Weathering and Landforms Topics

• Introduction
• Weathering
• Gravity Movements
• Streams
  1. Erosion and Sedimenta-
     tion
     
  Erosion
  Transporta-
  tion
  Deposition
  Base Level
  2. Drainage
  Drainage Basins Drainage Systems Water Gaps
  3. Lakes and Floods
• Groundwater
• Shoreline Waves and Currents
• Wind and Ice
• Landforms in Virginia

Streams (Part 2)

Erosion (continued)

Deposition

• Deposition occurs when transported sediments settle to the bottom as stream velocity decreases. 

The Shenandoah River's floodplain is a result of the river's deposition. (Photograph courtesy of the Virginia Division of Geology and Mineral Resources)

The Shenandoah River meanders across its floodplain.  Floodplains are the results of deposition of river sediment.  Note the extensive farming on the fertile floodplain sediments.   

Base Level

• Base level is the lowest level to which a stream can erode.  It is ultimately controlled by sea level. A drop in base level causes the stream to erode lower to a new level.   

Terraces along the New River at Radford. (Photograph by Robert Whisonant)

Terraces along the New River at Radford show the former levels of river erosion and deposition.  The river has cut down to a lower level, leaving behind terraces to mark the former positions of the stream.   Sediment from the New River can be found on all the terraces, in some cases as high as 400 feet above the present river level.  

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