Shear wall left behind after an ice jam release event on the Hay River, NWT (Canada), May 6, 2008
Shear walls are left behind when an ice jam releases. The shear line, between the moving and stationary ice, is near vertical and these particular shear walls were several metres high. Although breakup happens in late April or early May, this remnant ice along the banks often does not melt away until early June.
(photo by Chris Krath, UofA River Ice Group: FujiFilm FinePix A820, f/6.3, ISO-100, FL 35 mm, 1/320 sec. exposure)