Report on Tungurahua (Ecuador) — 29 May-4 June 2002
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 29 May-4 June 2002
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2002. Report on Tungurahua (Ecuador). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 29 May-4 June 2002. Smithsonian Institution and US Geological Survey.
1.467°S, 78.442°W; summit elev. 5023 m
All times are local (unless otherwise noted)
According to IRD, during 27 May-3 June nearly continuous gas, vapor, and ash emissions at Tungurahua sent plumes 1.5-2.5 km above the crater and deposited ash on the volcano's flanks. During the night of 29 May, low-intensity Strombolian activity was observed. After 30 May, more intense ash-rich emissions occurred. On the morning of 2 June a 0.5 mm uncompacted ash layer was deposited at the western base of the volcano. During the week, there was an abrupt increase in the number of daily explosions, which gradually decreased. Also, several explosions were observed sending ash plumes to 3-4 km above the crater and incandescent ballistic blocks as far as 2 km from the vent. According to IG, heavy rainfall generated a small lahar on 3 June that traveled NW. On the same day at 1321 a long-period earthquake was associated with an eruption that sent an ash cloud to a height of 2 km above the volcano. Ash fell to the NW.
Geologic Background. 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 itself collapsed about 3000 years ago and produced a large debris-avalanche deposit and a horseshoe-shaped caldera open to the west, inside which the modern glacier-capped stratovolcano (Tungurahua III) was constructed. 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.