River%20Erosion

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River Erosion

• Erosion shapes the land in different ways as the
  river moves from its source to its mouth
• Near the source of a river, in the upper course,
  erosion is vertical (downward). This is because
  the water is being pulled downwards by gravity.
  This forms deep V-shaped valleys.
• Near the mouth of a river, in the lower course,
  erosion is lateral (horizontal or sideways). This
  forms a wide river channel.

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Wave Erosion

• Wave erosion occurs when the wind moves over the
  ocean to produce waves and currents which erode
  the adjacent land.
• Wave action is the greatest during storms and the
  least when the weather is calm.
• Abrasion is the grinding and rubbing action of
  water loaded with sand and rock fragments which
  can wear away the surface of rocks. Waves can
  crack rocks by flinging other rocks against them,
  and once a crack has a been formed, it can be
  widened as water and smaller rocks are forced
  into it. Over time, the destructive power of
  water can transform a rocky cliff into rubble.

http//cse.cosm.sc.edu/erth_sci/Coasts/Erode.htm
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Flatrock
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Wave Movement

• Water waves are characterized by their height,
  their length, and their period. The wave height
  is the distance between the trough (lowest part)
  and crest (highest part) of the wave. The wave
  length is the distance between wave crests. The
  wave period is the time for two consecutive
  crests to pass a point.

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Off Shore Supply Boat
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Refraction

• Refraction is the bending of wave fronts as they
  approach the shore.
• When a wave approaches the shore at an angle, the
  near-shore stretch of wave front reaches the
  shallow water first and is, therefore, slowed
  down first.
• This decrease in speed causes the wave front to
  bend or refract because the deeper water portion
  of the wave continues to move at its original
  speed.
• As a result, the waves near shore tend to
  approach the coast nearly head-on while those in
  deeper water continue along their original
  course.
• Wave refraction has its greatest effect on
  irregular shorelines with deep bays and
  projecting headlands.

http//walrus.wr.usgs.gov/infobank/programs/html/s
chool/moviepage/22.01.08.html
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Jaws
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Sea Spit

• A spit is a deposition landform found off coasts.
• A spit is a type of bar or beach that develops
  where a re-entrant occurs, such as at a cove,
  bay, ria, or river mouth. Spits are formed by the
  movement of sediment (typically sand) along a
  shore by a process known as longshore drift.
  Where the direction of the shore turns inland
  (reenters) the longshore current spreads out or
  dissipates. No longer able to carry the full
  load, much of the sediment is dropped. This
  causes a bar to build out from the shore,
  eventually becoming a spit.

http//en.wikipedia.org/wiki/Spit_(landform)
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Long Point located on the north shore of Lake
Erie
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Examples of wave erosion formations

• Sea cliffs form when a rocky shore erodes at
  approximately the same rate throughout an area.
  This results in a steep walled structure. The
  cliff moves landward as the waves attack its
  base.

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Examples of wave erosion formations

• Sea caves form when waves attack weak portions of
  a cliff. The pounding and cutting of the waves on
  the weak rock cause large holes to be cut from
  the cliff. Notice the small sea cave in the
  picture above.

Anthony Island, Trinity Bay
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Examples of wave erosion formations

• Sea arches are formed when waves cut completely
  through a sea cave. This can form a natural arch
  or bridge.

Cape Broyle
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Examples of wave erosion formations

• Sea stacks are formed when sea arches are eroded
  through the center causing its middle to
  collapse. The remaining columns become sea
  stacks. Eventually the stacks are eroded and they
  are barely visible above the water.

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Headland Erosion