Volcano number:311350
Country:United States
Geodetic measurements?Yes
Deformation observation?Yes
Measurement method(s):InSAR, GPS - campaign
Duration of observation:1992 - 2000, 2003 - 2010
Inferred cause of deformation:Hydrothermal, Magmatic, Uncertain
Characteristics of deformation:

GPS and InSAR measurements show that Fisher caldera has subsided at ~15 mm/yr between 1992 – 2010. Subsidence is modelled equally well by point, sill, and spheroid sources at depths of 4.5 – 7.5 km. The best fitting sill is 7 – 11 km long, 0.7 – 2.0 km wide and strikes N35° – 55º. Subsidence is attributed to cooling and crystallisation of magma intruded prior to the first deformation measurements. An alternative source would be a reduction of pore fluid pressure due to cooling of the hydrothermal system.

Reference:Mann, Dorte, and Freymueller, J., 2003, Volcanic and tectonic deformation on Unimak Island in the Aleutian Arc, Alaska: Journal of Geophysical Research, v. 108, n. 2, p. 1-12.
Reference:Lu, Z., and Dzurisin, D., 2014, InSAR imaging of Aleutian volcanoes: Chichester, UK, Springer-Praxis, 390 p.
Reference:U.S. Geological Survey Alaska Volcano Observatory (AVO) website
Location:-164.43, 54.65

View NE over Fisher caldera with Mount Finch, the most recently active vent at Fisher, in the foreground on the right. Source P. Stelling, U.S. Geological Survey AVO website