Report on Llaima (Chile) — June 2010
Bulletin of the Global Volcanism Network, vol. 35, no. 6 (June 2010)
Managing Editor: Richard Wunderman.
Llaima (Chile) Substantial April 2009 eruption had three lava flows
Please cite this report as:
Global Volcanism Program, 2010. Report on Llaima (Chile) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 35:6. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN201006-357110.
38.692°S, 71.729°W; summit elev. 3125 m
All times are local (unless otherwise noted)
A new eruptive episode began at Llaima on 1 July 2008 (BGVN 33:08) when a lava flow was seen moving down the W flank and sporadic ash explosions originated from the summit area. Activity continued through most of July, but after an episode of Strombolian activity on 26-27 July only fumarolic emissions were reported by scientists from the Southern Andes Volcanological Observatory (OVDAS) of the Chile National Service of Geology and Mining (SERNAGEOMIN). Additional ash explosions began in the second half of August before the volcano quieted again after 3 September (BGVN 33:08).
During an overflight on 12 September OVDAS scientists observed diffuse gas-and-steam emissions from the external edges of the nested craters in the main crater. Observers in Melipeuco (~ 17 km SSE) reported sporadic gas-and-steam emissions from the main crater the following week of 13-22 September. During another overflight on 21 September, steaming was noted from the NE and W flanks.
OVDAS reported that from 19 to 25 November 2008, observers in the area reported weak and sporadic emissions of water vapor concentrated around the two small craters of the paired pyroclastic cones nested inside the main crater. During this period there had been a slight increase both in the energy and number of long-period earthquakes. Seismic instrumentation was located 20 km from the volcano. A few episodes of short duration tremor (averaging 20 RSAM units) along with weak and occasional steam emissions suggested that the seismicity was of superficial origin.
On 11 December two small debris avalanches descended the W flank through an ice channel. Fumarolic activity gradually increased after mid-December; on 22 December there were two weak ash emissions. Meltwater from heavy snowfall on the preceding day was probably responsible for this phreatomagmatic activity.
On 3 January 2009 the two monitoring cameras captured a total of 37 phreatomagmatic explosions over about 14 hours; the plumes of gases and tephra rose 100 m before becoming disconnected from their source. The emissions came from three distinct points within the intra-crater cone. On two occasions spatters of lava impacted the slope of the intra-crater cone and its base. Rockfalls also descended the SE flank of Pichillaima cone, Llaima's secondary summit.
On 2-3 April 2009, OVDAS reported that seismicity from Llaima increased in frequency and amplitude and evolved into continuous tremor. Steam plumes with small amounts of ash were emitted. Late on 3 April, observers reported incandescence from the main crater. Weak Strombolian explosions were produced in the N cone inside the crater. Five settlements were put on alert, including Vilcun and Curacautin, where late on 4 April evacuations began due to lava and ash eruptions. That day, rhythmic Strombolian explosions occurred in the main crater from two nested pyroclastic cones. Incandescent tephra was ejected ~ 700 m above the crater. The Alert Level was raised to Red, the highest state, and the surrounding Conguillio National Park was closed.
The Oficina Nacional de Emergencia, Ministerio del Interior, (ONEMI) reported that, on 4 April, fine ash fell in Lago Lake in the Conguillío National Park and a lava flow 1 km long traveled W towards the Calbuco River. Access to local parks was restricted and 12 people self-evacuated. Later that day, authorities evacuated 71 additional people in high-risk areas, mainly due to the potential for lahars along the Calbuco River and other waterways swollen with volcanic ash.
OVDAS reported that Strombolian activity continued on 5 April (figure 29). A dark gray ash plume drifted E; heavy ashfall was reported in Lago Verde. A lahar traveled NNE down the Captrén River and lava continued to travel down the W flank. On 6 April continuous explosions were observed from Melipeuco (17 km SSE). Lahars again traveled down the Captrén River. Occasionally, gas-and-ash plumes were seen which drifted E and ash fell in areas to the E. Heavy ashfall and lapilli up to 1.5 cm in diameter fell in the National Park areas between Conguillio Lake 10 km ENE, and the Arcoiris Lake less than 10 km ENE.
|Figure 29. Photo of Strombolian activity from the intra-crater cones at Llaima on 5 April 2009. Courtesy of Reuters.|
After 6 April activity declined quickly until reaching a low level characterized by small amounts of ash emissions. On 7 April, gas and ash emitted from multiple points formed a plume that rose ~ 1 km above the summit and drifted NE. The flanks were covered with bombs, lapilli, and ash. An overflight on 7 April observed the main crater completely obscured by a large pyroclastic cone with four inactive craters. Two lava flows descended the W flank. The more southerly lava flow was about 4.5 km long and melted part of the glacier, causing a lahar towards the Calbuco River. The more northerly lava flow was similar in length, and branched off into two 1-km-long flows; it also caused a lahar. On the NE flank, a lava flow that originated from the base of the pyroclastic cone caused lahars that descended into the valley between Curacautín (30 km NNW) and the Conguillío National Park.
During 7-10 April, there was intermittent incandescence from a lava flow at the SW base of the pyroclastic cone. Incandescent blocks originating from the lava flow descended W. On 8 April, gasses emitted from multiple points on the pyroclastic cone formed a plume that drifted NE. Preliminary calculations indicated that the height of the pyroclastic cone exceeded the top of the main crater by ~ 70 m, making the new summit elevation 3,240 m. During 9-10 and 13-14 April, gas and steam plumes rose from the pyroclastic cone; on 14 April, fumarolic activity from the pyroclastic cone was again noted. On 16 April, NASA's Earth Observing-1 satellite passed overhead and documented areas of ash-covered snow W of the summit.
