Volcanic eruptions pose a significant threat to life and livelihood across the planet. Since the 1600s, eruptive activity has resulted in over 300,000 deaths. Today, hundreds of millions of people live within 20 km of an active volcano, and even eruptions that do not result in deaths can have severe impacts. Closure of airspace to commercial travel due to the 2010 eruption of Eyjafjallajökull, Iceland, brought economic losses of $200 million per day. Anticipating and tracking eruptive activity is therefore of utmost importance for preventing loss of life and mitigating against economic impacts and damage to infrastructure.
Unlike most other types of geohazards, many volcanic eruptions are presaged by volcanic unrest that can last for hours to years. Unfortunately, it is estimated that up to 45% of the world’s ~1400 Holocene age subaerial volcanoes are unmonitored, meaning that they have no ground-based seismic, gas, or deformation monitoring. Because many forms of unrest can be measured by satellites, including changes in surface temperature, ground deformation, and variations in gas flux, space-based observations are critical for discovering and characterizing volcanic unrest (especially at otherwise unmonitored volcanoes). Even for those volcanoes with ground-based instruments, satellites can provide unique complementary information. For example, during the 2010 eruption of Merapi, Indonesia, frequent satellite radar acquisitions provided critical information about the rate of dome growth, which in turn informed decisions related to evacuations that are credited with saving thousands of lives.
A pilot project aimed at evaluating the utility of remote sensing data for anticipating, detecting, and tracking volcanic eruptions was completed during 2014–2017. The goals of the pilot were:
1) Demonstrate the feasibility of integrated, systematic, and sustained monitoring of Holocene volcanoes using space-based observations.
2) Demonstrate the applicability and superior timeliness of space-based observations to the operational community (including volcano observatories and Volcanic Ash Advisory Centers) for better understanding volcanic activity and reducing the impact of eruptions.
3) Build the capacity for use of space-based data at volcano observatories where the uptake of remote sensing data has traditionally been limited.
Much of the pilot work focused on regional monitoring of volcanoes in Latin America to evaluate and showcase the potential for a global effort. That region was chosen for special emphasis because: 1) the volcanoes are situated in a diversity of environments (from rain forest to high-altitude desert), providing a good test of the capabilities of different types of satellite data in different settings; 2) volcanic activity is abundant, including persistent eruptive activity, discrete eruptions, and unrest without eruption; 3) explosive eruptions that disrupt air travel were likely to occur over the course of the three-year pilot; and 4) volcano observatories and monitoring agencies in Latin American countries would directly benefit from the additional resources made available by the pilot.
The results of the pilot demonstrated that satellite data are critical for identifying volcanoes that may become active in the future, as well as tracking eruptive activity that may impact populations and infrastructure on the ground and in the air. The major lesson learned is that with sufficient access to data and effort provided by partners to process and interpret those data, volcanic activity can be detected and sometimes forecast. This information, when made available to the local volcano observatories tasked with hazards assessment and mitigation, provides critical input to decisions related to alert levels, deployment of ground-based sensors, and protection of people, property, and resources. The volcano pilot demonstrated that remote sensing data influence the operations at volcano observatories, sometimes resulting in actions that would have been implemented without knowledge gained from satellite data. Further, the pilot demonstrated that there are useful data being collected by satellites that are not being exploited by observatories.
Although the ideal volcano monitoring system involves the integration of both ground- and space-based observations, the great expense and limited deployment of ground-based monitoring requires increased satellite observations to promote volcanic disaster risk reduction worldwide. This is the philosophy behind the volcano demonstrator, which aims to expand beyond Latin America to global operational monitoring of volcanic activity from space. Such an evolution can only happen in stages, as it will require building a team to work with the available data and provide training to volcano observatories in the exploitation of those data. This can be achieved by scaling the work of the pilot from regional to global over a period of several years, adding additional partners as necessary. Our vision for this scaling is:
Year 1: Continue working with volcano observatories in Latin America on data analysis and, especially, capacity building, so that the observatories may ultimately process and interpret remote sensing data themselves. Develop partnerships with research institutions around the world who are interested in contributing to a global monitoring effort, perhaps through the auspices of the new International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI) Commission on Volcano Geodesy.
Year 2: Expand operational monitoring efforts to African volcanoes, a number of which are deforming and experiencing eruptions with attendant thermal and gas emissions. Local scientists and volcano monitoring agencies in Africa have little ability to use remote sensing data (and in some countries like Tanzania, there are no volcano observatories), so providing this information, and training local users in the derivation and interpretation of Earth observation imagery, is of critical importance to volcano monitoring efforts.
