Factors causing Deposition Deposition occurs when the velocity,
or speed of the stream, wind, or other erosional system decreases
or just stops moving.
Slide 4
Factors causing Deposition The amount of time it takes for a
sediment to get deposited is called the rate of deposition. The
faster the rate of deposition, the less time it takes to deposit
the sediment. The slower the rate of deposition, the more time the
deposition takes.
Slide 5
Factors causing Deposition Two major factors affect deposition:
Velocity of the erosional system How fast the stream, wind, glacier
is moving Characteristic of sediment Physical characteristics of
the rock/soil
Slide 6
Velocity of the Erosional System & Rate of Deposition The
faster the stream moves, the larger pieces of sediments the stream
can carry. Use the Relationship of Transported Particle Size to
Water Velocity in the ESRT.
Slide 7
Characteristic of Sediments & Rate of Deposition Many
factors affect how fast the sediments will be deposited in the air
or water. Size Shape Density Saturation of Dissolved Minerals
Slide 8
*Disclaimer* These factors are discussed as if all the other
factors are the same. So when discussing size, we are talking about
two rocks made of the exact same material, density, shape, and
saturation of minerals.
Slide 9
Size Larger objects are deposited (settled/dropped off) first.
Generally larger objects are heavier and sink faster. Clay sized
particles may float in the water forever. Clay floating in water is
muddy/cloudy water.
Slide 10
Shape A round sediment will settle faster than a flat sediment.
A flat sediment has greater resistance, due to friction, to be
deposited.
Slide 11
Density The higher the density the faster it will be deposited.
A more dense object of the same size and shape will have a larger
mass.
Slide 12
Saturation of Dissolved Minerals Evaporation, temperature
changes, or increases in amount of dissolved minerals in a water
body such as a lake, sea, or ocean may result in a saturated
condition. Saturated condition is when no more minerals can be
dissolved into the water. (Saturated=Full) When the water is
saturated, extra minerals precipitate out forming rocks such as
rock salt and dolostone.
Slide 13
Sorting of Sediments and Deposition Sorted Sediments: Layers of
sediments that are similar in size. Unsorted Sediments: Mixed in
size, density, and shape. Graded: Based on density.
Slide 14
Unsorted Glacial and Mass Movement Deposits In a landslide
(mass movement) or with a glacier, the deposited sediments are very
random. There is no pattern to the deposition of the
sediments.
Slide 15
Slide 16
Erosion and Deposition in Relation to Energy Changes When the
amount of energy is large, erosion is dominant. When the amount of
energy is low, deposition is dominant VelocityKinetic Energy
ErosionHigh DepositionLow
Slide 17
Erosion and Deposition in Relation to Energy Changes Erosio n
Deposition SlopeSteepGentle CurveOutsideInside Discharg e HighLow
LocationSourceMouth
Slide 18
Slope ErosionDeposition SteepGentle
Slide 19
Meanders/Curves Erosion Deposition
Slide 20
Discharge ErosionDeposition HighLow
Slide 21
Discharge If more streams or tributaries enter the stream, it
increases the discharge. This would cause the velocity to increase.
Causing erosion to increase and deposition of solid sediments to
decrease.
Slide 22
Location Deposition
Slide 23
Erosional-Depositional Interfaces Meanders Source and Mouth
Changes in slope
Slide 24
Dynamic Equilibrium of an Erosional System Dynamic Equilibrium
means moving balance. The amount of sediments eroded will be the
same amount of sediments deposited.
Slide 25
CHARACTERISTIC FEATURES OF THE CHIEF DEPOSITIONAL AGENTS
Slide 26
Deposition by Streams In the stream itself, the sediments are
deposited on the inside of the meander, where the stream velocity
is slow. When a stream floods and overflows, some sediments are
deposited on the edge of the river called a levee.
Slide 27
Depositions by Streams The high velocity of a flooding stream
will cut a straight path through a meander. Separating the meander,
forming a curved lake. The deposition at the end of a stream is
called a delta.
Slide 28
Deposition by Glaciers At the end of a glacier, the unsorted
piles of debris are called moraines. If a glacier mounds up the
ground into a streamlined oval shape, this is called a drumlin.
Drumlins look like an upside down spoon. Drumlin tails indicate the
direction of former movement, pointing in the direction the glacier
came from.
Slide 29
Slide 30
Deposition by Glaciers Glaciers leave behind depressions called
kettle holes or kettles. If the kettle is deep enough it will be
filled with water and is called a kettle lake.
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Slide 32
Deposition by Glaciers When glaciers melt, the allow sediments
to get deposited by particle size. This feature is called an
outwash plain. Long Island is made of an outwash plain.
Slide 33
Deposition on Coastlines by Water Waves and Currents
Wind-generated ocean or lake waves slow down when they approach the
shore. This creates a beach. A beach can be made of any sediment
that is deposited, but usually it is sand. When a shoreline has a
natural or man- made pier or peninsula, sediments are deposited
facing an oncoming longshore current.
Slide 34
Slide 35
Deposition on Coastlines by Water Waves and Currents The waves
drag sediments away from the shore, depositing them parallel to the
shore line. This creates a sand bar. If the sandbar break the
surface of the water and vegetation grows, it is called a barrier
island.
Slide 36
Deposition by Wind When wind slows down or stops, the sediments
its carrying are dropped. Wind usually carries sand size sediments
and smaller, called dust. Dust is usually carried by wind over a
long distance from a volcanic eruption.
Slide 37
Deposition by Wind Sand deposited by wind in layers or mounds
are called sand dunes. Sand dunes usually have a steep slope on the
side the wind is blowing towards.
Slide 38
Slide 39
Deposition by Mass Movement When an avalanche or other mass
movement hits the ground and stops moving, the sediments are
deposited as a landform on the earths surface. It is usually
composed of unsorted and unlayered sediments.