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Deposition
Definition

Rock Particles that have been picked up and
transported (eroded) to another area will
eventually be deposited in that area
When does it occur?

Deposition occurs when
wind/water slow
down/stop (or ice melts)
Deposition agents

The same erosional agents that moved sediments from
one place to another will act as a depositional agents.





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Wind
Running water
Ice
Gravity
Man
Fast H2O = erosion
Slow H2O = Depostion
Sedimentation

When the carrying power of an erosional agent
decreases, sediment will begin to be deposited,
this is called sedimentation (takes place in lakes
oceans, and still bodies of water)
Deposition Factors

Particle Size
Larger particles settle quicker than the smaller ones,
when carrying power diminishes (velocity)
 Colloidal (extremely small) particles may remain in
suspension longer  will get deposited in the middle
of a lake or ocean where water is not moving.

Sorting Sediments

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When a mixture of sediment sizes settles in a still
medium (air or water)…..sorting takes place.
Graded Bedding  shows vertical sorting.
Cross Bedding

Sediments sorted at random sizes to the horizon
Deposition Factors

Particle Shape
Smooth and round 
Rough and angular 
Faster
Slower
Why?
Less Friction
More Friction
Deposition Factors

Particle Density
Denser 
Faster 
Less Dense  Slower 
At/Near bottom
At/Near Top
Factors that affect
DEPOSITION
 Particle
Size: smaller = slower
 Particle
Shape: more surface area
 Particle
Density: similar size, >D =
= slower
faster 
Sorting of Sediments
 Vertical
 the
Sorting:
roundest, largest, and
densest particles settle at the
bottom of a layer, while flatter,
smaller, less dense particles
settle at the top (landslide,
underwater landslides)
Deposition Factors

Velocity (speed) of erosional agent


Decreasing velocity produces horizontal sorting
Large particles deposited at shore, smaller particles deposited
(carried) farther.
Sorting of Sediments
 Horizontal
 for
Sorting:
example, at the mouth of a
stream, size will decrease away
from the mouth, as the speed
slows enough to deposit smaller
particles; large particle fall right
away (DELTA!)
HORIZONTAL SORTING
Stream enters a large body of water,
the velocity decreases and deposition
occurs
Larger sediments are deposited first
Delta may form
A Simple DELTA
Drainage Patterns of
Watersheds
 Dendritic
 Radial
 Rectangular
 Trellis
Drainage Patterns of
Watersheds
 Dendritic
 Radial
 Rectangular
 Trellis
Drainage Patterns of
Watersheds
 Dendritic
 Radial
 Rectangular
 Trellis
Drainage Patterns of
Watersheds
 Dendritic
 Radial
 Rectangular
 Trellis
Deposition Factors

Glacial Depostion

Breaks the rules

Will deposit sediments of all sizes

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Unsorted, all mixed up
Till – Dropped by glacier
Outwash – deposited by meltwater
Erratics – Very large boulders
Factors that affect
DEPOSITION
 Particle
Size: smaller = slower
 Particle Shape: more surface area
= slower
 Particle Density: similar size, >D =
faster 
 Velocity of transport: > speed =
slower
Erosional/Depositional System

Combines the erosional process, the
transporting agents and the process of
deposition
Energy Relationships

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Potential Energy: Energy
that can be used
Kinetic Energy: Energy
from movement
W and Y: High P.E. Low
K.E.
X and Z: High K.E. low
P.E.
Dynamic Equilibrium of a Stream


Rate of Erosion = Rate of Deposition
Maybe found at the mouth of a river or the
middle of a curve
Downstream changes
Drainage Patterns
p.298
The topographic streams pattern are not necessarily random. They are affected by rocks
and their structures.
Drainage Pattern
Evolution
Old superposed channels cut
across regional structures.
Younger channels follow
predictable paths through easily
eroded valley rocks.
Meandering stream, Phnom Penh, Cambodia
Oxbow lake
Cut bank
Point bar
Fig. 10.12
Water Dynamics
Slap Your Nose Pappi and have a
Great Day