IG reported that on 9 April incandescent blocks ejected by Strombolian activity at Tungurahua rolled down the flanks as far as 3 km. An ash plume rose 3 km above the crater and drifted SW, W and NW. Minor ashfall was reported in Cahuaji, Choglontus (SW), and El Manzano (8 km SW). On 10 April an emission observed during a break in cloud cover rose 500 m and drifted W. Ash fell in Quero (20 km NW), Santa Anita, Calera, and El Manzano. Later that day a lava flow on the upper W flank, in the Mandur drainage, was estimated to be 2 km long, 100 m wide, and 15 m thick. On 11 April ash plumes drifted NW, and ashfall was reported in Quero and Tisaleo. The next day ash plumes rose 3 km and drifted W. Ejected blocks from Strombolian activity traveled 1 km down the flanks. A special bulletin released by IG on 14 April reported several small to moderate explosions. A significant explosion at 0831 produced an infrasound signal that was 150 decibels 5.5 km away. Unconfirmed reports indicated that windows in Chacauco and Cusúa shattered. The shock wave was also detected in other locations including Ambato and Riobamba. An ash plume rose 5 km. On 15 April plumes with low ash content rose 3 km and drifted W. Ash fell in Runtún and Mocha. A lahar descended the Achupashal drainage, causing a temporary halt to traffic traveling on the Baños- Penipe highway.

Geological Summary. Tungurahua, a steep-sided andesitic-dacitic stratovolcano that towers more than 3 km above its northern base, is one of Ecuador's most active volcanoes. Three major edifices have been sequentially constructed since the mid-Pleistocene over a basement of metamorphic rocks. Tungurahua II was built within the past 14,000 years following the collapse of the initial edifice. Tungurahua II collapsed about 3,000 years ago and produced a large debris-avalanche deposit to the west. The modern glacier-capped stratovolcano (Tungurahua III) was constructed within the landslide scarp. Historical eruptions have all originated from the summit crater, accompanied by strong explosions and sometimes by pyroclastic flows and lava flows that reached populated areas at the volcano's base. Prior to a long-term eruption beginning in 1999 that caused the temporary evacuation of the city of Baños at the foot of the volcano, the last major eruption had occurred from 1916 to 1918, although minor activity continued until 1925.

Source: Instituto Geofísico-Escuela Politécnica Nacional (IG-EPN)