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Topic 9 Deposition
Regents Earth Science
deposition
Is the “dropping” of transported materials Or the processes by which transported materials
are left in new locations
Factors Affecting Deposition
Particle size
Larger particles settle more quickly than smaller particles (if they have the same shape and density)
Colloids remain suspended indefinitely
Particle Size
Set
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ate
Particle Size
Set
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g T
ime
Particle Shape
Particles of the same size and maximum diameter will settle out in this order: round, oval, flat
The more spherical the particle, the faster the settling rate.
As flatness increases, settling time increases.
Remember: A short time is a high rate!
Particle density
The denser the particle, the faster it will settle in particles that have the same size and shape.
The rate at which particles are deposited by a stream is least affected by
1. size and shape of the particles 2. velocity of the stream 3. the stream’s elevation above sea level 4. density of the particles
A mixture of sand, clay, pebbles, and silt, of uniform shape and density, is dropped from a boat into a calm lake. Which material most likely would reach the bottom of the lake first?
1. sand 2. pebbles 3. clay 4. silt
sorting
the separation of particles during deposition
In sediments of mixed sizes, shapes, and densities
Roundest, largest, and densest particles will be at the bottom of each layer.
Smallest, flattest, and least dense will be at the top of each layer.
Vertical sorting
Sorting from top to bottom throughout a layer
Graded bedding
Layers of sediment that are each vertically sorted Usually occurs in shallow, quiet bodies of water or
in the ocean Degree of sorting is usually greater in the bottom
layer than in the top layer
Process of forming graded beds
Graded bedding
Horizontal sorting
The sorting of sediments into layers in which the particles are sorted horizontally, ranging from largest to smallest in the direction of travel of the transporting agent
Horizontal sorting
delta
A deposit formed at the mouth of a river as it empties into a quiet body of water
Named for the Greek letter delta
QuickTime™ and aCinepak decompressor
are needed to see this picture.
Nile Delta
Mississippi Delta
Alluvial fan A deposit of sediment formed where the velocity of a river slows as it
flows out of the mountains onto the flatland Also called a land delta
Sediments deposited by water are
well sorted (either vertically or horizontally) rounded smooth may show graded bedding