Global Volcanism Program | Image GVP-03081
U.S. Geological Survey scientists monitor deformation on the Three Sisters volcanoes in the central Oregon Cascades, with Middle Sister volcano in the background. Precise leveling that permits detection of minor uplift is one of several monitoring techniques used to forecast eruptions.
Photo by John Ewert, 1985 (U.S. Geological Survey).
This image is made available as a Public Domain Work, but proper attribution is appreciated.