Years 3–4: Expand operational satellite monitoring of volcanic activity to Indonesia and the Philippines—both countries with abundant volcanic activity but little ability for the uptake of remote sensing. Training can be done in coordination with the U.S. Geological Survey’s Volcano Disaster Assistance Program, which has established contacts in both locations, and by recruiting partners at institutions with active research programs in southeast Asia.
By the fifth year of the demonstrator, operational volcano monitoring from space will be in place for countries that currently lack easy access to, and ability to exploit, satellite data. Efforts will focus attention on nations that lack expertise in remote sensing, and not on the United States, Japan, and Europe, where there is already expertise, and sufficient resources exist. and expertise
The primary data needs for the volcano demonstrator are SAR and very-high-resolution optical data, which are not freely available in most cases. In addition, use of freely available thermal and visible data will continue, especially through existing global monitoring programs, like MODVOLC, VOLCAT, and the ASTER Volcano Archive. There is certainly continued need for these tools, and support for these capabilities from their responsible agencies is vital.
Detailed pilot results
Pilot results had significant impact in understanding of volcanoes in Latin America—not only in how those volcanoes work, but also in how satellite data can aid with prioritizing deployment of limited resources and aid with decision making.
“The USGS Volcano Disaster Assistance Program works with volcano observatories throughout Latin America and has seen firsthand the impact of the CEOS volcano pilot project. The rapid availability of a variety of data types, coupled with outreach done by pilot participants, has aided local volcanologists in assessing volcanic unrest, like that at Chiles-Cerro Negro (Colombia-Ecuador) in 2014, and also in responding to eruptions, including the unheralded explosion of Calbuco, Chile, in 2015. We and our Latin American counterparts are grateful for the commitment of the CEOS member agencies and the volcano pilot team to provide data, products, and expertise, and we hope that these efforts can be expanded in the future.” — John Pallister, Chief, Volcano Disaster Assistance Program, U.S. Geological Survey (USA)
Specific results with respect to high-threat volcanoes in Chile are discussed in: Delgado F., M. E. Pritchard, S. Ebmeier, P. Gonzalez, and L. Lara (2017). Recent unrest (2002–2015) imaged by space geodesy at the highest risk Chilean volcanoes: Villarrica, Llaima, and Calbuco (Southern Andes). Journal of Volcanology and Geothermal Research, doi:10.1016/j.jvolgeores.2017.05.020.
Overall pilot results are summarized in: Pritchard, M.E., J. Biggs, C. Wauthier, E. Sansosti, D.W.D Arnold, F. Delgado, S.K. Ebmeier, S.T. Henderson, K. Stephens, C. Cooper, K. Wnuk, F. Amelung, V. Aguilar, P. Mothes, O. Macedo, L.E. Lara, M.P. Poland, and S. Zoffoli (2018). Towards coordinated regional multi-satellite InSAR volcano observations: Results from the Latin America pilot project. Journal of Applied Volcanology.
Unrest at Chiles-Cerro Negro, Colombia-Ecuador border
In 2014, escalating seismic unrest at the long-dormant Chiles-Cerro Negro volcanic system, on the Colombia-Ecuador border, raised concerns that an eruption might be a possibility, but ground-based monitoring was limited. Space-based radar data revealed that most of the deformation that occurred was related to thrust faulting due to a strong earthquake, after which unrest subsided, suggesting that the earthquake was both triggered by and relieved pressure from deep magma accumulation. These observations and insights aided volcanologists on the ground with their interpretations of the activity.
“The interferograms that no longer showed significant displacements, as well as the descending GPS data values, along with a lowering of the energy levels of the overall seismic events, were fundamental in helping us arrive to the decision to lower the alert level from orange to yellow.” — Patricia Mothes, Geophysicist, Instituto Geofísico (Ecuador)
“The satellite data we have received from CEOS has been very useful, and we thank the space agencies for making it available to us. The data helped us to pinpoint the exact location of the deformation, which we could not do with only a few ground-based points. This helped the emergency managers to know which zone was affected, which is very important. Both the observatory and the local communities have benefitted from the CEOS Pilot project and we hope that it continues in the future.” — Lourdes Narvaes Medina, volcanologist, Observatorio Vulcanologio y Seismologico de Pasto (Colombia)
More information is available in: Ebmeier, S. K., J. R. Elliott, J. M. Nocquet, J. Biggs, P. Mothes, P. Jarrín, M. Yépez, S. Aguaiza, P. Lundgren, and S. V. Samsonov (2016). Shallow earthquake inhibits unrest near Chiles–Cerro Negro volcanoes, Ecuador–Colombian border. Earth and Planetary Science Letters, 450, 283–291, doi:10.1016/j.epsl.2016.06.046.
