ALLUVIAL FANS and DELTAS

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Part 8

• ALLUVIAL FANS and DELTAS

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• Classic alluvial fan. Fans often develop where
  confined channels on steep gradients suddenly
  emerge from their canyons, changing the flow
  regimen sufficiently to stimulate deposition.

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• River deltas are commonly built off a series of
  anastomotic distributary channels, such as that
  shown at lower right

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• The Mississippi and Atchafalaya Rivers have
  deposited enormous deltas over the past 6000
  years Delta 7 being the youngest and 1 the
  oldest.

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• Abandoned distributaries of the Mississippi and
  Atchafalaya Rivers. The Metairie Ridge
  distributary channel, separating lower and upper
  New Orleans, is shown in red

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• Until the construction of jetties in the late
  1870s, sand bars closed off the mouth of the
  Mississippi River each year for as much as 3
  months at a time following high flows.