 In the spring, good exposures can also be seen immediately downstream from the Yukon River hydro dam in Whitehorse which was built to extract energy from the cataracts that were the White Horse Rapids.These rapids and the Miles Canyon provided a significant challenge to gold-seekers heading to the Klondike Gold Rush, and also established the upstream terminus for paddle-wheel river boats.This, the Miles Canyon Basalts are the reason for the establishment of the townsite of Closeleigh, eventually the City of Whitehorse.