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. Large pieces of sediment, like sand and gravel, are typically deposited in a fast moving river while smaller particles of sediment are carried away. The sediment is tumbled around in the river and eventually each piece becomes rounded like in the rock shown in (B). This sedimentary rock is called conglomerate. It was once the sediment in 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.
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The Fall 2010 issue of The Earth Scientist
, focuses on rocks and minerals, including articles on minerals and mining, the use of minerals in society, and rare earth minerals, and includes 3 posters!
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