Rising more than 600 metres above the surrounding prairies, the Cypress Hills are a striking geological anomaly on the flat plains. The hills climb sharply from the north before gradually dropping back to the plains in the south. Their highest point (1,466 m) is at "Head-of-the-Mountain."
The Cypress Hills are the highest point in Canada between Labrador and the Rocky Mountains. Unlike the Rocky Mountains, the Cypress Hills were not created by the faulting and folding of a geological uplift. The Cypress Hills are an erosional plateau formed by millions of years of sedimentary deposition followed by millions of years of erosion. Today, the Cypress Hills expose a unique cross-section of geological history found nowhere else in western Canada.
The Cypress Hills resemble a giant layer cake composed of many layers of sedimentary rock. Each layer formed at a different time under different conditions.
The youngest formations are located higher in the hills. Sedimentary rocks are made from sediments that are deposited by water and then compressed and cemented into rock. The grain size of the rock indicates the environment where the sediments were deposited. Gravels are deposited only by fast moving streams. Fine clays are deposited in still water. Most formations are predominantly a single rock type with thin interbedded layers of other rock types.
Geological processes slightly elevated the Cypress Hills region over time. The sedimentary layers remained nearly horizontal but the area became a drainage divide. Large rivers originating in the mountains were forced to flow around this divide for millions of years, which lowered the surrounding land and isolated the Cypress Hills as a high plateau.
The hard conglomerate cap was resistant to erosion and protected the softer rock of the underlying formations. This ensured that the area remained a flat-topped upland. The Cypress Hills had essentially developed their present form even before the last ice age.
Download the Cypress Hills Interprovincial Park Geology Fact Sheet for more information.