Sea Kayaking The Slate Islands

Explore this unique geological site in Superior Country.

The simplest way to understand a 500-million-year-old geological phenomenon is to drop a pebble into a puddle. The pebble represents a 30-km-wide asteroid that crashed into the earth at the present-day location of the Slate Islands, a Lake Superior archipelago located 12 km offshore from the lakefront town of Terrace Bay, Ontario.

Today’s Slate Islands reflect the doughnut-shaped upwelling of the earth’s crust that formed after impact, just like the splash when the pebble hit the puddle. Ontario Parks recognized this unique geology in designated Slate Islands Provincial Park in 1985.


Perched high on the cliffs of Patterson Island, the Slate Islands Lighthouse has guided mariners for close to a century.

The impact produced bizarre geological features including shatter cones—serrated, pyramid-shaped rock structures and deposits of gold and copper. You need not a geology degree to appreciate the unique surroundings of the Slate Islands. This cluster of more than 20 islands is also home to a remnant herd of woodland caribou, which thrive in the absence of predators and human disturbance. The population rises and falls based on the availability of Usnea—also known as “old man’s beard,” a type of lichen that dangles from the islands’ lush boreal forest.

The Slate Islands are a refuge for woodland caribou, an endangered species in Ontario. It’s possible to observe these reclusive animals at campsites and swimming between the islands.

The Slates are also one of the best places on Lake Superior to observe tough, wizened arctic-alpine vegetation that’s persisted in a cool microclimate since the end of the last Ice Age, 8,000 years ago. Plants such as encrusted saxifrage, butterwort and three-toothed cinquefoil—all common on the Slates—are typically found 1,500 km north in the arctic or at chilly alpine elevations. These plants are hardy—capable of growing in both dry and very wet conditions and tolerant of short growing seasons—but their range on Lake Superior is rapidly diminishing as climate change increases the lake’s average water temperature.


If you’re an angler, you’re in for a treat at the Slate Islands. Sheltered inner channels harbour a healthy population of lake trout, and shallow water means you can easily catch them with simple fishing gear from a sea kayak.

With myriad sheltered channels and a rugged outer coast, renowned lake trout fishing and a heritage lighthouse, the Slate Islands are a paddler’s paradise. Plan on at least four days to explore the Slate Islands by sea kayak; all but the most advanced paddlers should hire a boat shuttle to and from the islands. The geography of the islands makes the inner harbour the ideal site for a base camp. But campsites are abundant and each has its unique appeal, so you may choose to move camp each day. If you’re a novice paddler, you’re best to sign up for a guided trip with an outfitter like Naturally Superior Adventures.

Pondering the Slates’ fascinating geological history beside a driftwood fire.
About Conor Mihell

Conor Mihell is an award-winning environmental and adventure travel writer based in Sault Ste. Marie. Read his work in the Globe and Mail, Explore, Cottage Life, Canoe & Kayak, ON Nature, and other magazines and newspapers. He's been a sea kayak guide on Lake Superior for close to 20 years, and has paddled from Sault Ste. Marie to Thunder Bay. 

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