Missoula Floods were one of the greatest sets of geological events in North America. Occurring as many as 40 times during the last ice age, the floods were caused by waters released from ancient Lake Missoula that scoured the Columbia River basin, carved out the Columbia River Gorge, and swept across at least 16,000 square miles of the Pacific Northwest. On this episode of Locus Focus, Portland State University geology professor Scott Burns returns to discuss the effect of the floods on the landscape of the Willamette Valley. He'll also share the incredible story of how geologist J. Harlen Bretz discovered evidence of the floods nearly 100 years ago.