Sangay

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  • Volcanic Region
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  • Last Known Eruption
  • 2.005°S
  • 78.341°W

  • 5286 m
    17338 ft

  • 352090
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Most Recent Weekly Report: 22 May-28 May 2013


Based on a pilot report, the Washington VAAC reported that on 23 May an ash plume from Sangay drifted W at an altitude of 7.6 km (25,000 ft) a.s.l. Weather clouds prevented satellite image views of the plume.

Source: Washington Volcanic Ash Advisory Center (VAAC)


Most Recent Bulletin Report: February 2014 (BGVN 39:02)


Absence of evidence for ongoing eruption; new hazard maps

Previously reported activity from Sangay volcano (figure 11) included ash plumes as late as 23 May 2013 and satellite infrared thermal alerts ending in early May 2013 (BGVN 36:01). In that previous report, satellite thermal alerts from the MODVOLC system were noted to have persisted and as late as 4 May 2013. That lack of alerts continued as late as 16 July 2013 when the MODVOLC website was last checked. Since that reporting, there have been no new updates regarding Sangay on the website of the Instituto Geofisico (IG), the aviation reports have not mentioned Sangay, and other news of Sangay behavior has also been generally lacking.

Figure 11. (Inset at bottom) A regional map showing Sangay with respect to large rivers and other features surrounding Sangay. Orange line is the PanAmerican highway, which passes near Río Bamba on the map's N. Major rivers (blue) are primary routes of lahars. (Main map) A hazards map for Sangay made with hazards focus and compiling the results of multiple kinds of modeling. Key (in Spanish) notes that the upper three colors were based on slope angle (H/L) with text noting gradation of hazards in those regions from pyroclastic flows, lava flows, ash falls, volcanic bombs, rock falls, and proximal lahars. The lower three colors on the key represent inferred gradations of lahar hazard at distance from the volcano. Dashed envelopes in red refer to boundaries for small and moderate sizes of ash falls. White line shows inferred boundary for an E directed debris avalanche. Base map is from the Instituto Geografico Militar (IGM). Taken from an online poster by Ordóñez and others, 2014).

Absence of MODVOLC and aviation alerts does not necessarily translate to a lack of eruptions. The MODVOLC system imposes a reasonably high threshold to the infrared data acquired from space. Factors such as weather conditions, snow pack, and geometry of the vent area may play a role. Emissions of spatter, ash fall, and small pyroclastic flows could easily be missed. Assessments are generally best made in conjunction with information at the volcano. The current eruption began on 8 August 1934 and is thus far confirmed only through 23 May 2013.

Hazard modeling and products. In late 2013 to early 2014 IG released a poster discussing Sangay hazards (Ordóñez and others, 2014), some of the results of which we reprint here (figures 11, 12, and 13). Figure 11 contains IGEPN's recently published a map of volcanic hazards associated with Sangay, which resides in the Cordillera Real between the cities of Río Bamba and Macas. The IG and others have generally considered Sangay one of the most active volcanoes in South America. The poster noted historical records of its eruptive activity dating back to 1628 (Hall, 1977) and in the last century some important periods of activity were recorded during 1903, 1934-1937, 1941-1942, 1975-1976, and 1995 to the present (Monzier et al.. 1999). Observations of surface activity carried out in the past 40 years allowed scientists to recognize some important morphological changes at the summit of the volcano, including the emergence of new craters, dome growth, extrusion of lava flows, local explosions and ash emissions, and relatively small pyroclastic flows.

Figure 12. Modeled ash fall blanket from a hypothetical eruption at Sangay of moderate size. The key (in Spanish) refers to the colors in the key and on the isopach map, with thicknesses in millimeters. Taken from an online poster by Ordóñez and others (2014).
Figure 13. Modeled ash fall blanket from a hypothetical eruption at Sangay of large size. The key (in Spanish) refers to the colors in the key and on the isopach map, with thicknesses in millimeters. Taken from an online poster by Ordóñez and others (2014).

A larger suite of volcanic hazards models is not shown here but includes results VolcFlow. Ash3D, Tephra2, and LAHARZ. The data used for the simulations were obtained from the few geological studies in this volcano (Hall, 1977; Monzier et al, 1999; Johnson et al, 2003). Sangay is judged in some ways analogous to Tungurahua volcano, because of its chemical composition, and it similar lava rheology and eruptive style of volcanic flows.

During August-September 2013, IG installed seismic monitoring instruments (broad band and infrasound ) and for the measurement of sulfur dioxide (SO2) in the southwestern flank of the volcano Sangay. These tools facilitate the monitoring of internal and surface activity of the volcano which will give an early warning of a potential hazards.

With regard to monitoring, during August-September 2013 IG personnel installed ~4 km southwest of Sangay volcano, permanent telemetered monitoring system consisting of a broadband seismic sensor, infrasound, and gas monitoring.

Figures 12 and 13 show the respective modeled results for a moderate and large eruption. To define the zones affected by ash fall, the modeling used the following computer routines based on assumptions and approaches discussed in the literature: Ash3d (Mastin and others, 2012) and Tephra2 (Banadonna and others, 2005). Some input data came from inferences and interpretations of descriptions by Monzier and others (1999) and from analogy with recent eruptions at Tungurahua. Plume heights were assumed to reach 10-15 km in altitude and the magma volumes in the plumes were assumed to be on the order of 0.001-0.005 km3 (dense-rock equivalent, DRE). Wind field data came from the Global Forecast System (NOAA, US National Weather Service, Environment Modeling Center). LAHARZ (Schilling, 1998), a modeling approach, was also taken to estimate the extent and coverage of lahars seen in figure 11. (The poster includes other maps on this topic as well.)

References. Bonadonna, C, Connor CB, Houghton BF, Byrne M, Laing A, Hincks T., 2005, Probabilistic modeling of tephra dispersal: Hazard assessment of a multi-phase eruption at Tarawera, New Zealand; J. Geophys. Res., 110, B03203.

Hall M. (1977). El Volcanismo en Ecuador. Publicación del Instituto Panamericano de Geografía e Historia, Sección nacional del Ecuador, Quito. 120pp.

Mastin, L, Schwaiger H, Denlinger R., 2012, User's Guide to Ash3d: A 3-D Eulerian Atmospheric Tephra Transportation and Dispersion Model, U.S. Geological Survey Open File Report.

Monzier M, Robin C, Samaniego P, Hall M, Cotten J, Mothes P, Arnaud N., 1999, J. Volcanol. Geotherm. Res. 90, 49-79.

Ordóñez J., Vallejo S., Bustillos J., Hall M., Andrade D., Hidalgo S., and Samaniego P., (Document created, December 2013; Accessed online July 2014), Volcan Sangay---Peligros Volcanicos Potenciales, Instituto Geofísico, Escuela Politécnica Nacional (IG-ESPN) (URL: http://www.igepn.edu.ec/volcan-sangay/mapa-de-peligros.html ).

Schilling S. (1998). LAHARZ: GIS programs for automated mapping of lahar-inundation hazard zones. US Geological Survey Open-File Report 98-638; 79 pp.

Information Contacts: Instituto Geofísico-Escuela Politécnica Nacional (IG), Casilla 17-01-2759, Quito, Ecuador (URL: http://www.igepn.edu.ec ); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: http://www.ssd.noaa.gov/VAAC/); and Hawai'i Institute of Geophysics and Planetology (HIGP) MODVOLC 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://hotspot.higp.hawaii.edu/).

Index of Weekly Reports


2013: January | February | April | May
2012: January | March | May | June | July
2011: January | February | October | November
2010: January | February | April | May | July | August | September | October | December
2009: February | March | June | July | September | October | November | December
2008: September | December
2007: January | February | March | May | July | August | September | October | December
2006: October | November | December
2005: October
2004: January | April | December

Weekly Reports


22 May-28 May 2013

Based on a pilot report, the Washington VAAC reported that on 23 May an ash plume from Sangay drifted W at an altitude of 7.6 km (25,000 ft) a.s.l. Weather clouds prevented satellite image views of the plume.

Source: Washington Volcanic Ash Advisory Center (VAAC)


24 April-30 April 2013

Based on analyses of satellite imagery and a SIGMET aviation notice, the Washington VAAC reported that on 26 April two brief ash emissions from Sangay drifted SW and dissipated within 20 km. A thermal anomaly was visible in infrared satellite images.

Source: Washington Volcanic Ash Advisory Center (VAAC)


10 April-16 April 2013

Based on analyses of satellite imagery, the Washington VAAC reported that on 11 April an ash plume from Sangay drifted W.

Source: Washington Volcanic Ash Advisory Center (VAAC)


20 February-26 February 2013

According to the Washington VAAC, on 22 February a pilot observed an ash plume from Sangay that rose to an altitude of 7.6 km (25,000 ft) a.s.l. and drifted SW. Due to cloud cover in the area, neither satellite image analysis nor the Instituto Geofísico-Escuela Politécnica Nacional (IG) could confirm an ash emission. Ash plumes were not detected in cloudy satellite image views during 23-24 February, but a thermal anomaly was detected on 24 February.

Source: Washington Volcanic Ash Advisory Center (VAAC)


23 January-29 January 2013

Based on a pilot report, analyses of satellite images, and information from the Guayaquil MWO, the Washington VAAC reported that a possible eruption from Sangay before 1210 on 25 January may have produced ash plumes. Cloud cover prevented satellite observations of emissions during 25-26 January, although a weak thermal anomaly was detected.

Source: Washington Volcanic Ash Advisory Center (VAAC)


25 July-31 July 2012

According to the Washington VAAC, a pilot reported that on 29 July an ash plume from Sangay rose to an altitude of 6.7 km (22,000 ft) a.s.l. and drifted W. A plume that may have been mostly gas was detected in satellite images pushing through the metrological cloud deck and drifting W.

