Rock bursts or blisters developed in orthoquartzitic bedrock

Location: "Hill 575," Carr-Kaminak Lake area, southern Nunavut, Canada; 62° 13' N, 95° 38' W

These are rock bursts or blisters developed in orthoquartzitic bedrock (Hurwitz formation) on a hill that stood as a low island, 575 ft above present sea level, in the post-glacial Tyrrell Sea. The features are above the highest beaches marking marine limit on this hill, as shown on Images 0069 and 0236. Water freezing in sub-horizontal fractures in the bedrock accumulates in such a way as to form ice lenses that lift the rock surface into a dome-like configuration, until it fractures and becomes inclined at an angle so steep that the rock fragments tumble outward. The resulting fractured fragments tumbled to form a ridge around the central depressions left after the ice responsible for the doming melted away. The original photo was taken from an altitude of about 100 m and at the same time as Image 0112, which shows a different view of the same features. The photo taken for Image 0111 shows the feature at the tip of the peninsula in a ground view.

Updated 03/30/2010 AW