Approximately 23% (2700 km2) of Cape Breton Island consists of a wide variety of glaciated bedrock (meta-carbonates, carbonates, and evaporites) that has the potential for karst development. An additional 1100 km2 of such strata have been inundated by post-glacial sea-level rise. There have been three main episodes of karstification. The Island represents a portion of the tectonically ancient, deep crustal, eroded terrain of the Appalachian Orogen, more recently influenced by the interplay of sea-level change, ice sheet stability, transient ice aquifers, climate change, and isostatic rebound. Lowland karst units are generally characterized by broad-scale, till-covered, thick evaporite sequences. Within this zone are solution trenches near basin boundaries, salt diapirs, and extensive foundering zones due to salt dissolution, which allowed development of karst breccias to depths exceeding 300 m. The presence of local salt springs suggests a process to move saline water up from depth through foundering breccias or hydraulically active faults. This may in part be responsible for submarine trenches developed to depths of –260 m. Mountain flanks incorporate hydraulically active faults, which have deformed evaporite and carbonate sequences along basin margins. The highlands display paleokarst features within marbles, covered with a thin, discontinuous glacial cover.