Source: Washington Volcanic Ash Advisory Center (VAAC)


18 July-24 July 2012

According to the Washington VAAC, a pilot reported that a possible eruption from Sangay occurred prior to 1438 on 20 July. Ash was not observed in satellite imagery and a SIGMET issued for the event was later cancelled.

Source: Washington Volcanic Ash Advisory Center (VAAC)


4 July-10 July 2012

According to the Washington VAAC, a thermal anomaly on Sangay was detected in satellite imagery during 4-6 July.

Source: Washington Volcanic Ash Advisory Center (VAAC)


6 June-12 June 2012

According to the Washington VAAC, a pilot observed an ash plume from Sangay on 6 June that rose to an altitude of 6.1 km (20,000 ft) a.s.l. and drifted N. Meteorological clouds prevented satellite image views. A pilot observed ash drifting E on 10 June.

Source: Washington Volcanic Ash Advisory Center (VAAC)


30 May-5 June 2012

According to the Washington VAAC, a pilot observed an ash plume from Sangay on 4 June that rose to an altitude of 7.9 km (26,000 ft) a.s.l. and drifted E. Ash was not detected in satellite imagery.

Source: Washington Volcanic Ash Advisory Center (VAAC)


23 May-29 May 2012

Based on a SIGMET report, the Washington VAAC reported a possible eruption and ash plume from Sangay on 28 May. A later notice stated that a pilot reported an ash plume at an altitude of 6.1 km (20,000 ft) a.s.l. Ash was not identified in satellite imagery.

Source: Washington Volcanic Ash Advisory Center (VAAC)


21 March-27 March 2012

According to the Washington VAAC, a pilot observed an ash plume from Sangay on 22 March that rose to an altitude of 8.2 km (27,000 ft) a.s.l. Cloud cover prevented satellite observations.

Source: Washington Volcanic Ash Advisory Center (VAAC)


18 January-24 January 2012

Based on information from pilots and the Guayaquil MWO, an ash plume from Sangay was reported drifting S and SE on 23 January. Ash was not detected in partly-cloudy satellite imagery. On 24 January a hotspot was visible on satellite imagery.

Source: Washington Volcanic Ash Advisory Center (VAAC)


4 January-10 January 2012

Based on information from Guayaquil MWO and a pilot report, a possible ash plume from Sangay was reported on 8 January. Ash was not detected in partly-cloudy satellite imagery.

Source: Washington Volcanic Ash Advisory Center (VAAC)


16 November-22 November 2011

The Washington VAAC reported that on 20 November an ash plume from a possible eruption at Sangay was observed by a pilot and drifted at an altitude of 5.9 km (19,500 ft) a.s.l. Ash was not detected in partly-cloudy satellite imagery.

Source: Washington Volcanic Ash Advisory Center (VAAC)


19 October-25 October 2011

Based on analyses of satellite imagery, the Washington VAAC reported that on 25 October a gas plume from Sangay, which possibly contained ash, drifted 75 km E. Ash was not identified in subsequent images.

Source: Washington Volcanic Ash Advisory Center (VAAC)


5 October-11 October 2011

Based on information from the Guayaquil MWO and a pilot observation, the Washington VAAC reported that on 11 October an ash plume from Sangay from a possible eruption rose to an altitude of 6.7 km (22,000 ft) a.s.l. and drifted W. Ash was not observed in satellite imagery.

Source: Washington Volcanic Ash Advisory Center (VAAC)


23 February-1 March 2011

The Washington VAAC reported that on 23 February a pilot observed ash from Sangay. No ash was confirmed in a small cloud identified in satellite imagery drifting SSE.

Source: Washington Volcanic Ash Advisory Center (VAAC)


26 January-1 February 2011

Based on analyses of satellite imagery, the Washington VAAC reported that on 27 January small ash clouds from Sangay drifted N and quickly dissipated.

Source: Washington Volcanic Ash Advisory Center (VAAC)


19 January-25 January 2011

Based on a pilot observation, the Washington VAAC reported that on 20 January an ash plume from Sangay rose to an altitude of 7.6 km (25,000 ft) a.s.l. Ash was not detected in satellite imagery.

Source: Washington Volcanic Ash Advisory Center (VAAC)


12 January-18 January 2011

Based on a pilot observation, the Washington VAAC reported that on 12 January an ash plume from Sangay rose to an altitude of 6.7 km (22,000 ft) a.s.l. and possibly drifted more than 45 km SW. A thermal anomaly was detected in satellite imagery.

Source: Washington Volcanic Ash Advisory Center (VAAC)


1 December-7 December 2010

Based on information from Guayaquil MWO, the Washington VAAC reported ash from Sangay on 5 December; weather clouds prevented satellite observations. IG noted elevated seismicity.

Source: Washington Volcanic Ash Advisory Center (VAAC)


27 October-2 November 2010

The Washington VAAC reported that on 29 October a thermal anomaly from Sangay was seen in satellite imagery. A narrow steam-and-gas plume possibly containing some ash was also detected.

Source: Washington Volcanic Ash Advisory Center (VAAC)


13 October-19 October 2010

The Washington VAAC reported that on 14 October a pilot noted an ash plume from Sangay; however, an analysis of satellite imagery revealed only gas plumes drifting NW.

Source: Washington Volcanic Ash Advisory Center (VAAC)


6 October-12 October 2010

The Washington VAAC reported that on 6 October small ash clouds from Sangay were observed by a pilot. The ash clouds were seen in satellite imagery drifting WNW.

Source: Washington Volcanic Ash Advisory Center (VAAC)


15 September-21 September 2010

The Washington VAAC reported that on 21 September an ash plume from Sangay rose to an altitude of 7.6 km (25,000 ft) a.s.l. and was observed by a pilot. Ash was not seen in satellite imagery, although weather clouds were in the area.

Source: Washington Volcanic Ash Advisory Center (VAAC)


8 September-14 September 2010

The Washington VAAC reported that on 10 September a small plume and a thermal anomaly from Sangay were seen in satellite imagery. Based on information from Tegucigalpa MWO, pilot observations, and analyses of satellite imagery, the VAAC reported that on 13 September small plumes of gas with possible ash drifted SW. A thermal anomaly had also been detected for the previous few hours.

Source: Washington Volcanic Ash Advisory Center (VAAC)


1 September-7 September 2010

The Washington VAAC reported that on 5 September an ash plume from Sangay that rose to an altitude of 5.5 km (18,000 ft) a.s.l. was observed by a pilot. Ash was not seen in satellite imagery.

Source: Washington Volcanic Ash Advisory Center (VAAC)


25 August-31 August 2010

The Washington VAAC reported that on 30 August an ash plume was observed near Sangay by a pilot. Ash was not seen in satellite imagery.

Source: Washington Volcanic Ash Advisory Center (VAAC)


18 August-24 August 2010

Based on analyses of satellite imagery, the Washington VAAC reported that on 19 August small ash-and-gas plumes from Sangay drifted about 25 km W and dissipated. Intermittent thermal anomalies were also detected. On 20 August a pilot reported an emission that was not seen in satellite imagery.

Source: Washington Volcanic Ash Advisory Center (VAAC)


21 July-27 July 2010

Based on pilot observations and analyses of satellite imagery, the Washington VAAC reported that on 21 July an ash cloud from Sangay drifted W. During 22-23 July, diffuse plumes drifted 65-115 km W. Occasional thermal anomalies were detected by satellite imagery on 21 and 23 July.

Source: Washington Volcanic Ash Advisory Center (VAAC)


5 May-11 May 2010

The Washington VAAC reported that on 6 May an ash plume from Sangay was seen by a pilot. Ash was not identified in satellite imagery, but a diffuse steam-and-gas plume was seen before weather clouds moved into the area.

Source: Washington Volcanic Ash Advisory Center (VAAC)


21 April-27 April 2010

Based on a pilot observation, the Washington VAAC reported that on 21 April an ash plume from Sangay rose to an altitude of 6.7 km (22,000 ft) a.s.l. Ash was not identified in satellite imagery, although weather clouds were present in the area.

Source: Washington Volcanic Ash Advisory Center (VAAC)


17 February-23 February 2010

Based on pilot observations, the Washington VAAC reported that on 22 February an ash plume from Sangay rose to an altitude of 7.6 km (25,000 ft) a.s.l. Ash was not identified in satellite imagery.

Source: Washington Volcanic Ash Advisory Center (VAAC)


27 January-2 February 2010

Based on pilot observations, the Washington VAAC reported that on 2 February an ash plume from Sangay rose to an altitude of 8.2 km (27,000 ft) a.s.l. Ash was not identified in satellite imagery, although weather clouds were present in the area.

Source: Washington Volcanic Ash Advisory Center (VAAC)


13 January-19 January 2010

Based on pilot observations, the Washington VAAC reported that on 14 January an ash plume from Sangay rose to an altitude of 7.3 km (24,000 ft) a.s.l. Ash was not identified in satellite imagery, although weather clouds were present in the area.

Source: Washington Volcanic Ash Advisory Center (VAAC)


30 December-5 January 2010

The Washington VAAC reported that during 2-4 January thermal anomalies from Sangay were seen in satellite imagery. On 2 January, a pilot saw an ash plume drifting NW at an altitude of 7 km (23,000 ft) a.s.l. An ash plume was also reported by a pilot the next day.

