It looks like a matte painting from a vintage sci-fi film: a British Columbia lake covered in massive, colorful polka dots that emerge as the summer heat boils the water away. But behind the alien beauty of Spotted Lake lies one of the most jarring contradictions in North American history.

This episode unpacks how a saline, endorheic alkali lake revered for centuries as a sacred healing site by the Syilx Okanagan Nation was aggressively strip-mined during the First World War to manufacture high explosives. We follow the science of how the spots form, the brutal wartime extraction, decades of private ownership, and the 22-year fight to return the lake to its rightful stewards.

• Why the lake's closed-basin chemistry concentrates magnesium sulfate, calcium sulfate, and even trace silver and titanium into walkable mineral ridges
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