Global Volcanism Program | Image GVP-12793
The Santa Ana crater lake is in the smallest and deepest of several nested craters across the summit that formed during successive explosive events, seen here in 2011 from the western side on the terrace level. The acid sulfate-chloride lake has a pH around 1, with an associated subsurface hydrothermal system that releases gases into the water.
Photo by Lis Gallant, 2011.
This image is made available under the Public Domain Dedication CC0 license, but proper attribution is appreciated.