Source: Washington Volcanic Ash Advisory Center (VAAC)


16 December-22 December 2009

Based on pilot observations, the Washington VAAC reported that on 18 and 21 December ash plumes from Sangay rose to an altitude of 7.9 km (26,000 ft) a.s.l. and drifted W. Ash was not identified in satellite imagery, although weather clouds were present in the area. Thermal anomalies were occasionally detected in the satellite imagery.

Source: Washington Volcanic Ash Advisory Center (VAAC)


25 November-1 December 2009

Based on a pilot observation, the Washington VAAC reported that on 1 December an ash plume from Sangay rose to an altitude of 7.9 km (26,000 ft) a.s.l. and drifted W. Ash was not identified in satellite imagery, although low weather clouds were present in the area. Later that day, an eruption was reported, but ash was again unidentifiable in satellite imagery.

Source: Washington Volcanic Ash Advisory Center (VAAC)


11 November-17 November 2009

Based on analyses of satellite imagery, the Washington VAAC reported that on 16 November small plumes from Sangay, possibly with ash, drifted WNW. A thermal anomaly was also detected.

Source: Washington Volcanic Ash Advisory Center (VAAC)


14 October-20 October 2009

Based on analyses of satellite imagery, the Washington VAAC reported that on 15 October a small plume from Sangay drifted 15 km SW.

Source: Washington Volcanic Ash Advisory Center (VAAC)


30 September-6 October 2009

The Washington VAAC reported that on 4 October a pilot saw an ash plume from Sangay drifting W at altitudes of 5.2-7.6 km (17,000-25,000 ft) a.s.l. Meteorological clouds prevented satellite views of the area. No additional reports of the ash plume were received by the VAAC.

Source: Washington Volcanic Ash Advisory Center (VAAC)


22 July-28 July 2009

Based on a pilot observation, the Washington VAAC reported that on 23 July a possible ash plume from Sangay rose to an altitude of 7.9 km (26,000 ft) a.s.l. The plume was not identified in satellite imagery.

Source: Washington Volcanic Ash Advisory Center (VAAC)


24 June-30 June 2009

Based on a pilot observation, the Washington VAAC reported that on 26 June an ash plume from Sangay rose to an altitude of 7.6 km (25,000 ft) a.s.l. The suspected ash was seen on satellite imagery drifting less than 30 km W.

Source: Washington Volcanic Ash Advisory Center (VAAC)


10 June-16 June 2009

Based on analysis of satellite imagery, the Washington VAAC reported that on 15 June possible small ash plumes from Sangay drifted WNW. A thermal anomaly was detected.

Source: Washington Volcanic Ash Advisory Center (VAAC)


4 March-10 March 2009

Based on pilot observations and analysis of satellite imagery, the Washington VAAC reported that on 10 March an ash plume from Sangay rose to an altitude of 5.5 km (18,000 ft) a.s.l. and drifted W. A thermal anomaly was detected in satellite imagery.

Source: Washington Volcanic Ash Advisory Center (VAAC)


4 February-10 February 2009

Based on pilot observations, the Washington VAAC reported that on 9 February a plume from Sangay rose to an altitude of 7.9 km (26,000 ft) a.s.l. No ash was identified on satellite imagery, but meteoric clouds were also present in the area.

Source: Washington Volcanic Ash Advisory Center (VAAC)


31 December-6 January 2009

Based on a pilot observation, the Washington VAAC reported that on 5 January an ash plume from Sangay rose to an altitude of 7 km (23,000 ft) a.s.l. and drifted S. Ash was not identified on satellite imagery.

Source: Washington Volcanic Ash Advisory Center (VAAC)


10 December-16 December 2008

Based on analysis of satellite imagery, the Washington VAAC reported that a small gas-and-steam plume with some ash rose from Sangay on 16 December.

Source: Washington Volcanic Ash Advisory Center (VAAC)


24 September-30 September 2008

Based on analysis of satellite imagery, information from the Guayaquil MWO, and pilot reports, the Washington VAAC reported that a minor ash plume rose from Sangay on 24 September and drifted WNW.

Source: Washington Volcanic Ash Advisory Center (VAAC)


26 December-1 January 2008

Based on observations of satellite imagery and pilot reports, the Washington VAAC reported that an ash plume from Sangay rose to an altitude of 6.1 km (20,000 ft) a.s.l. on 26 December and drifted SW. A thermal anomaly was seen on satellite imagery during 26-27 December.

Source: Washington Volcanic Ash Advisory Center (VAAC)


10 October-16 October 2007

Based on observations of satellite imagery and pilot reports, the Washington VAAC reported that an ash plume from Sangay rose to an altitude of 7 km (23,000 ft) a.s.l. on 12 October and drifted W.

Source: Washington Volcanic Ash Advisory Center (VAAC)


5 September-11 September 2007

The Washington VAAC reported that ash plumes from Sangay were observed by pilots during 8-9 September. Ash was not detected on satellite imagery.

Source: Washington Volcanic Ash Advisory Center (VAAC)


15 August-21 August 2007

Based on pilot observations, the Washington VAAC reported that an ash plume from Sangay drifted SSE on 19 August. Observations using satellite imagery were inhibited due to cloud cover.

Source: Washington Volcanic Ash Advisory Center (VAAC)


1 August-7 August 2007

Based on pilot observations, the Washington VAAC reported that an ash plume from Sangay rose to an altitude of 5.5 km (18,000 ft) a.s.l. and drifted W on 2 August. Ash was not detected on satellite imagery.

Source: Washington Volcanic Ash Advisory Center (VAAC)


25 July-31 July 2007

Based on pilot observations, the Washington VAAC reported that an ash plume from Sangay rose to an altitude of 6.7-8.2 km (22,000 to 27,000 ft) a.s.l. on 28 July. Ash was not detected on satellite imagery but a weak hotspot could be seen.

Source: Washington Volcanic Ash Advisory Center (VAAC)


18 July-24 July 2007

Based on pilot observations, the Washington VAAC reported that an ash plume from Sangay rose to an altitude of 5.5 km (18,000 ft) a.s.l. and drifted W on 23 July. Ash was not detected on satellite imagery. On 24 July, a diffuse ash plume at an altitude of 5.2 km (17,000 ft) a.s.l. was visible on satellite imagery drifting SW.

Source: Washington Volcanic Ash Advisory Center (VAAC)


4 July-10 July 2007

Based on pilot observations, the Washington VAAC reported that an ash plume from Sangay rose to an altitude between 5.2-7.9 km (17,000-26,000 ft) a.s.l. and drifted W on 3 July.

Source: Washington Volcanic Ash Advisory Center (VAAC)


23 May-29 May 2007

Based on pilot observations, the Washington VAAC reported that an ash plume from Sangay rose to an altitude of 7.3 km (24,000 ft) a.s.l. on 24 May.

Source: Washington Volcanic Ash Advisory Center (VAAC)


2 May-8 May 2007

Based on pilot observations, the Washington VAAC reported that an ash plume from Sangay rose to altitudes of 5.2-7.6 km (17,000-25,000 ft) a.s.l. on 4 May. On 5 May, a possible narrow ash plume was visible on satellite imagery drifting W.

Source: Washington Volcanic Ash Advisory Center (VAAC)


21 March-27 March 2007

Based on information from IG, the Washington VAAC reported that an ash plume from Sangay was present on 22 March. The altitude and drift direction of the plume were not reported.

Source: Washington Volcanic Ash Advisory Center (VAAC)


14 March-20 March 2007

Based on pilot reports and satellite imagery, the Washington VAAC reported that an ash plume from Sangay on 17 March rose to an altitude of 5.2 km (17,000 ft) a.s.l. A hotspot was visible on satellite imagery. A pilot reported an ash plume on 20 March to an unreported altitude.

Source: Washington Volcanic Ash Advisory Center (VAAC)


7 March-13 March 2007

Based on information from IG, pilot reports, and satellite imagery, the Washington VAAC reported that eruptions from Sangay during 12-13 March produced ash plumes that rose to 7 km (23,000 ft) a.s.l. and drifted W. A hotspot was seen on satellite imagery.

Source: Washington Volcanic Ash Advisory Center (VAAC)


28 February-6 March 2007

Based on information from the Guayaquil MWO and satellite imagery, the Washington VAAC reported that an eruption from Sangay on 28 February produced an ash plume that rose to an altitude of 7.6 km (25,000 ft) a.s.l. On 2 March, a diffuse plume and a weak hotspot were seen on satellite imagery. On 5 March, a pilot reported that an ash plume rose to between 5.2-6.1 km (17,000-20,000 ft) a.s.l. and drifted W.

Source: Washington Volcanic Ash Advisory Center (VAAC)


21 February-27 February 2007

The Washington VAAC reported eruptions from Sangay based on information from Guayaquil MWO, IG, pilot reports, and satellite imagery. Ash plumes reached altitudes of 10.7 km (35,000 ft) a.s.l. on 23 February and 6.4 km (21,000 ft) a.s.l. on 25 February. Plumes drifted S and SW, respectively.

Source: Washington Volcanic Ash Advisory Center (VAAC)


7 February-13 February 2007

Based on information from Guayaquil MWO, IG, pilot reports, and satellite imagery, the Washington VAAC reported that eruptions from Sangay during 6-10 and 13 February produced ash plumes that drifted SW, NW, N, and W. Plumes reached altitudes of 9 km (30,000 ft) a.s.l. on 6 February and 6.1 km (20,000 ft) a.s.l. on 9 February. A hotspot was seen on satellite imagery at the summit during 7-9 and 13 February.

Source: Washington Volcanic Ash Advisory Center (VAAC)


31 January-6 February 2007

Based on information from the Guayaquil MWO and satellite imagery, the Washington VAAC reported that an eruption from Sangay on 6 February produced ash plumes that rose to a maximum altitude of 9.1 km (30,000 ft) a.s.l. and drifted SW.

