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PUYEHUE (Puyehue-Cordón Caulle): Hazard and damage!

The long lasting eruption of Puyehue-Cordón Caulle, which started on 4. June 2011, has a tremendous impact in southern Chile and western Argentina.

Images: NASA sat. and MODIS infrared images

Puyehue 12

MODIS image Feb.12


In June 2011, some fractures opened at Puyehue volcano complex as the beginning of a quite long lasting eruption. More than 600 km south of Chiles capital Santiago de Chile, this area of the 4000 km long country has many active volcanoes. If you look south from Puyehue, you can see nearby volcanoes of Puntiagudo (last eruption in 1850), Osorno (last eruption in 1869) and Calbuco (last eruption in 1972). To the north you can spot Cerran los Venados (last eruption in 1979) and Mocho (last eruption 1864). Puyehue itself has had it's last eruption in 1990. It meens, that volcanic eruptions are common in this area and that people deal with the threat and problems caused by eruptions since centuries. This is not just for Chile, it's as well the fact for neighbouring Argentina to the east, which has own active volcanoes of course. Actually, Argentina get's sometimes more problems with pyroclastic (ash and pumice) fall out than chilean terretories, where the erupting volcano is hosted. This is due to westerly wind directions to be most common.

When Puyehue started erupting, not only pyroclastic lava was ejected violently into the athmosphere(up to 12 km altitude), as well lava flows occured at some fissures. But both did not happen inside the 2.4 km wide summit caldera (crater), it all happened some kilometers east of it. The lava flows in this bush land and forest area did not cause proplems for the people living around the volcano, but the fine volcanic pyroclastics (ash) travelling for hundreds of kilometers away, did so. First, airtraffic was disturbed many times, the farmland was covered under layers of ash so many times, that farmers gave up to live and work there anymore. Governments supported these farmers to move out of this area, specially on the argentinian side towards the region of Bariloche, where wind brought ash too often. Volcanic dust is relatively unhealthy to humans and of course to animals. To live in volcanic polluted surroundings, it's tough and difficult. You end up cleaning and protecting your whatever belongings. People cleaned grass land for their stock with water out of pipes to give these animals a chance of eating a clean diet. People also realized, what fine volcanic powder is doing inside electronic devices and doing to smooth and polished surfaces - destroying and scratching. The impact for the nature - some natinal parks are affected - and infratructures are getting worse.

In general, the duration of an eruption is as important for the impact, as the ammount and energetic force of an eruption. With this eruption episode at Puyehue, the ammount of effusive and explosive lava is not on a very big scale so far (well, big enough), but the duration of this eruption is getting quite long. In early 2012, we count already more than half a year with explosive activity most of this time. Not strong some times, but still with kilometer high eruption clouds being drifted away by the wind. In the dry summer from December until March, the vegetation does not get cleaned by rain quite often, so that some plants die, while others stay in a very bad stage. Lakes do stay polluted, which has affects for local drinking water supply, the fish population and even tourism. And nobody knows how long this eruption will go on. It could last many more mounths.

All images below from Chris Weber VEI (c)2012, observation (visits) between 24 Dec.2011 until 2 Jan. 2012.
Puyehue Puyehue Puyehue
Images from left: Areal view to the eruption center; Hundreds of kilometers ash drift; Ash cloud over the volcano
Puyehue Puyehue Puyehue
Images from left: Lake shores are lined with pumice; People lope along through pumice in the lake; Eruption at night
Puyehue Puyehue Puyehue
Images from left: Red glow during the night; Explosive eruption; Ash cloud is growing some kilometers high
Puyehue Puyehue Puyehue
Images from left: Wind brings fine ash; Ash is covering hundreds of square km; Sunset behind the ash cloud
Puyehue Puyehue Puyehue
Images from left: Summit caldera full of pumice; pumice bombs partly broken; Very unstable snow, ash and pumice layers
Puyehue Puyehue Puyehue
Images from left: The volcano covered under ash; Demaged forest; Farmland suffers under the impact of ash

Abstract from GVN:

