Overflight thermal imagery of the eruption of the north crater of Mount Young, Semisopochnoi Island, Alaska, 2021

The Alaska Volcano Observatory conducted overflights of the active north crater of Mount Young on Semisopochonoi Island, Alaska, during its eruption in 2021 to capture the volcanic and hydrothermal activity within the vent during (May 30) and between (June 8) ash emissions. Thermal videos were acquired to see through the ash and steam and observe the features within the active crater. Imagery from one of the surveys on June 8, 2021, during a pause in the eruption, was processed with structure-from-motion (SfM) photogrammetric methods to derive a digital elevation model and thermal orthoimage in this data release. The results reveal the water lake and fumarole features within the crater days after it had last erupted.

Helicopter surveys of the crater were conducted by the U.S. Geological Survey on May 30 and June 8, 2021, taking oblique aerial thermal video with a FLIR T1020 camera. The Pathfinder Aviation AS330 helicopter flew orbits around the target region at about 1000 ft above ground level to produce greater than 95% image overlap. Original radiometric files and postprocessed videos are provided. FLIR video from June 8, 2021, was processed into a sequence of false color images, which were then processed in Agisoft Metashape using structure-from-motion methods to produce a high-resolution thermal false-color orthophoto and digital elevation model. Because of the lack of high-precision camera locations or ground control during the survey, the data were georeferenced to control points from the USGS 2019 IfSAR digital elevation model. The digital elevation model and orthophoto have horizontal resolutions of 0.67 m and 0.33 m, respectively, with a large total (vertical and horizontal) error of 14 meters based on the IfSAR control points.