Source: Washington Volcanic Ash Advisory Center (VAAC)


24 January-30 January 2007

Based on information from Guayaquil MWO, the Washington VAAC reported that an eruption from Sangay on 28 January produced an ash plume that rose to an altitude of 6.4 km (21,000 ft) a.s.l.

Source: Washington Volcanic Ash Advisory Center (VAAC)


17 January-23 January 2007

Based on pilot reports, the Washington VAAC reported that an eruption from Sangay produced an ash plume on 20 January. The altitude and direction of the plume were not reported.

Source: Washington Volcanic Ash Advisory Center (VAAC)


10 January-16 January 2007

Based on information from Guayaquil Meteorological Watch Office (MWO), pilot reports, and satellite imagery, the Washington VAAC reported that an eruption from Sangay on 14 January produced an ash plume that rose to an altitude of 6.1 km (20,000 ft) a.s.l. and drifted SW.

Source: Washington Volcanic Ash Advisory Center (VAAC)


27 December-2 January 2007

Based on information from Guayaquil Meteorological Watch Office (MWO) and satellite imagery, the Washington VAAC reported that an eruption from Sangay on 1 January produced an ash plume that rose to an altitude of 5.2 km (17,000 ft) a.s.l.

Source: Washington Volcanic Ash Advisory Center (VAAC)


20 December-26 December 2006

Based on a pilot report, the Washington VAAC reported that an ash plume from Sangay rose to an altitude of 7.6 km (25,000 ft) a.s.l. on 23 December.

Source: Washington Volcanic Ash Advisory Center (VAAC)


29 November-5 December 2006

Based on pilot reports and satellite imagery, the Washington VAAC reported that an eruption from Sangay on 2 December produced an ash plume that rose to an altitude of 8.5 km (28,000 ft) a.s.l. and drifted SW.

Source: Washington Volcanic Ash Advisory Center (VAAC)


22 November-28 November 2006

According to the Washington VAAC, an eruption from Sangay on 22 November produced an ash plume observed on satellite imagery that drifted WNW.

Source: Washington Volcanic Ash Advisory Center (VAAC)


18 October-24 October 2006

Based on a pilot report, the Washington VAAC reported that on 21 October, emission plumes from Sangay reached altitudes of 6.7 km (22,000 ft) a.s.l.

Source: Washington Volcanic Ash Advisory Center (VAAC)


11 October-17 October 2006

Based on information from Guayaquil MWO and a pilot report, the Washington VAAC reported on 11 October that emission plumes from Sangay reached altitudes of 2.7 km (9,000 ft) a.s.l. and drifted W.

Source: Washington Volcanic Ash Advisory Center (VAAC)


26 October-1 November 2005

Based on information from IG, the Washington VAAC reported that ash was seen over Sangay on 26 October at 0758. No ash was visible on satellite imagery.

Source: Washington Volcanic Ash Advisory Center (VAAC)


12 October-18 October 2005

An ash plume emitted from Sangay was visible on satellite imagery on 16 October around 0645. The plume moved SSW very slowly, corresponding to a possible height of ~6.7 km (22,000 ft) a.s.l. By 0900 the plume was too thin to be visible on satellite imagery and thunderstorms developed in the area, further obscuring the ash cloud.

Source: Washington Volcanic Ash Advisory Center (VAAC)


22 December-28 December 2004

According to the Washington VAAC, on 28 December around 0715 satellite imagery showed a plume from Sangay that was most likely composed of steam with little ash. The plume was E of the volcano's summit at a height of ~6.4 km a.s.l. A hotspot was prominent on satellite imagery, but ash was more difficult to distinguish.

Source: Washington Volcanic Ash Advisory Center (VAAC)


28 April-4 May 2004

Based on a pilots report, the Washington VAAC reported that ash from an eruption at Sangay produced a plume to a height of ~6 km a.s.l. on 1 May at 1750. Ash was not visible on satellite imagery.

Source: Washington Volcanic Ash Advisory Center (VAAC)


21 January-27 January 2004

Satellite imagery on 27 January showed a narrow ash plume emitted from Sangay that was at a height of ~6 km a.s.l. and drifting SW.

Source: Washington Volcanic Ash Advisory Center (VAAC)


14 January-20 January 2004

According to the Washington VAAC, satellite imagery showed a plume emitted from Sangay on 14 January around 0500 extendeding ~45 km E. The plume most likely contained ash. During this time a hotspot was also visible on satellite imagery.

Sources: Washington Volcanic Ash Advisory Center (VAAC); New Zealand Herald


Index of Bulletin Reports


Reports are organized chronologically and indexed below by Month/Year (Publication Volume:Number), and include a one-line summary. Click on the index link or scroll down to read the reports.

01/1974 (CSLP 09-74) Continuing eruptive activity with frequent explosions

07/1975 (CSLP 50-75) Continued activity; block lava flows and ash emissions

07/1976 (NSEB 01:10) Explosions, lava flows, and ashfall; two deaths following 10 August explosion

07/1983 (SEAN 08:07) Eruption continues with ash emission every 10 minutes

08/1988 (SEAN 13:08) Explosions, lava flow

03/1996 (BGVN 21:03) Phreatic explosions, blue gas plumes, crater glow, and dome rockfalls

04/2006 (BGVN 31:04) Some conspicuous plumes during 2004-2005; climber's photos from January 2006

03/2008 (BGVN 33:03) Conspicuous ash plumes, October 2006-December 2007

01/2009 (BGVN 34:01) Thermal anomalies and a minor ash plume during 2008

06/2009 (BGVN 34:06) Occasional ash plume activity continues

01/2010 (BGVN 35:01) Occasional ash plumes and thermal anomalies continue into at least February 2010

02/2011 (BGVN 36:01) Many plumes seen by pilots during past year ending February 2011

02/2014 (BGVN 39:02) Absence of evidence for ongoing eruption; new hazard maps




Bulletin Reports

All information contained in these reports is preliminary and subject to change.


01/1974 (CSLP 09-74) Continuing eruptive activity with frequent explosions

Card 1774 (11 January 1974) Continuing eruptive activity with frequent explosions

"Continual quiet eruption. Much explosive activity. Smoke plume leaves crater every 20-30 minutes. No data about flows or ejecta."

Information Contacts: Minard Hall, Escuela Politécnica Nacional, Quito.

07/1975 (CSLP 50-75) Continued activity; block lava flows and ash emissions

Card 2214 (08 July 1975) Continued activity; block lava flows and ash emissions

The following represents a brief description of the continuing volcanic activity of the almost unknown and inaccesible volcano El Sangay. A scientific group visited the volcano during the week of 24 May to 1 June 1975.

New blocky lava flows, that began before February 1975, continue advancing down the west side of this composite cone. The flows apparently originate in the summit crater (5,160 m) as suggested by the brilliant red glows seen in the crater at night and by occasional small explosions and blasts of dark gray smoke that are quickly dispersed by the high winds. The flows descend to about 3,800 m where they have fanned out and probably cover ~2 km2 in total area. The flow rock appears to be a basaltic andesite with olivine phenocrysts; milky white quartz xenocrysts are notably abundant to the total exclusion of all other types of inclusions.

The summit crater appears to be formed by at least two vents, one of which is emitting white clouds of vapor and sulfurous fumes almost continuously and another which emits infrequent blasts of dark gray clouds. The crater rim was continually being sandblasted by fine volcanic sand and ash, coming from the vents below, but no larger ejecta were observed. The strength of the fumes and the lack of visibility precluded a reconnaissance of the summit vents.

The west side (leeward side) of the volcano is covered by an approximate 70-m-thick sequence of thinly-bedded ashes, which probably corresponds to the renovation of activity in the 1940's after a 15 year dormancy. Since the 1940's the activity has been more Strombolian, marked by very muld but continuous ash eruptions and occasional lava flows. Evidence of past lahar activity is everywhere. The recent activity of El Sangay presents no danger to man.

Information Contacts: Minard Hall, Escuela Politécnica Nacional, Quito.

07/1976 (NSEB 01:10) Explosions, lava flows, and ashfall; two deaths following 10 August explosion

A recent expedition, 28 July-9 August, to the stratovolcano Sangay reports the following activity.

Mild explosive activity occurred at intervals of 6-12 hours with the expulsion of white, vapor-rich, sulfurous plumes that rose approximately 100 m. Very acidic rains were falling W of the cone. The NW side of the cone was covered by still-hot lava flows (basaltic andesite) from the last few years. A new lava flow was leaving the S crater and has descended W several hundred meters. A light coating of ash covered the snow on the SW side of the cone. No other activity was observed on the other sides of the volcano. It appeared that this activity has continued steadily from last year. A small parasitic cone of approximately 50 m height was recently discovered on the lower E flank. It is not presently active.

On 10 August an independent British team, which apparently included no geologist, reached the 3,700 m basecamp level on the volcano. Two days later six members ascended to within 300 m of the summit. At 1230 an explosion produced a black mushroom cloud that reached an estimated 300 m above the volcano and dropped ejecta (to 35 cm) on the group. Later, search parties found three injured, one dead, and another had not been found 5 days after the accident. Helicopter rescue attempts were abandoned on 18 August after two days of heavy snowfall.

Information Contacts: M. Hall, Escuela Politécnica Nacional, Quito; J. Aucott, British Embassy, Quito.