Post-eruptive inflation of Cordón Caulle, Chile
Following the 2011–2012 eruption of Cordón Caulle, Chile, inflation was detected in InSAR data obtained via the volcano pilot. This inflation occurred in the absence of seismicity and was not tracked by any ground-based means, but the discovery prompted the responsible volcano observatory to install GPS sensors to monitor the activity. The recognition of inflation also prompted agencies that were monitoring thermal and gas emissions to lower the sensitivity of their automated detection thresholds for the volcano.
“These [InSAR] results surprised OVDAS, as the volcano does not have geodetic instrumentation, and will lead to the deployment of the first c[ontinuous] GPS stations over the volcano.” — Luis Lara, Director, Observatorio Volcanológico de los Andes del Sur (OVDAS, Chile)
More information is available in: Delgado, F., M. Pritchard, D. Basualto, J. Lazo, L. Cordova, and L. Lara (2016). Rapid re-inflation following the 2011–2012 rhyodacite eruption at Cordón Caulle volcano (Southern Andes) imaged by InSAR: Evidence for magma reservoir refill. Geophysical Research Letters, 43(18), 9552–9562, doi:10.1002/2016GL070066.
Monitoring deformation and thermal emissions before and during eruptive activity at Sabancaya volcano, Peru, was important for establishing that there was no deformation associated with activity in 2013–2014. Inflation and an increase in surface temperatures were detected in 2015–2017, however, which accompanied accelerated seismic unrest unrest prior to the onset of new eruptive activity in late 2016 and early 2017.
“We use InSAR satellite observations when available along with our ground observations to understand the threat of ongoing eruptions in Sabancaya and determine the level of alertness. As it is known at the moment the volcano is in full eruption, and we need this information of satellite InSAR [to help] us to forecast.” — Ing. Victor Aguilar Puruhuaya, Jefe de Sismología, Instituto Geofísico, Universidad Nacional San Agustin de Arequipa (Perú)
More information is available in: Jay, J. A., F. J. Delgado, J. L. Torres, M. E. Pritchard, O. Macedo, and V. Aguilar (2015). Deformation and seismicity near Sabancaya volcano, southern Peru, from 2002 to 2015. Geophysical Research Letters, 42(8), 2780–2788, doi:10.1002/2015GL063589.
At Masaya, Nicaragua, inflation and increases in thermal emissions in late 2015, which were not detected from the ground, accompanied an increase in eruptive activity at the volcano. In addition, subtle deformation transients have been recognized from InSAR data, providing a window into the characteristics of the volcano’s past, and potentially future, behavior.
“We use these [InSAR] data sets for different purposes. The main ones are: to inform our executive authorities about the findings of the activity at Masaya volcano related to the most recent unrest and that we are not capable to produce by ourselves; to learn ourselves about the behavior of our volcanoes during particular volcanic activities; to help us to better locate our ground monitoring instruments so that we can better capture the volcano activity signal; and to correlate with data sets from other sensors” — Armando Saballos, Dirección Gral. de Geología y Geofísica, INETER (Nicaragua)
More information is available in: Stephens, K. J., S. K. Ebmeier, N. K. Young, and J. Biggs (2017). Transient deformation associated with explosive eruption measured at Masaya volcano (Nicaragua) using Interferometric Synthetic Aperture Radar. Journal of Volcanology and Geothermal Research, doi:10.1016/j.jvolgeores.2017.05.014.
And: Stephens, K.J., and Wauthier, C. (2018). Satellite geodesy captures offset magma supply associated with lava lake appearance at Masaya volcano, Nicaragua. Geophysical Research letters, doi: 10.1002/2017GL076769.
Mike Poland, USGS (co-lead) (firstname.lastname@example.org)
Simona Zoffoli, ASI (co-lead)
Juliet Biggs, University of Bristol
Matt Pritchard, Cornell University
Christelle Wauthier, Pennsylvania State University
Falk Amelung, University of Miami
Eugenio Sansosti, CNR-IREA
Yosuke Aoki, University of Tokya
Susi Ebmeier, University of Leeds
Mike Pavolonis, NOAA
Rick Wessels, USGS