Like earthquakes, glaciers and volcanism, waterfalls are an instance of geology operating at human time scales, geology in real time, as it were. In Canada’s Jasper National Park, near the British Columbia-Alberta border, the Sunwapta River cuts through a series of limestone ledges. Glacier fed, the Sunwapta carries glacier flour, making it more corrosive.
A waterfall is a look backwards in time; the further down the waterfall gorge you go, the further back in time you are looking. Here the river drop about thirty feet as it enters the gorge.
A footbridge crosses a narrow point in the gorge – you can see the bracing in the lower left hand corner –as the river makes a sharp left hand turn.
At this point the entire river, larger by volume than the Chena River in downtown Fairbanks, flows through an eight foot wide slot.
The first three photos were taken from the bridge at the top of this shot. That much water, packed with silt, has incredible erosive force, and limestone isn’t that hard a rock. This natural form of hydraulic mining causes the waterfall to move upstream over time, leaving a long, steep-walled canyon below.
Most of this erosion has happened since the Athabasca River retreated from Jasper National Park about 200 years ago, demonstrating that waterfalls are geology in real time, changing the planet as we watch.