07/1983 (SEAN 08:07) Eruption continues with ash emission every 10 minutes

. . . During overflights on 4 and 6 August, Maurice Krafft observed frequent ash emission from 1 of 4 WSW-ENE-trending vents in the summit area. The westernmost vent was filled by a blocky lava dome 15-20 m in diameter, partially covered by ash. ENE of the dome, explosions at least every 10 minutes from a 15-m-diameter crater produced thick black cauliflower-shaped ash columns 100-300 m high. Winds blew ash from these explosions to the SW, toward the dome. Each explosion also triggered small ash avalanches from deposits on the upper W and SW flanks. The largest of the four vents, ENE of the active crater, was 80-100 m across and contained two fumaroles that were emitting vapor. The fourth vent, 20-30 m in diameter and slightly N of the trend of the other 3 vents, was not active during the overflights.

Minard Hall reported that activity was generally similar when he visited the volcano in 1976. Although lava was oozing from the westernmost vent at that time, it had not yet built a dome.

Information Contacts: M. Krafft, Cernay, France; M. Hall, Escuela Politécnica, Quito.

08/1988 (SEAN 13:08) Explosions, lava flow

Geologists from GEVA visited the volcano in June and August. Throughout June, only summit fumarolic activity was noted, but in early August, explosions every 5 minutes ejected small ash clouds. A warning was issued to aircraft flying in the vicinity of Sangay on 4 August at 2249. On 11 August, a new lava flow extended from the summit ~ 200 m below the crater rim. Blocks from the crumbling flow front rolled down the W and SW flanks to 4,400 m altitude. Larger avalanches from the flow front were observed on 12 August between 1400 and 1500. At 0005 on 13 August, explosions from a S-flank vent covered the volcano's S slope with red-hot lava blocks up to 1 m in diameter. Explosions ejecting blocks and ash continued until 0900. By 1600, the flow had moved to ~ 400 m below the crater rim and numerous blocks fell from the two lobes of the flow front.

Information Contacts: J. Durieux, GEVA, Lyon, France; G. Heiken, LANL, Los Alamos.

03/1996 (BGVN 21:03) Phreatic explosions, blue gas plumes, crater glow, and dome rockfalls

From 24 November to 12 December 1995, the first detailed study of Sangay volcano (figures 1 and 2) was carried out by an Instituto Geofísico/ORSTOM team (Escuela Politécnica Nacional, Quito), with helicopter support from the Ecuadorian Army and the assistance of five local guides from Alao. During this time, activity was characterized by continuous fumarolic steaming, frequent phreatic explosions, occasional crater glow, and dome rockfalls. Previous reports from August 1976, August 1983, and June-August 1988 (SEAN 01:10, 08:07, and 13:08) identified four summit vents aligned WSW-ENE, which are here numbered from 1 to 4 going from W to E.

Figure 1. Present cone of Sangay in December 1995 viewed from the base camp 4.3 km SW. The recent pyroclastic-flow deposit on which the campsite is located is in the foreground, among the badlands corresponding to an older edifice. At the summit can be seen the W lava dome (Vent 1) and its now inactive lava tongues. Photo by M. Monzier, courtesy of ORSTOM.
Figure 2. View of the Sangay summit in December 1995 looking NE from the base camp showing the lava dome and associated lava flows from Vent 1. Behind this dome, a steam plume rises from the main crater (Vent 3). Photo by M. Monzier, courtesy of ORSTOM.

In 1976, Vent 1 consisted of a fracture from which lava was slowly issuing, but by August 1983 it had built a lava dome. This small dome was apparently more active in August 1988, and sent a lava flow 400 m down the W flank, where it split into two lobes. In late 1995 this dome was possibly still growing, and was the source of some fumarolic activity and many rockfalls, making the W and SW slopes of the cone dangerous to cross. Apparently there have been no new lava flows from this vent since August 1988. Vent 2, a small 15-m-diameter crater immediately ENE of Vent 1 has frequently been the site of explosive activity (1976 and 1983), but apparently was less active in 1988 and was quiet during the 1995 visit. The ENE crater (Vent 4) remained inactive but with occasional fumarolic activity.

Vent 3, at 80-100 m across, is the largest and deepest crater. In 1976 and 1983 only fumarolic activity was observed from this crater, but lava was reported in 1988. During the 1995 visit it was the site of frequent phreatic explosions, some separated by hours, others coming as often as every 26 minutes. Several explosions were followed by a rhythmic, pulsating roar that lasted for up to 50 oscillations. White vapor plumes, ejected with the audible explosions, rose several hundred meters above the summit. Light blue gas plumes and occasional red glow at night immediately above this crater implied the presence of lava. Frequent rockfalls from the upper S flank of the cone suggested that some lava may be escaping, breaking off, and rolling down the S slopes.

During the visit a portable MEQ-800 Sprengnether seismograph with a vertical, 1-Hz L4C geophone was operated at the La Playa base camp, 4.3 km SW of the main crater at 3,600 m elevation. A preliminary study of the smoked-paper seismograms showed three types of seismic signals, frequently associated with observed explosions in the crater (figures 3 and 4): tremor, long-period, and hybrid events. Tremor events had a monochromatic signature with a period of 1 second and lasted < 60 seconds. The long-period events had emergent arrivals and a constant period of ~0.7 seconds; they were often associated with observed explosions. Hybrid events began with a long-period event (0.7 seconds) and were followed by a signal similar to that of the tremor (1 second). Some hybrid events were associated with audible and observed explosions followed by a roar like pulsating, rhythmic exhalations. No local high-frequency events were detected.

Figure 3. Types of volcanic earthquakes at Sangay recorded by the seismic station 4.3 km SW in December 1995. Courtesy of ORSTOM.
Figure 4. Volcanic seismicity recorded at Sangay, 26 November-10 December 1995. Courtesy of ORSTOM.

Recent lavas and pyroclastic-flow, debris-flow, and lahar deposits are ubiquitous around the cone and testify to Sangay's nearly continuous activity. The site of the La Playa camp (figure 5) is on an andesitic pyroclastic-flow deposit containing bombs up to 4 m in diameter which was emplaced between 1956 and 1965. An accident with two fatalities happened in August 1976 (SEAN 01:10). A previously unreported accident occurred in December 1993 when the main crater exploded just as two mountaineers looked over its rim. Both were blinded by the heat and fragment impacts and remained lost in the jungle on the cone's lower slopes until rescued three days later.

Figure 5. Preliminary geological/structural map of Sangay volcano based on fieldwork, aerial photographs, and 1:50,000 topographic maps from the Instituto Geografico Militar, Quito. Key: M = metamorphic formations; I, II, III = successive volcanic edifices; C1 and C2 = avalanche calderas; AD = avalanche deposits. Campsites are shown as black dots (La Playa = basecamp, Z = Zumbacocha and D = Duende are secondary camps).

In addition to the present cone (Sangay III), two previous edifices were identified and sampled, both of which had been destroyed by collapse. The remnant calderas are found on the E side of the present cone and are breached E toward the Amazon plain. Their probable avalanche deposits lie at the E foot of the cone. A preliminary geologic map of Sangay (figure 5) shows the three successive edifices and the two associated calderas. Edifice I is mainly built of lava, whereas edifices II and III contain both lava and pyroclastic deposits. The products of edifices I and II appear to be more varied in composition (greater differentiation) than those of Sangay III, where mafic andesites seem to predominate.

This isolated stratovolcano E of the Andean crest is one of Ecuador's most active volcanoes having been in frequent eruption for the past several centuries. The steep-sided glacier-covered volcano towers above the tropical jungle on the E side; on the other sides heavy rains have caused plains of ash to be sculpted into steep-walled canyons up to 600 m deep. The first historical eruption was reported in 1628, and more or less continuous eruptions took place from 1728 until 1916, and again from 1934 to the present.

Information Contacts: M. Monzier and C. Robin, ORSTOM, A.P. 17-11-6596, Quito, Ecuador (Email: monzier@orstom.ecx.ec or robin@orstom.ecx.ec); M. Hall, P. Mothes, and P. Samaniego, Instituto Geofísico, Escuela Politécnica Nacional, A.P. 17-01-2759, Quito, Ecuador (Email: mhall@instgeof.ecx.ec).

04/2006 (BGVN 31:04) Some conspicuous plumes during 2004-2005; climber's photos from January 2006

Our previous report was in 1996 (BGVN 21:03); this report covers the time interval January 2004 to January 2006. According to a 2004 annual summary on the Instituto Geofísico (IG) website, Sangay was one of the most active volcanoes in Ecuador, and has been in eruption for ~ 80 years. Its isolated location (figure 6) has meant it has been thought of as a relatively small hazard risk. For this reason, monitoring has been less than for other Ecuadorian volcanoes. Thermal, visual, and satellite monitoring during 2002-2004 confirmed the central crater as the source of frequent explosions and continuing steam-and-gas emissions.

Figure 6. Satellite imagery showing the region around the city of Riobamba (center) in Ecuador), including Sangay (lower right), Chimborazo (upper left), Tungurahua (upper right), and Licto (center) volcanoes. An eruption plume can be discerned coming from Tungurahua, but the date of the image is unknown. The city of Riobamba is about 50 km NW of Sangay. Courtesy of Google Earth.

During 2004 observers did not see lava flows or pyroclastic flows. An abnormally large eruption cloud was detected on 14 January 2004; it contained dominantly steam and gases, with minor ash content. Although only clearly detected and reported then, such events are thought to occur with considerable frequency.

Ramon and others (2006) summarized Sangay's activity as continuously erupting since 1934. Thermal images taken during the last three years showed that only one of the three summit craters was active and documented a lack of new, visible lava flows.

On 14 January 2004 a plume from Sangay was observed around 0500. The plume extended about 45 km E and most likely contained ash. During this time a hotspot was also visible on the satellite imagery. On 27 January 2004 a narrow ash plume emitted by Sangay rose to 6 km altitude and drifted SW.

