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A river runs through it

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					A river runs through it

Erosion & rivers
River-related vocabulary
 You may recall the following terms.
 A tributary is a small stream that empties into a
  larger river.
 A watershed is the land that water runs off from
  into a river.
 A divide is an elevated region that separate
  watersheds.
 The path a river follows is called the channel.
 The lengthening and branching of a river is called
  headward erosion.
Stream Erosion
                  Rivers form when
                   precipitation exceeds
                   evapotranspiration.
                  The excess water then
                   carries weathered soil and
                   rock away, and forms a
                   gully.
                  This also causes stream
                   piracy, which is when one
                   stream “captures” another
                   and alters its channel.
Channel Erosion
 The edges of a stream are
  called banks.
 The flow of a stream is
  carrying other sediments –
  these are called loads.
 The three types are
  suspended, bed, and
  dissolved loads.
 The movement of these
  loads contributes to the
  erosion of sediments in the
  channel.
Discharge, gradient, and gaps
                  The discharge is the
                   volume of water moved by
                   a stream in a given time.
                  The gradient is the change
                   in elevation of a stream
                   from top to bottom.
                  A gap is a formation of a
                   river through a mountain
                   range, usually by the
                   motion of isostatic
                   adjustments.
River stages
                A young river has a fast
                 headward erosion,
                 forming a V-shaped valley
                 and waterfalls.
                A mature river drains its
                 watershed and usually
                 only erodes its banks
                 when it floods.
                A mature river also bends
                 and curves, and banks
                 along these parts erode
                 faster (these are called
                 meanders). Abandoned
                 meanders are called
                 Oxbow lakes.
River stages
 An older river has a lower
  gradient and lower
  discharge.
 It usually deposits its
  loads along the bank and
  channel, forming a flat
  plain.
 Movement of the earth’s
  crust can rejuvenate a
  river, and increase its
  gradient and/or discharge.
Reading and assignment
 Now read pages 247-251. The following
  vocabulary will appear:
 Tributaries, watershed, divides, channel,
  headward erosion, stream piracy, stream load
  (please also define suspended, bed, and dissolved
  loads), saltation, discharge, gradient,
  headwaters, water gap, wind gap, meanders,
  oxbow lake, rejuvenated.
 Your homework will be to “glossarize” these
  words.

				
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posted:9/17/2012
language:English
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