Ice Age Floods National Geologic Trail
Ice Age Floods National Geologic Trail
Where the Palouse River meets the Snake River, Lyons Ferry State Park occupies one of the most geologically significant confluences on the Ice Age Floods trail. Tree-shaded green lawns slope to the cooling waters of the Snake and Palouse Rivers at a spot where J Harlen Bretz...
Where the Palouse River meets the Snake River, Lyons Ferry State Park occupies one of the most geologically significant confluences on the Ice Age Floods trail. Tree-shaded green lawns slope to the cooling waters of the Snake and Palouse Rivers at a spot where J Harlen Bretz discovered the giant gravel bars that proved the Snake River once ran backward during flood events. The park sits at the downstream end of Marmes Rockshelter, one of the oldest known sites of human habitation in North America, where 10,000-year-old remains were discovered in the 1960s. The surrounding terrain is classic scabland: basalt cliffs, deep flood-carved channels, and enormous gravel deposits testifying to the multiple flood paths that converged here before continuing westward to Wallula Gap. During the floods, water surging down the Snake from the south met water pouring through the scabland channels from the north, creating a massive zone of turbulence that deposited the gravel bars Bretz found so compelling. The park offers swimming, boating, and fishing in an extraordinary geological setting. It is the kind of place where you can relax on the beach and ponder the unimaginable.
Open year-round, day-use only. Discover Pass required. Located at the confluence of the Snake and Palouse rivers, about 15 miles north of Starbuck, Washington. 168 acres, 52,000 feet of shoreline, boat launches, swimming, picnic.
Lyons Ferry sits at the strategic outlet where Missoula floodwaters that overtopped the Cheney-Palouse scabland tract were funneled into the Snake River. As floodwaters topped the south valley wall of Washtucna Coulee, they exploited a weakened basalt fracture and rapidly cut the Palouse River canyon (the modern Palouse Falls drainage), draining into the Snake at exactly this confluence. The park is therefore at the outlet of one of the major flood-scour systems and on a slack-water terrace where flood gravels and rhythmites are exposed. From the bridge over the Snake, the Palouse canyon's discordance with the modern Palouse River drainage (the river is far too small to have cut its own canyon) is the visible signature of the floods. Active flood-cutting here occurred between 18.2 and 14 ka per the Balbas et al. (2017) chronology.
No site-specific peer-reviewed updates since the broader Cheney-Palouse tract synthesis in Waitt and O'Connor (2021).
The Palouse Falls Chapter (Pullman/Spokane region) is the IAFI affiliation for Lyons Ferry and Palouse Falls. Chapter field trips routinely visit both. IAFI/NPS interpretive panels are in place at the park.
Best April through October. Combine with Palouse Falls State Park 7 miles upstream — the falls are the headwall of the same flood-cut canyon. Avoid summer afternoons (open exposure, heat).
Every site along the trail will receive the full Terrain360 capture treatment: ground-level 360° panoramas, drone aerial imagery, and photogrammetry-based 3D models that visitors can spin in their browser. This page reserves the slots; the imagery flows in as field capture completes.
Ground-level 360° panorama, every step along the feature, captured by Terrain360 field crews.
Drone flyovers reveal the geometry of catastrophe — ripple marks, gravel bars, and scour patterns invisible from the ground.
Photogrammetry and Gaussian-splat models let visitors rotate, measure, and inspect features in detail-page WebGL viewers.