On 1 May 2004, based on a pilot's report, the Washington VAAC noted that ash from an eruption at Sangay produced a plume to a height of ~ 6 km altitude at 1750. Ash was not visible on satellite imagery.

On 28 December 2004 around 0715 a plume from Sangay, most likely composed of steam with little ash, was detected. The plume was E of the volcano's summit at a height of ~ 6.4 km altitude. A hotspot was prominent on satellite imagery, but ash was more difficult to distinguish.

On 16 October 2005 around 0645 Sangay emitted an ash plume. The plume moved SSW very slowly, corresponding to a possible height of ~ 6.7 km altitude. By 0900 the plume was too thin to be visible on satellite imagery and thunderstorms developed in the area, further obscuring the ash cloud. Based on information from the IG, on 26 October 2005 the Washington VAAC noted that ash was seen over Sangay at 0758. No ash was visible on satellite imagery.

Climber's photo journal. Climbers Thorsten Boeckel and Martin Rietze created a website briefly describing a trek to Sangay's summit during 4-12 January 2006. Several of their posted photos from that trip appear here (figures 7-10; unfortunately, the photos, which are strikingly beautiful, were generally presented without much geographic context). The team included at least one local guide and was aided by horses. Settlements on the approach and return included the mountain village St. Eduardo, which they described as ~ 50 km S of Riobamba.

Figure 7. A vista of Sangay at nightfall in early January 2006. Direction of view is approximately WNW. Photo credit to Boeckel and Rietze.
Figure 8. Photograph documenting the climbers tent camp high on the snowbound slopes of Sangay during their descent. Exact location on Sangay unknown; this was labeled "day 4/5," and should correspond to 7 or 8 January 2006. Photo credit to Boeckel and Rietze.
Figure 9. A topographic high forming part of the Sangay structure, gently steaming, apparently seen from the summit. This corresponds to 7 or 8 January 2006. Photo credit to Boeckel and Rietze.
Figure 10. A crater on Sangay as seen by the climbers from the summit or upper flanks, described by them as the "snow covered east crater." This photo corresponds to 7 or 8 January 2006. Photo credit to Boeckel and Rietze.

Except for some degassing, the group saw no other activity. Although local residents indicated that the last eruption had occurred about 2 months prior to their visit, intermittent eruptions pose hazards to climbers; in 1976 two climbers were killed by explosions from Sangay (SEAN 01:10).

Reference. Ramón, P., Rivero, D., Böker, F., and Yepes, H., 2006, Thermal monitoring using a portable IR camera: results on Ecuadorian volcanoes in "Cities on Volcanoes IV"; 23-27 January 2006.

Information Contacts: P. Ramón, Instituto Geofísico-Departamento de Geofísica (IG), Escuela Politécnica Nacional, Casilla 17-01-2759, Quito, Ecuador (Email: pramon@igepn.edu.ec); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: http://www.ssd.noaa.gov/VAAC/); Thorsten Boeckel and Martin Rietze, c/o Kermarstr.10, Germerswang, D-82216, Germany (URL: http://www.tboeckel.de/, Email: tboeckel@tboeckel.de).

03/2008 (BGVN 33:03) Conspicuous ash plumes, October 2006-December 2007

Our previous report on Sangay (BGVN 21:03) described occasional, but sometimes conspicuous, steam and/or ash plumes between January 2004 and January 2006. The current report continues coverage of plume emissions through December 2007.

Sangay has continued to erupt, sending ash plumes up to an altitude of about 11 km. A summary of plume activity is indicated in table 1. The information is from the Washington Volcanic Ash Advisory Center (VAAC), and is based on reports from the Guayaquil Meteorologic Watch Office, pilot reports, satellite imagery, and the Instituto Geofísico-Departamento de Geofísica (Escuela Politécnica Nacional). We did not receive any report of activity during the period February 2006 through September 2006, or during the first three months of 2008.

Table 1. Ash plume advisories about Sangay activity, October 2006 through December 2007. Courtesy of the Washington VAAC.

    Date             Altitude (km)     Bearing     Remarks

    11 Oct 2006           2.7             W
    21 Oct 2006           6.7            --
    22 Nov 2006          --             WNW        Hotspot visible on satellite imagery
    02 Dec 2006           8.5            SW
    23 Dec 2006           7.6            --
    01 Jan 2007           5.2            --
    14 Jan 2007           6.1            SW
    28 Jan 2007           6.4            --
    06 Feb 2007           9.1            SW
    06-10 Feb 2007    6.1-9            Several     Hotspot at summit visible on satellite imagery
    13 Feb 2007          --              --        Hotspot at summit visible on satellite imagery
    23 Feb 2007          10.7             S
    25 Feb 2007           6.4            SW
    28 Feb 2007           7.6            --
    02 Mar 2007          --              --        Weak hotspot visible on satellite imagery
    05 Mar 2007       5.2-6.1             W
    12-13 Mar 2007        7               W        Hotspot visible on satellite imagery
    17 Mar 2007           5.2            --        Hotspot visible on satellite imagery
    04 May 2007       5.2-7.6            --
    05 May 2007          --               W        Possible narrow plume on satellite imagery
    24 May 2007           7.3            --
    03 Jul 2007       5.2-7.9             W
    23 Jul 2007           5.5             W        Ash not detected by satellite imagery
    24 Jul 2007           5.2            SW
    28 Jul 2007       6.7-8.2            --        Weak hotspot visible on satellite imagery,
                                                     but ash not detected
    02 Aug 2007           5.5             W        Ash not detected by satellite imagery 
    19 Aug 2007          --              --        Clouds inhibited satellite imagery
    08-09 Sep 2007       --              --        Ash not detected by satellite imagery
    12 Oct 2007           7               W
    26 Dec 2007           6.1            SW
    26-27 Dec 2007       --              --        Thermal anomaly seen on satellite imagery

According to a report from the Instituto Geofísico, activity at Sangay increased at the end of 2006 through the beginning of 2007. They reported that a thermal anomaly was detected by satellite imagery during several days in December 2006. During that time, mountain guides near the volcano observed the fall of incandescent rocks down the volcano's flanks at night and a recent deposit of ash that was sufficiently deep to affect birds, rabbits, and other small animals. The report indicated that the Instituto Geofísico has not installed monitoring instrumentation near Sangay because of a significant logistics problem in maintaining them in this inhospitable area, and also because the area is uninhabited and thus poses no direct human risk. However, the report notes that because ash emissions from Sangay may pose problems for aircraft in the S, SE, and SW parts of the country, the Instituto maintains contact with the civil aviation authority.

Information Contacts: Washington Volcanic Ash Advisory Center, Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: http://www.ssd.noaa.gov/VAAC/); P. Ramón, Instituto Geofísico-Departamento de Geofísica (IG), Escuela Politécnica Nacional, Casilla 17-01-2759, Quito, Ecuador (Email: pramon@igepn.edu.ec).

01/2009 (BGVN 34:01) Thermal anomalies and a minor ash plume during 2008

Ash plumes were reported between October 2006 and December 2007 (BGVN 33:03). Thermal anomalies have been detected between 27 March and 4 December 2008 (table 2). A minor ash plume was seen on satellite imagery and by pilots drifting WNW on 24 September 2008.

Table 2. Thermal anomalies at Sangay based on MODIS-MODVOLC imaging during 1 January to 19 October 2008 (continued from the list in BGVN 33:03). No thermal anomalies were noted in 2008 prior to 27 March. Courtesy of Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts System.

    Date (UTC)     Time (UTC)    Pixels    Satellite

    27 Mar 2008      0320          1         Terra
    08 Apr 2008      0345          1         Terra
    26 Sep 2008      0325          1         Terra
    26 Sep 2008      0625          1         Aqua
    28 Sep 2008      1535          1         Terra
    03 Oct 2008      0630          1         Aqua
    05 Oct 2008      0320          1         Terra
    15 Oct 2008      0355          1         Terra
    15 Oct 2008      0655          1         Aqua
    19 Oct 2008      0330          2         Terra
    13 Nov 2008      0325          1         Terra
    18 Nov 2008      0345          1         Terra
    18 Nov 2008      0645          1         Aqua
    04 Dec 2008      0345          1         Terra

Information Contacts: Washington Volcanic Ash Advisory Center, Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: http://www.ssd.noaa.gov/VAAC/); Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), University of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (http://hotspot.higp.hawaii.edu/).

06/2009 (BGVN 34:06) Occasional ash plume activity continues

Our most recent reports on Sangay noted occasional steam and/or ash plumes between 11 October 2006 and 28 December 2007 (BGVN 33:03) and thermal anomalies between 27 March and 4 December 2008 (BGVN 34:01). The current report continues to tabulate this persistently erupting volcano's plumes from 28 December 2007 to 31 July 2009 (table 3), and thermal anomalies from 4 December 2008 to 10 August 2009 (table 4).

Table 3. Sangay ash plume activity, reported for 29 December 2008 to July 2009. NR signifies not reported and no plumes were observed 29-31 December 2008. TA is thermal anomaly. Courtesy of the Washington Volcanic Ash Advisory Center.

    Date           Maximum     Bearing    Remarks
                   Altitude

    05 Jan 2009     7 km           S 
    09 Feb 2009     7.9           --
    10 Mar 2009     5.5            W      TA detected
    15 Jun 2009     --           WNW      TA reported by VAAC
    26 Jun 2009     7.6            W
    23 Jul 2009     7.9           --

Table 4. Thermal anomalies at Sangay based on MODIS-MODVOLC data during 4 December 2008 to 10 August 2009 (continued from the list in BGVN 34:01). Courtesy HIGP Thermal Alerts System.

