This river (A) carries so much sediment that there are places in the middle where islands of sand and gravel poke up above the water. When the sand and gravel is tumbled around in the river it becomes rounded like in the rock shown in (B). This sedimentary rock was once the sediment on the bottom of a river.
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(A) Martin Miller, University of Oregon and (B) Bruce Molnia, Terra Photographics. Both images courtesy of Earth Science World Imagebank.
Last modified January 6, 2004 by Lisa Gardiner.
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