CompuServe Messages

Kamron, >> The meanders occur in valleys that have been infilled with sediments and sands.I don't remember seeing any rivers creating a meandering pattern in deep rock canyons. << They don't, not directly at least. Downcutting and canyons are indicative of a young, fast-flowing river. Meanders and wide floodplains are indicative of an old, mature river. However, if an old river establishes meanders and floodplain, then the land it flows on is uplifted or tilted, it will start flowing faster and will start downcutting again. My college Earth Sciences text has a picture that illustrates this perfectly. It's a photo of a part of the San Juan River in Utah. It shows the river with wide, sweeping meanders, including one in which the upstream and downstream curves nearly meet and there's an enormous peninsula with a very narrow neck. A perfect meander — except that the riverbed is a canyon that looks to be a couple of hundred feet deep, meanders and all. These formations (meandering canyons) even have a name — they're called entrenched meanders. Jon W.