During the last Ice Age, the advancing Cordilleran Ice Sheet from Canada dammed rivers in Montana with up to 2,000 feet of glacial ice, creating huge lakes, including the 3,000-square-mile Glacial Lake Missoula, which held over 500 cubic miles of water, about half the volume of Lake Michigan. When rising water broke the ice dams, tremendous floods burst across the land and down the Columbia River, then returned again as the ice dammed the rivers and the lakes rose once more, producing repeated torrents of water and ice through the Columbia Gorge, perhaps as many as 100 deluges over approximately 3500 years, ending just 12,000 years ago. These floods shaped much of the Columbia River Gorge’s rugged beauty by hammering the mountains, causing vast landslides, scouring away soil at elevations up to 1,000 feet, and creating the dramatic escarpment and bluffs seen today. Around Stevenson, the torrent crested up to 600 feet and reached speeds of up to 50 miles per hour in some places, uprooting trees, leveling hill, and sweeping away wildlife.