A Texas Canyon In Three Days: Everything is Bigger (and Faster) in Texas

The AP reports on Canyon Lake Gorge, a new canyon formed in Texas this year and is now being opened to the public. It is a fascinating story, the 80 feet deep canyon having been formed by spillway waters from Canyon Lake during three days in July 2002.

Then the writer says this:

Neither compares to the world's most famous canyon. It took water around 5 million to 6 million years to carve the Grand Canyon, which plunges 6,000 feet at its deepest point and stretches 15 miles at its widest.

The entire tone of the piece is how amazing this gorge is, how big and how rapidly it was formed. My question is, if an 80 feet deep gorge could be formed from a spillway flood in three days, how many days would it take to form a gorge 6000 feet deep? Seventy-five days or 5 million years?

I realize you can't really extrapolate out the figures. Differences in water volume, flow rate, composition of rock, elevation, temperature and too many other variables would have to be factored in. But think about it. A gorge formed over three days, 80 feet deep. Pretty amazing.