The highly fractured area on the right side of this 3 May 1980 photo is the renowned N-flank "bulge" of Mount St. Helens. Intense deformation producing northward displacements up to 2.5 m per day and reduction of rock strength by hydrothermal alteration caused the catastrophic collapse of the N flank, triggering the devastating magmatic explosive eruptions of 18 May.

Photo by William Melson, 1980 (Smithsonian Institution).

This image is made available under the Public Domain Dedication CC0 license, but proper attribution is appreciated.

Keywords: crater | cryptodome | ash | deposit

St. Helens