Between 1999 – 2000, Kiska volcano subsided by up to 7 cm (volume decrease 0.00003 km³). Interferograms spanning 2000 – 2001 suggest that subsidence continued but at a lower rate (maxmimum displacements ~2 cm). During 2004 – 2005, no deformation occured, but in 2005 – 2006 the summit area of the volcano uplifted by 3 – 4 cm (volume increase 0.00001 km³). The volcano then again subsided between 2006 – 2008 by ~3 cm (volume decrease 0.000005 km³). Overall these observations suggest that during times of quiescence, Kiska alternately uplifts and subsided, with a subsidence prevailing in the long term.
Deformation at Kiska volcano is modelled as a point source. This source is located 0.7 – 1 km below the summit, which suggests that deformation occurs due to pressure changes in the shallow hydrothermal system within the edifice. Uplift occurs when there is a heat flux into the self-sealed reservoir, increasing pore fluid pressure. Subsidence occurs when there is failure of the reservoir.