The Puyehue-Cordón Caulle volcanic complex (PCCVC) is a large NW-SE-trending late-Pleistocene to Holocene basaltic-to-rhyolitic transverse volcanic chain SE of Lago Ranco. The 1799-m-high Pleistocene Cordillera Nevada caldera lies at the NW end, separated from Puyehue stratovolcano at the SE end by the Cordón Caulle fissure complex. The Pleistocene Mencheca volcano with Holocene flank cones lies NE of Puyehue. The basaltic-to-rhyolitic Puyehue volcano is the most geochemically diverse of the PCCVC.
The flat-topped, 2236-m-high Puyehue volcano was constructed above a 5-km-wide caldera and is capped by a 2.4-km-wide summit caldera of Holocene age. Lava flows and domes of mostly rhyolitic composition are found on the eastern flank of Puyehue. Historical eruptions originally attributed to Puyehue, including major eruptions in 1921-22 and 1960, are now known to be from the Cordón Caulle rift zone. The Cordón Caulle geothermal area, occupying a 6 x 13 km wide volcano-tectonic depression, is the largest active geothermal area of the southern Andes volcanic zone.

Source: Global Volcanism Program Smithsonian Institution (c)2012

Volcano News form 2011! Source: Global Volcanism Program Smithsonian Institution and others (c)2011

1 June-7 June 2011

OVDAS-SERNAGEOMIN reported that between 2000 on 2 June and 1959 on 3 June about 1,450 earthquakes at Puyehue-Cordón Caulle were detected, or an average of about 60 earthquakes per hour. The earthquakes were mostly hybrid and long-period, and located in the SE sector of the Cordón Caulle rift zone at depths of 2-5 km. SERNAGEOMIN scientists along with regional authorities flew over the volcano, noting no significant changes. The Alert Level remained at 4, Yellow. Area residents reported feeling earthquakes during the evening of 3 June through the morning of 4 June.

For a six-hour period on 4 June, seismicity increased to an average of 230 earthquakes per hour, at depths of 1-4 km. About 12 events were magnitudes greater than 4, and 50 events were magnitudes greater than 3. The Alert Level was raised to 5, Red. ONEMI reported that the border crossing into Argentina was closed and about 700 local people were to start evacuating. Later, an explosion from Cordón Caulle produced a 5-km-wide ash-and-gas plume that rose to an altitude of 12.2 km (40,000 ft) a.s.l. as noted by OVDAS scientists. The plume drifted S at 5 km altitude, and W and E at 10 km altitude. The Alert Level was raised to 6, Red. ONEMI reported the continuation of evacuations and increased the potential number of evacuees to 3,000. ONEMI also reported that the National Director of SERNAGEOMIN noted that lava was not detected, but pyroclastic flow deposits were observed. Residents reported a strong sulfur odor and significant ash and pumice fall. During 4-5 June ashfall several centimeters thick was reported in San Carlos de Bariloche, 100 km SE in Argentina, and surrounding areas.

Based on analyses of satellite imagery, SIGMET notices, and information from the Puerto Montt Flight Information Region (FIR), the Buenos Aires VAAC reported that on 4 June ash plumes rose to altitudes of 10.7-13.7 km (35,000-45,000 ft) a.s.l. and drifted 870 km ESE. Diffuse gas-and-steam plumes drifted W. The next day an ash plume continued to rise to altitudes of 10.7-12.2 km (35,000-40,000 ft) a.s.l. and had drifted as far as 1,778 km ESE, over the coast of Argentina, and out into the Atlantic Ocean. A portion of the plume drifted WSW. News outlets reported that flights in southern Argentina were canceled during 4-5 June. On 6 June the continuous ash plume changed direction and was blown ENE as far as 178 km while the previous portion of the plume continued to drift ESE over the ocean. On 7 June the VAAC reported continuous emissions. Ash plumes rose to altitudes of 5.5-9.8 km (18,000-32,000 ft) a.s.l. and were 65-95 km wide. A large area of ash continued to drift E over the Atlantic Ocean. News articles noted that some flights in Paraguay and Chile were cancelled and about 4,000 people had evacuated. News photos showed ashfall and people collecting pumice in San Martin de los Andes, Argentina, 80 km NE.

