Okmok volcano, one of the most active volcanoes in the Aleutian Islands, erupted between 12 July and 19 August 2008 and produced a new tephra cone (Ahmanilix) up to 253 m high. A coeruptive deposit thickness map and the posteruptive elevation change rate map are generated for this phreatomagmatic eruption using the new, high‐resolution (2 m) digital elevation model (DEM) time series provided by ArcticDEM. The total dense rock equivalent (DRE) volume over the proximal deposit field classified from the elevation change map is estimated as 0.147 ± 0.001 km3 DRE (bulk volume of 0.453 ± 0.003 km3). Combined with the distal deposit volume derived from field measurements, the total DRE is 0.25 km3 (bulk volume of 0.76 km3). The estimated erosion rate is up to −15 ± 3 m/year along the flanks of Ahmanilix, and the redeposition rate is about 1 ± 0.3 m/year at the base and 6 ± 1 m/year within the center of Ahmanilix. The surface elevation change also reveals a large ground surface collapse that disrupted the old Cone D lava bench, with a total collapse area of 0.15 km2 and a volume of (7.1 ± 0.4) × 10−3 km3. We also produce a coeruptive deformation map from satellite interferometric synthetic aperture radar (InSAR) using topography from both ArcticDEM and the Shuttle Radar Topography Mission (SRTM) and compare the results. Finally, based on historical eruption volumes, the magma supply rate at Okmok is estimated as (1.77 ± 0.1) × 10−3 km3/year.