Field expert explains geological history of ancient floodwaters in Montana

The City of Missoula, Montana, held a meeting on May 2, 2025, to discuss the significant geological events surrounding the Glacier Lake Missoula Ice Age Floods. The meeting featured a detailed presentation on the scale and impact of these ancient floods, which shaped the landscape of the region.

The discussion began with an overview of the immense volume of water that once flowed through the area, estimated to have reached depths of 300 feet and speeds of up to 50 miles per hour. The speaker emphasized the need to conceptualize these floods as a massive river system, far larger than any modern river, to understand the geological features left behind.

Key features discussed included the Moses Cooling gravel bar, which spans three miles and rises as high as a 30-story building. The speaker explained how sediment was deposited as floodwaters slowed, forming various geological structures. Notably, large boulders, some weighing over 200 tons, were identified as remnants of icebergs from glaciers that originated in the Canadian Rockies.

The presentation also highlighted the phenomenon of "gulf scribbles," which are sediment deposits found along the Clark Fork and Flathead Rivers. These features illustrate the power of the floodwaters, which could carry materials at speeds of 50 to 60 miles per hour.

As the floods receded, they created vast lakes in areas such as Yakima and Pasco, which took days to drain. The aftermath of these floods caused significant geological changes, including the collapse of saturated hillsides and the formation of the Columbia River Gorge.

The speaker noted that the floodwaters reached as far as Eugene, Oregon, and discussed the evidence of mammoth remains found in the region, suggesting that these animals were caught in the floods. The meeting concluded with a discussion on the ongoing geological research and the importance of understanding these historical events to appreciate the current landscape.

Overall, the meeting served as a platform to educate attendees about the Glacier Lake Missoula Ice Age Floods, emphasizing their historical significance and the lasting impact on the environment. Further studies and explorations are planned to uncover more about this fascinating geological history.