower flank, and was formed during a catastrophic eruption in 1902. The renowned Plinian eruption of 1902 that devastated much of SW Guatemala followed a long repose period after construction of the large basaltic-andesite stratovolcano. The massive 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 vents, with activity progressing E towards the most recent, Caliente. Dome growth has been accompanied by almost continuous minor explosions, with periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.

Information Contacts: Instituto Nacional de Sismologia, Vulcanología, Meteorología, e Hidrologia (INSIVUMEH), Unit of Volcanology, Geologic Department of Investigation and Services, 7a Av. 14-57, Zona 13, Guatemala City, Guatemala (URL: http://www.insivumeh.gob.gt/); Washington Volcanic Ash Advisory Center, Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: http://www.ospo.noaa.gov/Products/atmosphere/vaac/); Coordinadora Nacional para la Reducción de Desastres (CONRED), Av. Hincapié; 21-72, Zona 13, Guatemala City, Guatemala (URL: http://www.conred.org/).