Home | Session 4 | Rivers Pg 1, 2, 3, 4, 5, 6

Rivers

Presented by Ellen Metzger
San Jose State University and BAESI

V. (cont.)

B. Transportation of sediment

1. Sediments, which are formed by weathering of rocks, are classified by size:

   Particle diameter (mm)	Name
   >256	boulder
   256 to 64	cobble
   64 to 4	pebble
   4 to 2	granule
   2 to 1/16	sand
   1/16 to 1/256	silt
   <1/256	clay

2. Rivers transport sediment and ions which are the products of weathering. Different materials are carried in different ways:

   a. Coarsest sediments are transported as bed load.
   
   b. Finest sediments (silt and clay) are transported as suspended load.

   c. Ions are part of the dissolved load (rivers carry products of chemical weathering to the sea; that's why the sea is salty).

3. In general, the steeper the river channel's gradient, the coarser the sediment it can carry (but there are other factors that affect this).
   
   
4. Wither greater distance of transport, particles become:
   
   
   1. Smaller
   2. More rounded
      
      What would be the size and shape of sediments in the headwaters of a river?
      
      Near its mouth?

Top Next Page

updated March 4, 2002

UCMP Home |  What's new |  About UCMP |  History of Life |  Collections |  Subway