GEOLOGY & PLANETARY SCIENCE A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z                    HOME ABOUT CATEGORIES SITE MAP COPYRIGHT ADVERTISE CONTACT entire Web this site alluvium Salt River, Arizona. Credit: Sharon Reynolds, Arizona State University Material such as gravel, sand, silt, or clay deposited, mainly near their mouths, by streams and rivers. Alluvium makes rich agricultural soil, and the earliest civilizations originated as farming communities centered on alluvial flood plains. All rivers have some alluvium deposits, but large rivers such as the Mississippi or Amazon have alluvial plains which are several kilometers wide. See also alluvial fan. Related category    • GEOLOGY AND PLANETARY SCIENCE Source: U.S. Geological Survey Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) BACK TO TOP