Chippewa Falls (introduction) — © Dave Spier
At the east end of Lake Superior, Highway 17, the Trans-Canada Highway, crosses the Harmony River on the east side of Batchawana Bay near Harmony Beach. (This is the second bay on Lake Superior north of Sault Ste. Marie.) Just upstream from the bridge, a wayside park provides access to Chippewa Falls, which is actually two cascades 150 feet apart. The original bedrock is 2.7 billion-year-old pink granite, but, at the lower falls, it is still covered with a remnant of a 1.1 billion-year-old lava flow called the Keweenawan basalt that was extruded during the Grenville orogeny. The contact between the two rocks types represents 1.6 billion years of erosion that brought the granite to the surface by the time of the volcanic activity. A lateral fault cuts through both layers on the north side of the present-day lower falls (out of sight in the two opening photos).
The upper falls was created by a vertical diabase dike cutting across the granite. Here the fault displaces the dike by 30 feet upstream on the northwest side of the river. The upper falls can be reached by an 800 foot trail from the parking area although we didn’t have time to try it. Apparently the trail continues another 500 feet upstream to a bed of large boulders. If you were able to travel six miles further upstream, you’d reach the confluence with the Chippewa River.
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reference: Roadside Geology of Ontario — North Shore of Lake Superior by E. G. Pye, 1997, pgs. 130-131
“A plaque erected by the Ontario Motor League highlights Batchawana Bay (at Chippewa Falls) as the mid-point in the longest national highway in the world — the Trans-Canada Highway.” (from the Batchawana Bay PP page )