Volcanoes present potential hazards not only to human life around these features but also to scientists studying them. With the increase usage of unmanned aerial vehicles (UAVs), or drones, scientists now have a powerful tool to better monitor active volcanoes without getting into a dangerous situation. While being safer to use than traditional monitoring, UAVs can also help deliver vital data to better learn about volcanoes that can help better predict eruptions and how they may disrupt travel and other activities.
Among the many benefits, rotary and fixed-wing drones can provide aerial survey around major volcanoes. This includes using optical and thermal imaging capabilities to provide detailed surveys and monitoring for any shifts in volcanic activity. Recently, the German Research Centre for Geosciences (GFZ) in Potsdam carried out a survey over the Santa Maria volcano in Guatemala, where the lava dome, including viscous lava emitted, were observed. Results of this survey demonstrated that the lava dome has two types of active growth and change, something not observed previously, which included slow expansion and extrusion of lava in the dome. Interestingly, the types of cameras allowed the researchers to make measurements that scientists often want without having to deploy equipment on the volcano, including measuring lava flow velocity, movement patterns of the lava dome, and surface temperature of the volcano. This was all done using high resolution stereo photographic equipment. This also allowed a 3D model of the volcano to be made that also included temperature estimates throughout the volcano. The key demonstration is that some of the most dangerous volcanoes could not only be monitored more safely but the data could also be used to predict potential eruptions, as changing properties could be nearly continuously monitored through the deployment of UAVs. This research is similar to an earlier work that also mapped an active volcano using 3D imagery and thermal imaging, demonstrating some similar results.
There have been many other research projects deploying UAVs. This includes using UAVs to monitor active eruptions such as on Mount Etna in Sicily, including measuring the volume of lava flow. In this case, a digital elevation model (DEM) was created using points from optical monitoring that was then used to create a 3D map and volume estimate on how much lava was flowing from an eruption event. This can help monitor the scale and size of eruptions, helping to provide data on how dangerous given volcanic events could be to human life and property. Additionally, it was shown that UAVs are useful for long-term monitoring as volume changes in a volcano. In a study in Indonesia, UAVs were used to monitor and measure volume loss and gained during explosions using photogrammetry measurements. The study demonstrates the importance of structure mapping and long-term monitoring of volcanoes.
While most studies have used UAVs near volcanoes, or even sometimes flying them inside the area of a volcano, other work has also used high altitude fixed-wing UAVs, which flew outside of visible line of sight, to monitor plumes which can disrupt air travel. In the study that was carried out in Guatemala, plume‐detection and measurement was utilized used sensors carried by a UAV, which also captured atmospheric data that could combined with the plume data. Measuring the plumes and potential hazardous ash and tephra enables a safe way to monitor how dangerous plumes could be to air travel. The work demonstrates that multi-scale data, including near and farther away, are needed to better monitor volcanoes, where understanding plumes during an eruption are also critical for safety.
Increasingly over the last decade, UAVs have been utilized to monitor different aspects of volcanoes, including their active states and as they expand their lava domes prior to eruption. Additionally, monitoring plumes can provide a better way to give warning to flights and provide an indication on how dangerous volcanic eruptions could be to air travel. With increasing ways in which volcanoes can be monitored using UAVs, we should begin to learn more about volcanic behavior without having to put people and expensive instruments in potential harm.
 For more on the research that helped mapped the Santa Maria volcano and derived temperature and other properties, see: Zorn, E.U., Walter, T.R., Johnson, J.B., Mania, R., 2020. UAS-based tracking of the Santiaguito Lava Dome, Guatemala. Sci Rep 10, 8644. https://doi.org/10.1038/s41598-020-65386-2.
 For more on an earlier result showing a 3D thermal model of an active volcano using UAVs, see: Wakeford, Z.E., Chmielewska, M., Hole, M.J., Howell, J.A., Jerram, D.A., 2019. Combining thermal imaging with photogrammetry of an active volcano using UAV: an example from Stromboli, Italy. Photogram Rec 34, 445–466. https://doi.org/10.1111/phor.12301.
 For more on using UAVs to provide volumetric measurements for lava, see: De Beni, E., Cantarero, M., Messina, A., 2019. UAVs for volcano monitoring: A new approach applied on an active lava flow on Mt. Etna (Italy), during the 27 February–02 March 2017 eruption. Journal of Volcanology and Geothermal Research 369, 250–262. https://doi.org/10.1016/j.jvolgeores.2018.12.001.
 For more on long-term monitoring of volcanoes using UAVs in Indonesia, see: Darmawan, H., Walter, T.R., Brotopuspito, K.S., Subandriyo, I Gusti Made Agung Nandaka, 2018. Morphological and structural changes at the Merapi lava dome monitored in 2012–15 using unmanned aerial vehicles (UAVs). Journal of Volcanology and Geothermal Research 349, 256–267. https://doi.org/10.1016/j.jvolgeores.2017.11.006.
 For more on monitoring volcanic plumes and more distant monitoring using fixed-wing UAVs, see: Schellenberg, B., Richardson, T., Watson, M., Greatwood, C., Clarke, R., Thomas, R., Wood, K., Freer, J., Thomas, H., Liu, E., Salama, F., Chigna, G., 2019. Remote sensing and identification of volcanic plumes using fixed‐wing UAVs over Volcán de Fuego, Guatemala. J. Field Robotics 36, 1192–1211. https://doi.org/10.1002/rob.21896.