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Dig into Montana Before History: 11K Years of Hunter-Gatherers in the Rockies and Plains by D. H. MacDonald, Ph.D. See our online store book collection.
This stream carries sediment that has weathered from mountains in Alaska.
Click on image for full size
Courtesy of Bruce Molnia, Terra Photographics

Step 2: Sediments on the Move!

If you sneeze into a pile of dust, the little particles fly everywhere. But if you sneeze into a pile of rocks, they will stay put. It takes more force than a sneeze to move those rocks. Winds and water can have enough force to move rocks.

Larger pieces of sediment can be carried in a stronger current, like fast moving water. Very small particles like silt and clay can be carried by even slow current and settle very slowly. They only form layers at the bottom of quiet water areas like lakes, swamps, or lagoons.

The size of the sediment in a clastic sedimentary rock usually relates directly to the energy of the wind and water that they were deposited in. Sediment that can sink to the bottom in a fast moving river must be very large and heavy. Smaller particles are carried away. However, in a calm lake, even very small pieces of sediment are able to settle to the bottom.

Last modified August 25, 2003 by Lisa Gardiner.

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TES XXVI, 3 fall 2010 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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