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14. Lakes, Rivers, and Dunes: painting the landscape

Exotic Terranes

Water, wind, ice, and gravity move loose sediment (sand, gravel, dirt, volcanic ash, and mud) across the surface of the land, producing a wide range of surficial, or surface, deposits. Although these deposits are formed by many of the same processes that create sedimentary rocks, surficial deposits are generally loose and uncemented and are still part of the environment in which they were formed. Beaches, sand dunes, and floodplains of rivers are all familiar examples of surficial deposits, which form a thin layer over much of the state, covering the older bedrock below.

OGDC units: Quaternary river, stream and lake alluvium, alluvial fans, beach and dune deposits, river and coastal terraces, shelf and slope sediments

Age Range: 2 million years ago to now
Rock Types: gravel, sand, silt, clay
Did You Know? The Oregon Dunes between Coos Bay and Florence contain approximately 4.5 billion cubic yards of sand, enough to fill 450 million dump trucks or build 50 billion sand castles.


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