* If you've been there, you know that the Colorado River runs through it.
* You also know that it rains there.
* You know that it snows there.
* You probably know that as water freezes and turns to ice it expands.
* Freezing rain and freezing snow-melt inside rocks split rocks apart.
* Fractured rock falls.
* Falling rock striking rock fractures rock further.
* Floods move boulders, rock, pebbles, sand, and silt.
* The Colorado River wasn't dammed until the 1930s.
* In the distant past, a large portion of North America was covered by the Laurentide Ice Sheet.
* Geologists know that melting ice sheets sometimes form inland seas.
* Geologists also know that, sometimes these inland seas are held in by rock and earthen 'dams.'
* Should one of these 'dams' rupture, the entire volume of the inland sea will flow through the rupture, carrying everything in its path, downhill, all the way to the ocean.
* Short of Glaciers scouring out solid rock, moving water is the next most powerful way to terra-form.
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Nobody knows the actual age of the Grand Canyon. The following link suggests that it could have taken 70-million years to form. That would place it in the Cretaceous Period, before the Alps existed, before the Sierra Nevada Mountains existed. Before the Rocky Mountains existed. Before the mass extinction of all dinosaurs and 90% of species on Earth.
If you continuously dig, for 70,000,000-years, you end up with a pretty big ditch. All rock debris carried downstream during annul floods.
Our last ICE AGE was 3-million years ago.
https://www.nationalparks.org/connec...you-never-knew