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Mountain Rapids

The Mountain Rapids are one of a group of four rapids, collectively called the Slave River Rapids. This spectacular section of the Slave River is one of the finest examples of rapids in North America and has been designated as a National Historic Site because of its importance as a transportation obstacle that affected the development of Canada's north. Today, these violent and dangerous rapids have become a tourist destination for expert kayakers and river rafters.

The Slave River discharges over 80 per cent of all of Alberta's combined river flow. June's average monthly discharge at Fitzgerald is a remarkable 6000 cubic metres per second, which is about 11.5 times the flow of the North Saskatchewan River at Edmonton. That’s a lot of water people! Between Fitzgerald and Fort Smith, a distance of 27 kilometres, the Slave River drops 33.2 metres over four sets of rapids: the Cassette, Pelican, and Mountain rapids, and the Rapids of the Drowned. That doesn’t sound to good does it? All four of these rapids are formed by granite ridges of the Canadian Shield which cross the river channel in a northeast/southwest direction.

The Mountain Rapids are immediately east of a long granite strip of land cuts the river channel in half. Before the construction of the portage road on the west side of the river, the other three sets of rapids were bypassed on the east using narrow side-channels. The Mountain Rapids, however, could not be passed on the east, so the Mountain Portage was established at the narrowest neck of the peninsula. Boats were winched to the summit and allowed to slide down the other side until they reached the river.

Most of the granite exposed at the rapids has been smoothed, polished, and marked with stripes, not by the river but by a southward advancing continental glacier over 10,000 years ago. These elongated rounded glacial landforms are called "whalebacks" and their shape indicates the direction of ice flow. The low, rounded ends point in the direction from which the ice came, while the down-ice end is rough and angular where the glacier plucked off blocks of rock as it passed over.

To learn about another important system of rapids in Alberta click here.