On 24 April ash plumes originating from an area ~ 700 m down the E flank rose ~ 500 m and drifted E. Steam emissions that accompanied the ash plumes indicated that the point of activity came from underneath the glacier. The activity lasted about 1.5 hours. During 28 April-11 May, OVDAS reported sporadic incandescence from an area in the SW part of the main crater. Blocks occasionally rolling down the W flank were seen on a web camera.
During 5-11 May, tephra was ejected from an area on the E flank and, during the night, incandescence originated from this area. During the daytime, observers reported that an almost continuous orange brown plume rose ~ 200 m. Sporadic incandescence also came from an area in the SW part of Llaima's main crater, corresponding to a small active outcrop of lava. Steam plumes rose from the same area continued until 18 May. MODVOLC data reflects the dramatic thermal activity between 4 April and 14 April.
On 26 May 2009, after a period of unusually heavy rain, a 500 m-long fissure on Lliama's the upper E flank began to emit dense steam clouds. On the following day, small amounts of ash were observed mixed in with the water vapor, and on 28 May both the amount of vapor and the ash content increased. On 1 June, after further bad weather, the energy of the intermittent emissions along the fissure further increased. A powerful phreatic eruption began at 1120. The eruption ceased by 1200, and during that afternoon only one small subsequent eruption was observed. Since the phreatic fissure eruptions began, seismicity had remained at normal levels but the number and energy of LP (long period) earthquakes had increased.
During an overflight of Llaima on 1 June 2009 observers reported a 2 km2 area with an elevated temperature on the E flank. Several small areas emitted gas, and a small cone was forming ~ 800 m below the crater. The observers also saw an E-trending, ~ 300m-long fissure located 200 m from the main crater's rim. Brown ash and steam plumes were emitted from different areas of the fissure. The irregularly-shaped summit crater had a few weak fumaroles. During 5-8 June, OVDAS reported increased seismic tremor. Incandescence from an area in the SW part of Llaima's main crater continued to correspond to a small active outcrop of lava. On 6 June, incandescence emanated from a small point along the E-flank fissure. Gas and steam was emitted from an area W of the main crater. The camera in Melipueco again showed glow on the NW inner margin of the main crater during 9-16 June, and occasional steam emissions with minor amounts of ash were also seen from the E flank. From 12 June on there was no evidence of lateral or summit eruption, although inclement weather masked views of the mountain.
An OVDAS report dated 3 July 2009 indicated that seismicity remained similar to the previous week, although there was an increase in the number of low amplitude long-period earthquakes, up to 40/hour. However, they detected two to three higher-energy earthquakes per day; along with weak tremor. A continuing increase of the long-period type earthquakes observed during the previous three days was interpreted to indicate the potential for an eruptive event. Only steam was visible in sectors where previously there have been lava flows.
On 14 November 2009, cameras operated by OVDAS showed steam-and-gas plumes rising from the main crater and E flank. These emissions continued until 1 December. Although seismicity generally decreased, a new type of long-period, low-frequency earthquake was detected. An overflight on 4 December revealed fumarolic activity and some SO2 emissions coming mainly from fissures on the N crater wall and outer E and W flanks.
During 20 January-9 February 2010, cameras showed steam-and-gas plumes rising from the main crater. Seismic signals (tremor and volcano-tectonic earthquakes) had characteristics that indicated fluid movement. On 22 January 2010, OVDAS reported that seismicity had decreased during the previous few weeks to background levels.
OVDAS reported that on 4 March 2010 seismicity increased. During an overflight that same day, scientists observed emissions of gas and steam from the main crater. Photographs were compared to those taken on 21 February and showed no significant changes in morphology. The rate of sulfur dioxide emissions had increased, however. Scientists also noted deposits from a large rockfall along with fracturing of the glacier, especially on the upper N and NW flanks. During 5-22 March seismicity generally decreased to levels characteristic prior to the 27 February earthquake; however a significant number of earthquakes that indicated fluid movement in the volcano continued to be registered. Gas-and-steam plumes rose 100 m from their source.
On 15 April 2010 seismicity increased and tremor was detected; however, OVDAS reported that during 1-14 May seismicity decreased to moderate levels. Small white fumaroles that rose from the main crater were seen through web cameras.
Geologic Background. Llaima, one of Chile's largest and most active volcanoes, contains two main historically active craters, one at the summit and the other, Pichillaima, to the SE. The massive, dominantly basaltic-to-andesitic, stratovolcano has a volume of 400 km3. A Holocene edifice built primarily of accumulated lava flows was constructed over an 8-km-wide caldera that formed about 13,200 years ago, following the eruption of the 24 km3 Curacautín Ignimbrite. More than 40 scoria cones dot the volcano's flanks. Following the end of an explosive stage about 7200 years ago, construction of the present edifice began, characterized by Strombolian, Hawaiian, and infrequent subplinian eruptions. Frequent moderate explosive eruptions with occasional lava flows have been recorded since the 17th century.
Information Contacts: Observatorio Volcanológico de los Andes del Sur (OVDAS), Observatorio Volcanológico de los Andes del Sur-Servico Nacional de Geologia y Mineria; Southern Andes Volcanological Observatory-National Geology and Mining Service (SERNAGEOMIN), Avda Sta María No. 0104, Santiago, Chile; Oficina Nacional de Emergencia - Ministerio del Interior (ONEMI), Ministerio del Interior, Chile (URL: http://www.onemi.cl/); NASA Earth Observatory (URL: http://earthobservatory.nasa.gov/); ; Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Reuters (URL: http://www.reuters.com/).