Seventeen years (1999-2016) of eruptive activity at the Tungurahua andesitic volcano

Organizers:
Silvia Vallejo Vargas¹, Benjamin Bernard¹
Pablo Samaniego², Silvana Hidalgo¹, Patricia Mothes¹, Jean-Luc Le Pennec², Mario Ruiz¹, Patricio Ramon¹, Hugo Yepes¹

¹ IG-EPN, ² IRD
September 28^th to October 1^st, 2019

Tungurahua volcano is one of the most active volcanoes of the Ecuadorian Andes. After ~75 years of quiescence, Tungurahua reactivated in October 1999 and remained active until March 2016. During this time, the volcano experienced low-to-moderate eruptive activity characterized by frequent explosions, local ash dispersal and frequent lahars. However, its pattern of activity changed in 2006, when one subplinian eruption occurred (August 16th) and produced large pyroclastic density currents and regional tephra dispersal. Since then, eruptive activity evolved to short-lived violent Strombolian to Vulcanian episodes followed by smaller explosions and frequent ash emissions (February 2008, May 2010, December 2012, July 2013, February and April 2014, February 2016).

The main goal of this workshop is to commemorate the 20th anniversary of the beginning of this eruption by bringing together volcanologists that have worked or still work on Tungurahua, and more broadly researchers interested in how andesitic volcanoes work.

We seek contributions from different approaches, such as physical volcanology, petrology, geophysics and those interested on the social issues associated with this long-lived eruption period.

UPDATE: You can access the full programme from this location.

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SESSIONS

Session 1: Geological and petrological process
Conveners: Silvana Hidalgo and Pablo Samaniego
(Saturday, September 28^th, 2019. Afternoon)

Tungurahua volcano is an archetypical andesitic stratovolcano located in the Eastern Cordillera of the Ecuadorian arc. It is one of the most active Ecuadorian volcanoes with at least 4 eruptive episodes during historical times (i.e. since the beginning of the Spanish conquest). These eruptions include the 1641, 1773, 1889 and 1916-1918 events. In 1999, just before the Tungurahua reawakening, Hall et al. (1999) published their pioneering work on the eruptive chronology of Tungurahua volcano. Based on this work, Tungurahua was constructed by 3 successive edifices, the younger being the Tungurahua III that was formed during the last 3000 years, after a large sector collapse. During the last two decades, a series of in-depth studies was devoted to improve several aspects of the geological and petrological evolution of this volcano. Among the most important advances, we should mention: (1) a new geochronological dataset that allows to better constraint the main eruptive stages of this volcano and to estimate its eruptive and erosion rates; (2) the efforts to propose a new, high-frequency eruptive chronology for the last 3000 years BP; (3) the new geochemical and petrological data for the last 3 millennia, that allow us to identify the pre-eruptive magmatic process active at Tungurahua.

Session 2: Geophysical Monitoring and Early Warning at Tungurahua
Conveners: Patricia Mothes and Mario Ruiz
(Sunday, September 29^th, 2019. Morning)

Tungurahua volcano in its nearly 20 years of on-off eruptive activity that began in 1999 produced a huge suite of seismic, infrasound, deformation, laharic and gas signals, and as well an important dataset of visual and infrared images. Since 2006, this volcano has a permanent and modern network of broad band seismic and infrasound stations. Real time data streams were used to forecast possible strengthening or decline of volcanic activity. Temporal deployments of geophysical instruments have also contributed to enhance our understanding of volcanic activity. Strong correlations also exist between patterns seen in the geophysical data and surface activity (ash falls and gravitational flows) of the volcano. In this session we invite those who have worked on Tungurahua geophysical data to present the results and perspectives of their investigations. We would also like to explore other avenues of investigation to be made with the existing data bank that could be exploited through collaborative research.

Session 3: Contributions and teachings of volcano-physics in the follow-up of a long-lasting volcanic eruption
Conveners: Jean-Luc Le Pennec and Benjamin Bernard
(Sunday, September 29^th, 2019. Afternoon)

This session aims to present the main results from volcano-physical studies of the Tungurahua 1999-2016 eruption from the ground up. In order to define the volcanic activity, it is critical to obtain qualitative and quantitative data on the eruptive processes. These data are mostly obtained after detailed field work using up-dated acquisition and processing methods. Tungurahua 1999-2016 eruption exhibited almost every volcanic phenomenon including gas and pyroclastic plumes, pyroclastic fallouts and density currents, lava flows and lahars. The study of those phenomena and their deposits allowed to extract eruption source parameters and test numerical models. Based on the results obtained and their comparison with geophysical monitoring data we would like to open a discussion about the eruptive dynamics at Tungurahua that would be useful for long-term hazard assessment and short-term crisis management. This session is also the opportunity to focus on the debated characterization of Strombolian, violent Strombolian, Vulcanian and sub-Plinian eruptive styles at Tungurahua and other andesitic volcanoes worldwide.

Session 4: Hazard and risk assessment and early warning systems
Conveners: Hugo Yepes and Patricio Ramón
(Tuesday, October 1^st, 2019. Morning)

Once the eruptive period in the Tungurahua began in 1999, hazard assessment was aided by a hazard map prepared in 1988 (Hall et al) which was used to discuss with the authorities and the community on the preparedness plans and mitigation activities. With the new information that was acquired afterwards by the IG researchers, this map was reissued in 2002. Later on, with the experience of what happened during the great eruptions in 2006, a new hazard map of Tungurahua was prepared in 2008, accounting for the effects of these eruptions and that map has been used for hazard mitigation up to the present. The first ash falls that occurred with the initial explosive activity of the volcano gave rise to the generation of the first lahars. The IG installed lahars detectors in the Juive and Vazcún ravines, where they most frequently occurred; this way, a first system of early warning for lahars was initiated, with the participation of authorities, vigías and the community. This was the base for the definitive implementation of the Early Warning System that worked successfully in the following years and until the end of the eruption. We will have different presentations that will discuss how the evaluation of the threat of the volcano was carried out and the experiences on the implementation and application of the Tungurahua Early Warning System.

FieldTrips

Leaders: JLL, PR, PH, PM, BB
(Monday, September 30^th)

• First stop, El Salado hotspring: spring water and lahar monitoring, lahar and PDC deposits, effects of the eruption (2005-2008 lahar, 2006 PDC), exposure to volcanic hazards (hotspring, hotels, technical school of Baños, main road)
• Second stop, Los Pájaros: eruptive history (Cantera Las Juntas, lava flows), 2006 PDC deposits, effects of the eruption (Juive Grande)
• Third stop, Achupashal ravine: past and present activity (lahars, dense and dilute PDCs)
• Fourth stop, Palitahua: effects of the 2006 eruption (victims, houses and bridge), vigías of Tungurahua (Jorge Totoy), fallout monitoring system
• Fifth stop, Penipe: Permanent shelters

Each main stop will be ~1h-1h30.

Workshop Fee: 320 USD

The fee includes:

• transportation Quito-Baños-Quito
• 3 nights at Sangay Hotel (Baños) in double rooms
• 3 breakfasts and 3 lunchs at the hotel
• 4 coffebreaks
• boxlunch for the fieldtrip