Fuego was previously discussed in BGVN 30:08. This report discusses ongoing developments at Fuego since July 2005 and through December 2006. In general, the volcano erupts vesicular, olivine-bearing basaltic lava flows. They traveled from the central crater hundreds of meters down the S, SW and W flanks, and the lava flow fronts released occasional blocky avalanches of incandescent material. The latter process is generally omitted from the rest of this report unless the avalanche(s) were particularly noteworthy, as in cases where pyroclastic flows were also noted.

On 17 July 2005, an ash plume ~ 3.5-4 km high accompanied small pyroclastic flows down Santa Teresa and Taniluyá ravines. This activity continued sporadically through October 2005.

From 2-7 November 2005, weak explosions and low ash plumes occurred along with lava flows that traveled down the volcano's S and SW flanks, extending 600 m towards the Taniluyá ravine, and 300 m towards the Cenizas ravine. On 14 November, two lava flows traveled from the S edge of the central crater 150 m toward the Cenizas ravine, and 400 m toward the Taniluyá ravine. A third lava flow traveled 600 m W towards the Santa Teresa ravine. Between 17 and 21 November, lava flows traveled S towards the Cenizas and Taniluyá ravines and W towards Santa Teresa ravine.

On 13 December 2005, two lava flows from Fuego extended 200-300 m W and SW of the central crater. On 27 December 2005 an ash plume rising ~ 7.6 km altitude extended SSW and SSE of the volcano; lava flows traveled ~ 2 km S down Taniluyá ravine, and W down Seca ravine, initially extending ~ 800 m and 1,200 m, respectively.

At 0602 on 27 December, a pyroclastic flow descended S. Ash fell S of the volcano in the port of San Jose. Later that day, lava flows extended 1.2 and 1.3 km, and pyroclastic flows descended 1.8 and 2 km down the Taniluyá and Seca ravines, respectively. Lava flows also traveled W toward Santa Teresa ravine, and SE towards the Jute and Lajas ravines. An ash plume rose ~ 7.6 km, and a small amount of ash fell W and SW of the volcano in the villages of Morelia, Santa Sofía, Los Tarros, and Panimaché (~ 7 km SSW). This activity continued through 29 December with more lava flows and bombs. The emissions hurled incandescent lava clots ~ 75 m high, spawned lava flows, and generated a dark plume rising to ~ 1 km above the crater rim.

January 2006 activity was essentially a continuation of December's with moderate-to-strong explosions and incandescent lava ejecta hurled ~ 40 m high. Explosions could be heard 25-30 km away. The explosions were accompanied by rumbling sounds and acoustic waves that shook windows and doors in villages near the volcano. Ash plumes rose ~ 1 km to ~ 1.5 km. On 22-23 January, there were Strombolian lava ejections rising ~ 100 m above the crater rim accompanied by block avalanches down the SW flank.

During February and March 2006, explosions moderated but activity continued. Weak-to-moderate explosions occurred; shock waves were sometimes felt in villages near the volcano. On 6-7 March, ash emissions up to ~ 4.6 km altitude were visible on satellite imagery.

From 22 through 28 March, Fuego ejected incandescent material up to ~ 50-75 m and gas plumes to ~ 300 m above the crater rim. Short pyroclastic flows from avalanches occurred on the upper flanks. On 28 March, pyroclastic flows traveled ~ 450 m S, and avalanches occurred from the lava-flow fronts.

On 17 April 2006, explosive ejections threw lava ~ 50-75 m above crater rim, and gas plumes rose to ~ 150-200 m. Lava flowed ~ 400 m S towards Taniluyá ravine.

During 17-18 May 2006 lava flows reached ~ 100 m SW towards the Taniluyá river and ~ 500 m SW towards the Cenizas river. Fumarolic gases rose to ~ 600 m above the crater rim and drifted E and W.

On 29 June 2006 fumarolic gases rose to ~ 125 m , spatter to tens of meters, and ash plumes ~ 2.2 km respectively above the crater rim. Lava flows extended ~ 400 m SW toward the Cenizas river. Pyroclastic flows traveled mainly SW along the Cenizas river, with a lesser number moving SW along the Taniluyá river.

On 3 July 2006, explosions discharged incandescent material hundreds of meters above the central crater and avalanches traveled ~ 300-500 m SW along the Cenizas river.

The only activity reported in August occurred on the 16-17th, when ash explosions reached 300-800 m above the crater rim, and explosions of incandescent material produced avalanches that descended 300-500 m SW towards the Cenizas, Taniluyá, and Santa Teresa river valleys.

The latter half of September 2006 continued the characteristic previous activity with explosions that sent incandescent lava 75-100 m above the crater rim and that generated hot avalanches SW towards the Taniluyá River.

On 15 November, lava flows traveled about 150 m SW, and avalanches occurred from the lava-flow fronts. On 17 November, three out of seven explosions propelled incandescent material 100 m above the central crater rim. Relative quiescence followed through December 2006.

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.

Information Contacts: Instituto Nacional de Sismologia, Vulcanología, Meteorología e Hidrologia (INSIVUMEH), Ministero de Communicaciones, Transporto, Obras Públicas y Vivienda, 7a. Av. 14-57, zona 13, Guatemala City 01013, Guatemala (URL: http://www.insivumeh.gob.gt/); Coordinadora Nacional para la Reducción de Desastres (CONRED), Av. Hincapié 21-72, Zona 13, Guatemala City, Guatemala; Washington Volcanic Ash Advisory Center (VAAC), 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/).