On 6 February, IG reported that since 3 February Tungurahua had produced almost constant emissions of gas, steam, and ash that rose 3-4 km above the crater and drifted N, causing ashfall in Ambato (31 km N), Patate (NW), Latacunga, and parts of Quito (130 km N). During 5-6 February ash plumes drifted E and SE and caused ashfall in Pondoa (8 km N), Vazcún (N), Runtún (6 km NNE), and San Antonio, and to a lesser extent in Rio Verde and Rio Negro. Strombolian activity was observed on 6 February.

Cloud cover often prevented visual observations during 7-11 February; explosions continued to be detected, roaring was periodically heard, and sounds resembling rolling blocks were occasionally reported. On 7 February ash fell in Palictahua. The next day a gas-and-ash plume rose 500 m and drifted W and SW. On 9 February an ash plume rose 4 km and drifted NW and NE. Strombolian activity ejected blocks 1 km away. During 10-11 February explosions vibrated structures, and ashfall was reported in Quero (20 km NW), Mocha (25 km WNW), El Manzano (8 km SW), and Choglontus (SW).

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)