The Niagara Escarpment began to take shape over 450 million years ago as the bed of a tropical sea. During the millions of years that followed, the sediments were compressed into rock, mainly magnesium-rich limestone (dolostone) and shale. The progressive action of glaciers, water flows and the elements caused the more resilient dolostone to weather at different rates than the shale, resulting in the very dramatic land forms that we see today: sea stacks, karst formation caves, deep valleys, scenic waterfalls, rugged hills, and perhaps most remarkable, the spectacular cliffs along the Niagara Escarpment itself.

Learn more about Niagara Escarpment geology:

• Escarpment Geology (Bruce Trail Magazine, Spring 2015) (.pdf, 702.2 KB)
• Bruce Trail Reference: Maps & Trail Guide (section II-6) (hard copy; or pdf with "Full Set of Downloadable Maps")
• Webinar: Ancient Seas, Glaciers and Waterfalls: The Geologic History of the Niagara Escarpment
• Video: Niagara Escarpment – Its Fascinating Geological and Environmental History (from GeoscienceINFO)