    Date (UTC)    Time (UTC)    Pixels    Satellite

    10 Mar 2009     0645          1       Aqua
    10 Aug 2009     0340          1       Terra

Information Contacts: Washington Volcanic Ash Advisory Center, Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: http://www.ssd.noaa.gov/VAAC/); 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://hotspot.higp.hawaii.edu/).

01/2010 (BGVN 35:01) Occasional ash plumes and thermal anomalies continue into at least February 2010

Sangay, which has been in near constant eruption for centuries, continued its eruptive activity into 2010. Previous reports on Sangay (BGVN 33:03, 34:01, and 34:06) had documented occasional ash plumes through 31 July and thermal anomalies through 10 August 2009. After almost two months with no indications of observed by satellite, both plumes and thermal anomalies resumed on 4 October 2009 (tables 5 and 6). Intermittent observations of plumes and MODVOLC thermal alerts were made every month afterwards through February 2010.

Table 5. Sangay ash plumes recorded during August 2009-February 2010. TA indicates a thermal anomaly noted by a VAAC analyst. No plumes were observed during 24 July-3 October 2009. Courtesy of the Washington Volcanic Ash Advisory Center (VAAC).

    Date               Maximum Altitude    Bearing    Remarks

    04 Oct 2009           5.2-7.6 km           W
    15 Oct 2009              --               SW      Seen for ~ 15 km
    16 Nov 2009              --              WNW      TA detected
    01 Dec 2009             7.9 km             W      Eruption reported
    18, 21 Dec 2009         7.9 km             W      TAs detected
    02-03 Jan 2010          7 km              NW      TAs 2-4 January
    14 Jan 2010             7.3 km            --
    02 Feb 2010             8.2 km            --
    22 Feb 2010             7.6 km            --

Table 6. Thermal alerts issued for Sangay by the MODVOLC system during August 2009-February 2010 (continued from the list in BGVN 34:06). Courtesy HIGP Thermal Alerts System.

    Date (UTC)    Time (UTC)    Pixels    Satellite

    04 Oct 2009      0345         1         Terra
    06 Oct 2009      0330         1         Terra
    10 Nov 2009      0700         1         Aqua
    16 Nov 2009      0325         2         Terra
    02 Dec 2009      0325         1         Terra
    21 Dec 2009      0655         1         Aqua
    01 Jan 2010      0640         1         Aqua
    03 Jan 2010      0325         2         Terra
    04 Jan 2010      0710         1         Aqua
    25 Feb 2010      0345         1         Terra

Information Contacts: Washington Volcanic Ash Advisory Center, Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: http://www.ssd.noaa.gov/VAAC/); 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://hotspot.higp.hawaii.edu/).

02/2011 (BGVN 36:01) Many plumes seen by pilots during past year ending February 2011

The last report discussed observations of ash plumes and MODVOLC thermal alerts at Sangay through February 2010 (BGVN 35:01). Intermittent reporting indicated that similar activity continued through at least February 2011, with plumes reaching up to 7.6 km altitude (table 7). Clouds obscured the view at times, and plumes were reported primarily by pilots and were sometimes visible on satellite imagery.

Table 7. Plumes reported at Sangay during April 2010-February 2011. No plumes were noted during March 2011. Courtesy of the Washington VAAC.

DateType of plumeAltitudeDistance
and
direction
Source
21 Apr 2010 Ash 6.7 km - Pilot observation
06 May Ash - - Pilot observation
06 May Ash - W Pilot observation and satellite imagery
22-23 Jul Diffuse plumes - 65-115 km W Pilot observation and satellite imagery
21 and 23 Jul Occasional thermal anomalies - - Satellite imagery
19 Aug Ash-and-gas plumes, intermittent thermal anomalies - 25 km W Satellite imagery
20 Aug Emission - - Pilot observation
30 Aug Ash - - Pilot observation (near Sangay)
05 Sep Ash 5.5 km - Pilot observation
10 Sep Small plume and thermal anomaly - - Satellite imagery
13 Sep Gas with possible ash and a thermal anomaly - W Tegucigalpa Meteorological Watch Office (MWO) (Honduras), pilot observation, and satellite imagery
21 Sep Ash 7.6 km - Pilot observation
06 Oct Small ash clouds - W-NW Pilot observation and satellite imagery
14 Oct Pilot reported ash, only gas plumes drifting NW observed in satellite imagery - NW Pilot observation and satellite imagery
29 Oct Steam and gas plume possibly with ash and a thermal anomaly - - Satellite imagery
05 Dec Ash -   Guayaquil MWO (Ecuador)
12 Jan 2011 Ash and thermal anomaly 6.7 km >45 km SW Pilot observation and satellite imagery
20 Jan Ash 7.6 km - Pilot observation
27 Jan Small ash clouds - N Satellite imagery
23 Feb Pilot reported ash, small cloud drifting NW in satellite imagery with no ash confirmed - SSE Pilot observation and satellite imagery

 

On 5 December 2010, the Washington Volcanic Ash Advisory Center (VAAC) stated that Instituto Geofisico reported elevated seismicity.

The MODVOLC alert system issued thermal alerts for Sangay monthly during March 2010 through early October 2010. Then, alerts were absent until 11 January 2011 (table 8).

Table 8. Thermal alerts issued for Sangay by the MODVOLC system during March 2010-20 March 2011 (continued from the list in BGVN 35:01). The system uses the MODIS instrument on the Terra and Aqua satellites. Courtesy MODVOLC Thermal Alerts System.

Date (UTC)Time
(UTC)
PixelsSatellite
15 Mar 2010 0330 1 Terra
30 Apr 2010 0345 1 Terra
16 May 2010 0345 1 Terra
03 Jun 2010 0330 1 Terra
12 Jul 2010 0340 1 Terra
18 Aug 2010 0655 1 Aqua
28 Sep 2010 0650 2 Aqua
30 Sep 2010 0335 1 Terra
02 Oct 2010 0325 1 Terra
07 Oct 2010 0345 1 Terra
11 Jan 2011 0345 1 Terra
02 Mar 2011 0330 1 Terra

 

Information Contacts: Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: http://www.ssd.noaa.gov/VAAC/); Hawai'i Institute of Geophysics and Planetology (HIGP) MODVOLC 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://hotspot.higp.hawaii.edu/).

02/2014 (BGVN 39:02) Absence of evidence for ongoing eruption; new hazard maps

Previously reported activity from Sangay volcano (figure 11) included ash plumes as late as 23 May 2013 and satellite infrared thermal alerts ending in early May 2013 (BGVN 36:01). In that previous report, satellite thermal alerts from the MODVOLC system were noted to have persisted and as late as 4 May 2013. That lack of alerts continued as late as 16 July 2013 when the MODVOLC website was last checked. Since that reporting, there have been no new updates regarding Sangay on the website of the Instituto Geofisico (IG), the aviation reports have not mentioned Sangay, and other news of Sangay behavior has also been generally lacking.

Figure 11. (Inset at bottom) A regional map showing Sangay with respect to large rivers and other features surrounding Sangay. Orange line is the PanAmerican highway, which passes near Río Bamba on the map's N. Major rivers (blue) are primary routes of lahars. (Main map) A hazards map for Sangay made with hazards focus and compiling the results of multiple kinds of modeling. Key (in Spanish) notes that the upper three colors were based on slope angle (H/L) with text noting gradation of hazards in those regions from pyroclastic flows, lava flows, ash falls, volcanic bombs, rock falls, and proximal lahars. The lower three colors on the key represent inferred gradations of lahar hazard at distance from the volcano. Dashed envelopes in red refer to boundaries for small and moderate sizes of ash falls. White line shows inferred boundary for an E directed debris avalanche. Base map is from the Instituto Geografico Militar (IGM). Taken from an online poster by Ordóñez and others, 2014).

Absence of MODVOLC and aviation alerts does not necessarily translate to a lack of eruptions. The MODVOLC system imposes a reasonably high threshold to the infrared data acquired from space. Factors such as weather conditions, snow pack, and geometry of the vent area may play a role. Emissions of spatter, ash fall, and small pyroclastic flows could easily be missed. Assessments are generally best made in conjunction with information at the volcano. The current eruption began on 8 August 1934 and is thus far confirmed only through 23 May 2013.

Hazard modeling and products. In late 2013 to early 2014 IG released a poster discussing Sangay hazards (Ordóñez and others, 2014), some of the results of which we reprint here (figures 11, 12, and 13). Figure 11 contains IGEPN's recently published a map of volcanic hazards associated with Sangay, which resides in the Cordillera Real between the cities of Río Bamba and Macas. The IG and others have generally considered Sangay one of the most active volcanoes in South America. The poster noted historical records of its eruptive activity dating back to 1628 (Hall, 1977) and in the last century some important periods of activity were recorded during 1903, 1934-1937, 1941-1942, 1975-1976, and 1995 to the present (Monzier et al.. 1999). Observations of surface activity carried out in the past 40 years allowed scientists to recognize some important morphological changes at the summit of the volcano, including the emergence of new craters, dome growth, extrusion of lava flows, local explosions and ash emissions, and relatively small pyroclastic flows.

Figure 12. Modeled ash fall blanket from a hypothetical eruption at Sangay of moderate size. The key (in Spanish) refers to the colors in the key and on the isopach map, with thicknesses in millimeters. Taken from an online poster by Ordóñez and others (2014).
Figure 13. Modeled ash fall blanket from a hypothetical eruption at Sangay of large size. The key (in Spanish) refers to the colors in the key and on the isopach map, with thicknesses in millimeters. Taken from an online poster by Ordóñez and others (2014).