Sources: Servicio Nacional de Geología y Minería (SERNAGEOMIN), Oficina Nacional de Emergencia - Ministerio del Interior (ONEMI), Buenos Aires Volcanic Ash Advisory Center (VAAC), Earth Observatory, National

8 June-14 June 2011

OVDAS-SERNAGEOMIN reported that the eruption from the Cordón Caulle rift zone, part of the Puyehue-Cordón Caulle volcanic complex, that began on 4 June continued on 5 June. At least five pyroclastic flows were generated from partial collapses of the eruptive column and traveled N in the Nilahue River drainage. The pyroclastic flows were possibly 10 km long. On 6 June the continuous ash plume changed direction and was blown ENE as far as 178 km while the previous portion of the plume continued to drift ESE over the ocean. On 7 June the Buenos Aires VAAC reported that ash plumes rose to altitudes of 5.5-9.8 km (18,000-32,000 ft) a.s.l. and were 65-95 km wide.

OVDAS-SERNAGEOMIN reported that on 8 June satellite imagery showed a 1,200-km-long eruption plume drifting NE, then SE over the Atlantic Ocean. Personnel working in the area reported that the ash plume rose 7.5 km above the crater. On 9 June climatologic conditions prevented ground-based observations of the plume, however satellite imagery showed a 200-km-long plume drifting NE. Pumice and vitreous tephra had accumulated in many area lakes and rivers, and ash had turned many rivers darker. Despite poor visibility due to meteorological conditions on 10 June, the plume was observed to have risen 3.7 km above the crater and drifted SE. News articles stated that flight disruptions continued in Argentina and Uruguay, and flights from airports in Brazil had been cancelled. On 11 June the plume was whiter than previous days and rose to heights 4-4.5 km above the crater and drifted 350 km E. A dispersed plume was detected as far as 600 km ENE. Some flights resumed in affected parts of Chile, Argentina, and Uruguay.

An overflight on 11 June revealed that the vent was located at the head of the Nilahue River's basin, immediately to the N of the 1960 eruption fissure location. Abundant amounts of ash had accumulated around the vent as well as to the E and SW. Ash plumes rose 4-4.5 km above the crater; an explosion that day caused an ash plume to rise 8 km above the crater. On 12 June seismicity was relatively stable except for four hybrid earthquakes and a pulse of tremor that lasted about 2 hours and 40 minutes. A series of explosions (up to 8 events per minute) were also registered. Very dense, dark gray ash plumes rose 8 km above the crater. Satellite imagery showed a distinct eruption plume drifting 300 km E, with a diffuse plume reaching 1,000 km ENE. According to news articles, the ash plume that had been drifting mostly E since the beginning of the eruption had reached Australia and beyond, causing flight cancellations in southern Australia and New Zealand.

Scientists aboard an overflight on 13 June observed the plume height oscillating and noted that the eruptive vent diameter was 300-400 m. Gas-and-steam plumes rose from two or three locations along the same fissure as the eruptive vent. Pulses of tremor were associated with dark gray ash plumes that rose 9 km above the crater. Ashfall and column collapses were noted. At night incandescence from the base of the plume reached 1.5-2 km high. Satellite imagery showed the plume drifting 250 km SE. On 14 June explosions generated pyroclastic flows (that traveled N), with associated ash-and-gas plumes. Based on analysis of satellite imagery, the VAAC stated that ash plumes rose to altitudes of 5.5-7.6 km (18,000-25,000 ft) a.s.l. while previously emitted ash plumes drifted NE, E, and SE at altitudes of 0.9-3 km (3,000-10,000 ft) a.s.l. SERNAGEOMIN reiterated that the Alert Level remained at 6, Red.

Sources: Servicio Nacional de Geología y Minería (SERNAGEOMIN), Buenos Aires Volcanic Ash Advisory Center (VAAC), BBC, AAP, Associated Press1

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