Qualla: Slate Islands

Slate Islands: Introduction

Mon, 23 Feb 2026 00:00:00 GMT

Photo credit Zatoichi26 at en.wikipedia, CC BY-SA 3.0. Roughly 450 million years ago, a meteorite slammed into what is now the northern shore of Lake Superior and blasted a crater 32 kilometers wide. The violence was unimaginable -- rock shattered into breccia, volcanic pipes formed, and shatter cones radiated outward through the bedrock like frozen shockwaves. Today, what remains of that crater is a quiet archipelago of fifteen islands where woodland caribou pick their way along shorelines of twisted rock and lake trout cruise waters so protected that commercial fishing has been banned to preserve one of the last native stocks in Lake Superior. The Slate Islands are a place where deep time and deep water intersect, and where the evidence of cosmic catastrophe has become a sanctuary for life.

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Image: Zatoichi26 at en.wikipedia | CC BY-SA 3.0

Slate Islands: Written in Stone

Mon, 23 Feb 2026 00:00:00 GMT

Photo credit Zatoichi26 (talk), CC BY-SA 3.0. The geological story of the Slate Islands reads like a textbook on planetary violence. The impact crater, roughly 32 kilometers in diameter, dates to the Middle Ordovician period, approximately 450 million years ago. The islands themselves are the eroded remnants of the crater's ...

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Image: Zatoichi26 (talk) | CC BY-SA 3.0

Slate Islands: Caribou on the Edge

Mon, 23 Feb 2026 00:00:00 GMT

Photo credit Zatoichi26, CC BY-SA 3.0. The Slate Islands hold Ontario's largest herd of boreal woodland caribou, and their story is a textbook case of island biogeography. Caribou first reached the islands across winter ice bridges from the mainland, most recently around 1907. They found an archipelago with no moose, ...

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Image: Zatoichi26 | CC BY-SA 3.0

Slate Islands: A Lake Within a Lake

Mon, 23 Feb 2026 00:00:00 GMT

Photo credit Sharon Mollerus, CC BY 2.0. The archipelago consists of two main islands -- Patterson and Mortimer -- along with five smaller islands (McColl, Edmonds, Bowes, Delaute, and Dupuis) and numerous islets. The nearby Leadman Group to the east is often considered part of the chain, adding Leadman, Cape, Spar, and...

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Image: Sharon Mollerus | CC BY 2.0

Slate Islands: Provincial Park at the Edge of Reach

Mon, 23 Feb 2026 00:00:00 GMT

Photo credit P199, CC BY-SA 3.0. In 1985, the Ontario government established the Slate Islands as a natural environment provincial park, protecting the biodiversity and the geological record while limiting development. It is a non-operating park, meaning there are no paved roads, no ranger stations staffed year-...

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Image: P199 | CC BY-SA 3.0