Lake Missoula was a giant lake that existed a very long time ago, when dinosaurs roamed the Earth. The lake was so big that it could hold more water than all the Great Lakes combined! But the lake didn't last forever. Many years ago, during the last ice age, glaciers started to form in the mountains around the lake. These glaciers trapped huge amounts of water behind them, creating a gigantic pool of water that slowly filled the lake.
Eventually, the pressure from all that water was too much for the ice to handle. It broke through the ice and came rushing out, like a river on steroids. This is called a glacial lake outburst flood, or a GLOF for short. The flood was so powerful that it carved out giant canyons and left behind huge boulders that are still there today!
Lake Missoula was so big that it actually overflowed multiple times, causing many GLOFs. This flooding cycle created one of the most amazing and unique landscapes in North America – and it all came from the power of water!