i have a friend with a degree in geology who used to work at the canyon.<quoted text>
"Inevitably, some of these visitors will turn to a park ranger and ask: "How did the Grand Canyon get formed? Why did this happen here and nowhere else?"
The honest answer is that nobody knows. One hundred and thirty-one years after John Wesley Powell first mapped the Colorado River by riding its 161 rapids in heavy wooden boats, no one can prove how the canyon was formed.
But it is not for lack of trying.
Geologists are puzzle freaks who love nothing more than collecting fragmentary clues -- clumps of gravel, fossilized shells and pollens, the dates that muddy sediments were deposited in dried-up lakes or whole mountain ranges were lifted -- and then trying desperately to figure out how the modern topography before their eyes was produced.
The modern Colorado appears to be a young river that flows out of the Rockies and hits a huge plateau, called the Kaibab Upwarp, which is 50 million to 70 million years old. Instead of being shunted away from this barrier, the river runs right through it. Moreover, when sediments from the river are examined closely, it is clear that the western end of the canyon -- where it flattens out and begins its final run to the Gulf of California -- is many millions of years younger than the eastern part of the river.
To many experts, this difference means that the Grand Canyon could have been cobbled together from ancient river basins that were created during different geologic eras. But if so, when and how were those ancient rivers formed and where did they go? "
she was giving a tour to a group she didn't know was some kind of fundies and started her spiel about these rocks are so old and overly softer rocks so the erosion....blah blah...the group looked a little stricken and finally one of them spoke up and told her that they believed the earth was only 6,000 some yrs old...kinda shut down the rest of the tour for education. she would start " and these raocks are,erm,older..ish. and they are..erm..pretty!
she still laughs about it to this day.