Surface Water Stream landscapes, erosion and deposition

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Surface WaterStream landscapes, erosion and
deposition
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The Water Cycle

• Water constantly moves among the oceans, the
  atmosphere and on land. This unending circulation
  of Earths water supply is the water cycle.
• Evaporation- liquid water to water vapor
• Precipitation- water vapor to liquid water
• Infiltration- water absorbed by land (soil,
  cracks in rocks)
• Runoff- water flowing over land

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Erosion

• Erosion is the transport of weathered material
• Caused by water, wind or glaciers.

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Gravity

• The root cause of all erosion
• Materials falling downhill are called Mass
  Movements
• Examples
• Landslides
• Avalanches
• mud flow
• rock fall

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RUNNING WATER

• The most common agent of erosion on Earths
  surface
• Streams or water flowing over the ground pick up
  and move material.
• These particles weather rocks from abrasion

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Stream Formation

• Run-off is the flow of water over the ground
• Run-off results in the formation of streams
• Streams that flow into other streams are called
  tributaries

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Stream velocity

• Velocity is fastest at the top center
• Slowest near the stream bed
• Velocity is fastest at the outside of a turn
• Results in rapid erosion and carves out the
  deepest part of stream

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Meanders

• As a stream flows across the flood plain, it
  meanders, or curves back and forth
• This is caused by erosion over time.

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• Point bar- deposition occurs on the inside of the
  curve where flow slows down
• Cut bank- erosion occurs on the outside of the
  curve where flow is fastest

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Oxbow lakes

• When a meander gets extreme it will erode back on
  itself and form an oxbow lake

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Carrying Capacity

• How much material a stream can carry relates to
  the velocity (speed) of water.
• Particle size
• Higher velocity larger sediment
• can be carried down stream
• As the stream slows, it deposits larger
  particles.

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Page 6 ESRT
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Stream Velocity(see page 6 of ESRT)

• As stream velocity increases, the volume and size
  of sediments being carried increases.

Volume and particle size
Velocity of stream
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Conversely, as stream velocity decreases, the
settling rate increases.
Incoming stream with sediments
Coarse gravel
Finer sand
Finer silt
Finest clay
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STOP!
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River Deposition

• Deposition is the laying down of weathered and
  eroded sediments (bits and pieces of larger rock
  masses).
• Occurs when velocity of the erosional agent
  (water, wind, glaciers) decreases
• Most deposition occurs in bodies of water.

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River deposits

• Deltas - triangular fan shaped deposits that
  develop as a stream or river flows into a larger
  body of water
• Alluvial fans same kind of deposits but on land

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GLACIAL EROSION

• As a large mass of ice (at least 100 ft thick)
  moves downhill, from gravity, it picks up rock
  material.
• The material grinds against and scratches the
  underlying rock.
• This is called abrasion.
• There are two types of glaciers, valley glaciers
  and ice sheets

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• This is a valley glacier, which flows
• like a stream, down hill.

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• Streams cut V-shaped valleys due to downward
  erosion

V
U

• Glaciers cut U-shaped valleys due to sideways
  erosion

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http//www.youtube.com/watch?vFIn0UoeDyVg
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YOSEMITE VALLEY, California
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Deposition by Glaciers

• As a glacier retreats (ice melts), it drops all
  the material in and on it.
• Note the glacier never moves backwards, the
  front just melts back.
• A variety of deposits are left behind, some are
  sorted and some are unsorted.

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GLACIER
animation
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