A larger suite of volcanic hazards models is not shown here but includes results VolcFlow. Ash3D, Tephra2, and LAHARZ. The data used for the simulations were obtained from the few geological studies in this volcano (Hall, 1977; Monzier et al, 1999; Johnson et al, 2003). Sangay is judged in some ways analogous to Tungurahua volcano, because of its chemical composition, and it similar lava rheology and eruptive style of volcanic flows.

During August-September 2013, IG installed seismic monitoring instruments (broad band and infrasound ) and for the measurement of sulfur dioxide (SO2) in the southwestern flank of the volcano Sangay. These tools facilitate the monitoring of internal and surface activity of the volcano which will give an early warning of a potential hazards.

With regard to monitoring, during August-September 2013 IG personnel installed ~4 km southwest of Sangay volcano, permanent telemetered monitoring system consisting of a broadband seismic sensor, infrasound, and gas monitoring.

Figures 12 and 13 show the respective modeled results for a moderate and large eruption. To define the zones affected by ash fall, the modeling used the following computer routines based on assumptions and approaches discussed in the literature: Ash3d (Mastin and others, 2012) and Tephra2 (Banadonna and others, 2005). Some input data came from inferences and interpretations of descriptions by Monzier and others (1999) and from analogy with recent eruptions at Tungurahua. Plume heights were assumed to reach 10-15 km in altitude and the magma volumes in the plumes were assumed to be on the order of 0.001-0.005 km3 (dense-rock equivalent, DRE). Wind field data came from the Global Forecast System (NOAA, US National Weather Service, Environment Modeling Center). LAHARZ (Schilling, 1998), a modeling approach, was also taken to estimate the extent and coverage of lahars seen in figure 11. (The poster includes other maps on this topic as well.)

References. Bonadonna, C, Connor CB, Houghton BF, Byrne M, Laing A, Hincks T., 2005, Probabilistic modeling of tephra dispersal: Hazard assessment of a multi-phase eruption at Tarawera, New Zealand; J. Geophys. Res., 110, B03203.

Hall M. (1977). El Volcanismo en Ecuador. Publicación del Instituto Panamericano de Geografía e Historia, Sección nacional del Ecuador, Quito. 120pp.

Mastin, L, Schwaiger H, Denlinger R., 2012, User's Guide to Ash3d: A 3-D Eulerian Atmospheric Tephra Transportation and Dispersion Model, U.S. Geological Survey Open File Report.

Monzier M, Robin C, Samaniego P, Hall M, Cotten J, Mothes P, Arnaud N., 1999, J. Volcanol. Geotherm. Res. 90, 49-79.

Ordóñez J., Vallejo S., Bustillos J., Hall M., Andrade D., Hidalgo S., and Samaniego P., (Document created, December 2013; Accessed online July 2014), Volcan Sangay---Peligros Volcanicos Potenciales, Instituto Geofísico, Escuela Politécnica Nacional (IG-ESPN) (URL: http://www.igepn.edu.ec/volcan-sangay/mapa-de-peligros.html ).

Schilling S. (1998). LAHARZ: GIS programs for automated mapping of lahar-inundation hazard zones. US Geological Survey Open-File Report 98-638; 79 pp.

Information Contacts: Instituto Geofísico-Escuela Politécnica Nacional (IG), Casilla 17-01-2759, Quito, Ecuador (URL: http://www.igepn.edu.ec ); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: http://www.ssd.noaa.gov/VAAC/); and Hawai'i Institute of Geophysics and Planetology (HIGP) MODVOLC 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://hotspot.higp.hawaii.edu/).

The isolated Sangay volcano, located east of the Andean crest, is the southernmost of Ecuador's volcanoes, and its most active. The dominantly andesitic volcano has been in frequent eruption for the past several centuries. The steep-sided, 5230-m-high glacier-covered volcano grew within horseshoe-shaped calderas of two previous edifices, which were destroyed by collapse to the east, producing large debris avalanches that reached the Amazonian lowlands. The modern edifice dates back to at least 14,000 years ago. Sangay towers above the tropical jungle on the east side; on the other sides flat plains of ash from the volcano have been sculpted by heavy rains into steep-walled canyons up to 600 m deep. The earliest report of a historical eruption was in 1628. More or less continuous eruptions were reported from 1728 until 1916, and again from 1934 to the present. The more or less constant eruptive activity has caused frequent changes to the morphology of the summit crater complex.

Summary of Holocene eruption dates and Volcanic Explosivity Indices (VEI).

Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
1934 Aug 8 2013 May 23 Confirmed 3 Historical Observations
1728 Sep 30 ± 30 days 1916 (in or before) Confirmed 3 Historical Observations
1628 Oct Unknown Confirmed 3 Historical Observations

This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.


Synonyms

Sanagay | Sangai | Macas, Volcan de

Cones

Feature Name Feature Type Elevation Latitude Longitude
Verdeloma Stratovolcano
The isolated Sangay volcano towers above tropical jungles east of the Andean crest. Seen here from the NE, it is one of Ecuador's most active volcanoes and has been in frequent eruption during the past several centuries. The steep-sided, glacier-covered volcano has been constructed within the older Verdeloma somma to the south. Historical eruptions were first reported in 1628. More-or-less continuous eruptions took place from 1728 until 1916, and again from 1934 until the present.

Photo by Minard Hall, 1976 (Escuela Politécnica Nacional, Quito).
Activity seen in this August 1976 view of the west flank of Sangay volcano is typical of a long-term eruption that began in 1934. An ash plume rises from one of several summit craters. Much of the dark area on the western flank is a shadow, but a dark lava flow can be seen descending the slopes of the volcano. Frequent explosive eruptions and occasional lava flows have constructed Ecuador's most symmetrical volcano. It rises to over 5200-m altitude above the jungles of the western Amazon basin.

Photo by Jean-Christophe Sabroux, 1976 (courtesy of Minard Hall, Escuela Politécnica Nacional, Quito).
A dark lava flow descends the upper western flank of Sangay volcano in 1976. The lava flow originated from the southernmost of several small craters at Sangay's summit. This frequently cloud-covered volcano is Ecuador's most active. Almost continuous minor explosive activity took place from 1728 until about 1916, and resumed in 1934. Occasional larger eruptions produced detonations heard hundreds of km away.

Photo by Minard Hall, 1976 (Escuela Politécnica Nacional, Quito).
Steam clouds rise above two of three summit craters at Ecuador's Sangay volcano. Continual eruptions since 1934 have frequently modified the morphology of the volcano's summit. At the time of this 1976 view from the east, a lava flow from the southernmost crater (right) was descending the western flank.

Photo by Gordon Armstrong, 1976 (courtesy of Minard Hall, Escuela Politécnica Nacional, Quito).

The following references have all been used during the compilation of data for this volcano, it is not a comprehensive bibliography. Discussion of another volcano or eruption (sometimes far from the one that is the subject of the manuscript) may produce a citation that is not at all apparent from the title.

Hall M L, 1977. El Volcanismo en El Ecuador. Quito: Biblioteca Ecuador, 120 p.

Hall M L, 1987. . (pers. comm.).

Hantke G, Parodi I, 1966. Colombia, Ecuador and Peru. Catalog of Active Volcanoes of the World and Solfatara Fields, Rome: IAVCEI, 19: 1-73.

IAVCEI, 1973-80. Post-Miocene Volcanoes of the World. IAVCEI Data Sheets, Rome: Internatl Assoc Volc Chemistry Earth's Interior..

Johnson J B, Aster R C, Ruiz M C, Malone S D, McChesney P J, Lees J M, Kyle P R, 2003. Interpretation and utility of infrasonic records from erupting volcanoes. J Volc Geotherm Res, 121: 15-63.

Johnson J B, Lees J M, 2000. Plugs and chugs--seismic and acoustic observations of degassing explosions at Karymsky, Russia and Sangay, Ecuador. J Volc Geotherm Res, 101: 67-82.

Monzier M, Robin C, Samaniego P, Hall M L, Cotten J, Mothes P, Arnaud N, 1999. Sangay volcano, Ecuador: structural development, present activity and petrology. J Volc Geotherm Res, 90: 49-79.

Smithsonian Institution-GVN, 1990-. [Monthly event reports]. Bull Global Volc Network, v 15-33.

Volcano Types

Stratovolcano
Caldera(s)

Tectonic Setting

Subduction zone
Continental crust (> 25 km)

Rock Types

Major
Andesite / Basaltic Andesite
Minor
Dacite
Basalt / Picro-Basalt

Population

Within 5 km
Within 10 km
Within 30 km
Within 100 km
231
1,675
15,130
1,355,275

Affiliated Databases

Large Eruptions of Sangay Information about large Quaternary eruptions (VEI >= 4) is cataloged in the Large Magnitude Explosive Volcanic Eruptions (LaMEVE) database of the Volcano Global Risk Identification and Analysis Project (VOGRIPA).
WOVOdat WOVOdat is a database of volcanic unrest; instrumentally and visually recorded changes in seismicity, ground deformation, gas emission, and other parameters from their normal baselines. It is sponsored by the World Organization of Volcano Observatories (WOVO) and presently hosted at the Earth Observatory of Singapore.
EarthChem EarthChem develops and maintains databases, software, and services that support the preservation, discovery, access and analysis of geochemical data, and facilitate their integration with the broad array of other available earth science parameters. EarthChem is operated by a joint team of disciplinary scientists, data scientists, data managers and information technology developers who are part of the NSF-funded data facility Integrated Earth Data Applications (IEDA). IEDA is a collaborative effort of EarthChem and the Marine Geoscience Data System (MGDS).
Smithsonian Collections Search the Smithsonian's NMNH Department of Mineral Sciences collections database. Go to the "Search Rocks and Ores" tab and use the Volcano Name drop-down to find samples.