Shear walls seen during breakup on the Athabasca River, AB (Canada) after the release of an ice jam, April 20, 2007
This picture shows the remnant ice left behind after an ice jam releases. To give you a sense of scale, those striped poles on the bank were made from 8 foot lengths of 2×6 lumber. I find it especially fascinating how tightly packed the ice floes were in the ice jam – which you can see by looking at the edge of the shear wall. The pressure was so intense that the porosity of the accumulation was nearly zero.
(photo by Faye Hicks, UofA River Ice Group: Nikon E7600, f/3.7, ISO-50, FL 15mm, 1/357 sec. exposure)