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The Bonneville Flood was a massive, six-week event that scoured the canyon with a 350-foot-high wall of water moving at 70 mph.
• The flood created unique geological features like whirlpool-eroded alcoves and gravel bars hundreds of feet high.
Most of the rocks underlying the Snake River Plain originated from massive lava flows related to eruptions of the Yellowstone hotspot over many millions of years. Shoshone Falls flows over a 6-million-year-old rhyolite or trachyte lava flow that intersects the weaker basalt layers comprising the surrounding Snake River Plain, creating a natural knickpoint that resists water erosion.
• The flood created unique geological features like whirlpool-eroded alcoves and gravel bars hundreds of feet high.
Most of the rocks underlying the Snake River Plain originated from massive lava flows related to eruptions of the Yellowstone hotspot over many millions of years. Shoshone Falls flows over a 6-million-year-old rhyolite or trachyte lava flow that intersects the weaker basalt layers comprising the surrounding Snake River Plain, creating a natural knickpoint that resists water erosion.