Transcript Erosion and deposition

Unit 10
Deposition
Deposition
• The process by which sediments are
released or dropped.
• Effects many people- beaches, mines, caves,
flood plains, sedimentary rocks.
• A series of processes that start with
weathering and erosion. Sediments form
beds, or layers that form sedimentary rocks.
• Final deposition occurs in oceans or lakes.
What Causes Deposition
• Speed of stream slows down or stops
moving.
• Speed and size of sediments determine
rate of deposition.
Characteristics of Sediments
and Rates of Deposition
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Size- larger sediments settle first
Shape- more rounded, faster deposited
Density- higher densities settle first
Saturation of Dissolved Minerals- when
a body of water is completely saturated
with sediments, some will start to
precipitate out.
Sorting of Sediments
• Sediments are sorted by size, shape, and
density.
• If a deposit has sediments of similar size it is
called sorted sediments.
• When a mixture of sizes settles out rapidly a
graded bed forms. Small sediments top and
large sediments bottom.
• Horizontal sorting- slow settling, large
sediments first and small after.
Unsorted Glacial and Mass
Movement Deposits
• Glaciers deposit sediments of all sizes
in no particular order.
• Mass movements dump the sediments
all together regardless of size.
Erosion + Deposition in
Relation to Energy
• Kinetic E is large, erosion is dominant.
• Kinetic E is small, deposition is
dominant.
• Erosion- steep slope, high discharge
• Deposition- gently slope, low discharge
• Tributaries increase velocity and
erosion.
Dynamic Equilibrium
• All sediments picked up must be
deposited. The rate of erosion = rate of
deposition by the stream as a whole.
Stream Deposition
• Sediments deposited on the inside of a
meander.
• Flooding produces levees. Most of the
sediments are spread over the flood
plain.
Wind Deposition
• Small sediment (silts and clays) are
deposited evenly over widespread
areas.
• Sand size particles are deposited in
mounds called sand dunes.
• Particles are well rounded due to
abrasion.