Moses Coulee, a Washington state wonder, has puzzled geologists for over a century. This massive canyon, carved into solid basalt, stands as a testament to some powerful force. The culprit? The Ice Age Floods, a series of catastrophic deluges that reshaped the landscape. If you’ve ever visited, or even just passed through Moses Coulee, you may not have been aware that this awe-inspiring coulee has been an Ice Age Floods conundrum since the time geologist J Harlen Bretz first noted it in 1922.
The problem? Moses Coulee doesn’t quite fit the picture. As Bretz described it, “The head of Moses Coulee is just north of Grimes Lake. It is an abrupt termination, walled by 100 foot cliffs, identical with the features of channeled scabland which are called abandoned cataracts.” The head of the coulee ends abruptly, lacking any clear connection to the known flood paths.
Theorists proposed a missing link, a path obliterated by the Okanagan Ice Lobe, but no evidence of such a grand passage has ever been found. The mystery has persisted and become more enigmatic as Ice Age Floods research has flourished over the years: what colossal force carved this immense coulee?
A new study by Gombiner and Lesemann (Geology, 2024) offers a radical new hypothesis. They propose a surprising source for flood waters: meltwater trapped beneath the massive Okanagan Ice Lobe glacier.
Imagine the giant Okanagan ice sheet pressing down on the Waterville Plateau. Meltwater pooled in valleys beneath the ice, trapped and pressurized. This water, according to the theory, found a surprising escape route. Flowing through a network of hidden channels, it carved its way across intervening ridges and valleys, eventually funneling into Moses Coulee.
This “tunnel channel network,” as the researchers describe it, explains the unusual path of the water. The channels themselves, carved in basalt, climb slopes and defy normal drainage patterns. These features, along with glacial landforms like eskers, suggest a watery escape route beneath the ice sheet.
The study doesn’t rule out the role of traditional Ice Age Floods. Water from massive glacial lakes might have also contributed to Moses Coulee’s formation by flowing along the eastern edge of the glacier.
This new hypothesis could be a game-changer. It suggests a hidden world of pressurized meltwater sculpting the landscape beneath the ice. While the debate continues, one thing is certain: Moses Coulee remains a captivating enigma, a place where the power of water and ice continues to unfold its secrets.