Missoula Ice Age Floods

Slide through eleven reconstructed lake stands and watch the 7-phase dam break in real time. Universal app for iPhone and iPad. No accounts, no ads.

About 15,000 years ago, an ice dam across the Clark Fork in northern Idaho impounded a 2,000-square-mile lake that periodically broke loose and rewrote the Pacific Northwest. Missoula Ice Age Floods lets you watch that lake fill, drain, and reshape the landscape — directly on the map, at the elevations the geologic record actually supports.

WHAT YOU CAN DO

• Slide through eleven reconstructed lake stands, from a low 850 m drainage threshold up to the 1,265 m maximum stand. Watch the shoreline trace real contours across western Montana and northern Idaho — the polygons are computed from USGS 10-meter elevation data, not painted by hand.

• Trigger the dam-break cinematic and watch a seven-phase outburst flood unfold: ice-dam failure, the initial surge through the Purcell Trench, the convergence at Wallula Gap, scabland scouring on the Columbia Plateau, fan deposition in the Pasco Basin, and the rhythmite-forming backwater in the Willamette Valley.

• Read the discharge in real time. A speedometer shows peak flows in cubic meters per second and CFS; a hydrograph translates those numbers into "Amazon Rivers" so the scale is intuitive. The lake-level bar drains as the volume leaves.

• Tap any reconstructed stand for a deep-dive card with the evidence, the confidence level, and the primary literature.

• Browse the Evidence Gallery — giant current ripples at Camas Prairie, the rhythmite sections in the Walla Walla and Willamette Valleys, the Wallula Gap constriction, the high-water tide-line on the surrounding mountains. Tap "Show on map" to fly the camera straight to the location.

• Use the Field Guide for Levels, Dam-break phases, Drainage thresholds, and Sources. Every "Show on map" jumps the simulator to that exact configuration.

• Tilt to 3D for terrain-shaded relief, or stay flat for the cartographic read.

WHAT THIS APP IS NOT

This is an interpretive scientific visualization, not a survey-grade reconstruction. Paleo-lake elevations carry uncertainty; the slider snaps onto reconstructed stands, not arbitrary numbers. Every confidence label, citation, and caveat in the app reflects the current peer-reviewed literature. We've cited Pardee, Bretz, Baker, Waitt, O'Connor, Atwater, Smith, and many others — the bibliography is in Settings → Primary sources.

PRIVACY

No accounts. No analytics. No ads. The app does not collect personal data. iOS may show a one-time prompt about location because the Mapbox map component links the system location framework, but the simulator does not request, use, or store your location.

UNIVERSAL APP

Optimized layouts for iPhone (portrait) and iPad (all orientations). One download covers every device on your Apple ID. iOS 17 or later.

CREDITS

Source data: USGS 3DEP DEM and USGS National Hydrography Dataset (public domain). Base map and terrain: Mapbox. Built by Nature Tools — apps that help people see the natural world more clearly.