Report on Tungurahua (Ecuador) — 5 March-11 March 2003
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
5 March-11 March 2003
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2003. Report on Tungurahua (Ecuador). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 5 March-11 March 2003. Smithsonian Institution and US Geological Survey.
1.467°S, 78.442°W; summit elev. 5023 m
All times are local (unless otherwise noted)
On 5 March at 1539 lahars began to descend the gorges on Tungurahua's W flank, obstructing the route between the towns of Baños and Pelileo. Around 7 March volcanic and seismic activity intensified at Tungurahua and according to the Washington VAAC, IG reported that ash from an explosion rose to ~7 km a.s.l. and drifted SW. No ash was visible on satellite imagery. IG also reported that by 9 March several low-to-moderate explosions had occurred at Tungurahua, which were accompanied by Strombolian activity, gas-and-ash emissions, and loud roaring sounds. Seismicity was dominated by tremor and long-period earthquakes.
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.
Sources: Instituto Geofísico-Escuela Politécnica Nacional (IG), Washington Volcanic Ash Advisory Center (VAAC)