Name: _____________________________
Topic 10: Deposition (p.177 – 189)
(p.177)
Define Deposition: opposite of erosion – when sediment settles out of being transported, usually
when the energy (velocity) of a system decreases.
In deposition the sediments are placed in locations where they may form beds of sedimentary rocks.
What is another term for beds? Layers
Factors Causing Deposition (p.178)
Deposition usually occurs when the velocity of the agent of erosion decreases.
State the relationship between stream velocity and the particle size the stream can carry.
The greater the velocity of a stream, the larger particle size it can carry.
Approximately, how fast does a stream have to flow in order to transport sediment with a
diameter of 0.10 cm? Use p.6 of the ESRT
~50cm/sec
Characteristics of Sediments and Rate of Deposition
Many aspects of the sediment themselves affect how fast they will be
deposited in air or water environments. These factors include:
__Size________
____Shape________ ____Density_________
Describe how size of the particle affects settling rate.
The larger the particle size the faster the settling rate.
Describe how the shape of the particle affects settling rate.
The more round the shape of the particle, the faster the settling rate.
Describe how the density of the particle affects settling rate.
The more dense the particle, the faster the settling rate.
Sorting of Sediments and Deposition (p.179)
What is the difference between sorted sediments and unsorted sediments?
Sorted sediments are organized, usually by size – there is a pattern to how they were deposited.
Unsorted sediments are not organized in any way – there is no pattern.
Make a sketch of graded bedding. – Vertical sorting! Biggest on bottom to smallest on top.
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Name: _____________________________
Topic 10: Deposition (p.177 – 189)
Make a sketch of horizontal bedding. Horizontal sorting. Largest to smallest sediment sizes
going from left to right (or from right to left) depending upon the direction of the stream.
When the velocity of a wind or water erosional system gradually decreases, such as when a stream
flows into the ocean or large body of water , the larger, denser and more rounded sediments settle
out first.
Unsorted Glacial and Mass Movement Deposits
Explain WHY most of New York State is covered by unsorted sediment deposits. Unsorted
sediments are deposited by glaciers. Since most of NYS was covered by a continental ice sheet
during the last ice age, most of NYS is covered by unsorted, glacial deposits.
A Model of an Erosional-Depositional System
Energy Transformations in the Model System (p.180)
What is the relationship between stream velocity, slope and kinetic energy? The greater the slope,
the greater the velocity of the water. The greater the velocity of the water, the greater the kinetic
energy.
Erosion and Deposition in Relation to Energy Changes (p.180) – THIS IS IMPORTANT!
Wherever the kinetic energy of the system is large, EROSION is the dominant process.
Wherever the kinetic energy of the system is small, DEPOSITION is the dominant process.
Thus, erosion occurs in regions of HIGH VELOCITY or high discharge, and deposition occurs in
regions of LOW VELOCITY or low discharge.
Stream velocity is faster at the OUTSIDE of curves, or meanders, and slower on the INSIDE .
Therefore, EROSION usually occurs at the outside of meanders and DEPOSITION occurs at the
inside.
PAY SPECIAL ATTENTION TO FIGURE 10-6 TO HELP UNDERSTAND THIS!
Characteristic Features of the Chief Depositional Agents (p.182)
Deposition by Streams
In the stream course itself sediments are deposited on the INSIDE of meanders where stream
velocity is LOW (slow moving water).
What forms when a stream floods? Flood plains and levees.
A delta usually forms when a stream enters the ocean or a large lake. What could cause a delta not
to form?
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Name: _____________________________
Topic 10: Deposition (p.177 – 189)
Deposition by Glaciers (p.182)
What forms at the edge of a glacier when there is a balance of melting and forward movement
(dynamic equilibrium)? MORAINE – A LARGE PILE OF USORTED SEDIMENTS (TILL).
How does the shape of a drumlin tell us the direction of glacial movement? THE DRUMLIN
ORIENTS ITSELF IN THE DIRECTION THAT THE ICE WAS COMING FROM. THE
BLUNT EDGE OF THE DRUMLIN POINTS TO WHERE THE ICE CAME FROM.
What is a kettle and how are they formed? A DEPRESSION IN THE GROUND LEFT BEHIND
WHEN A LARGE BLOCK OF ICE BROKE OFF A RECEDING GLACIER AND WAS
COVERED WITH SEDIMENT (OUTWASH). AS THE BLOCK OF ICE MELTED AWAY
THE DEPRESSION FORMS.
How does an outwash plain form and how is it different from sediments deposited directly by ice?
OUTWASH IS FORMED BY THE MELTWATER FROM THE EDGE OF A GLACIER. THE
ICE MELTS, THE LIQUID WATER STREAMS OUT AND WILL CARRY MOSTLY SMALL
SEDIMENT AWAY FROM THE GLACIERS EDGE. OUTWASH IS THE SEDIMENT
DEPOSITED BY THE STREAMS OF MELTWATER, SO IT IS SORTED AND ROUNDED
JUST LIKE MOST RIVER DEPOSITS. IT IS VERY DIFFERENT FROM THE UNSORTED
DEPOSITS LEFT BEHIND WHEN PARTICLES SETTLE DIRECTLY OUT OF ICE.
STUDY FIGURE 10-8!
Deposition on Coastlines by Water Waves and Currents (p.183)
If after or during reading this section you realize you forgot what a long shore current is go back to
Topic 9 (p.168 & 169).
What is a barrier island and how are they formed? BARRIER ISLANDS ARE BASICALLY
GIANT SEMI-PERMANENT SAND BARS. THEY ARE SANDY ISLANDS THAT RUN
PARALLEL TO THE SHORE LINE AND PROVIDE PROTECTION TO THE COASTAL
MAINLANDS.
Deposition by Wind (p.184)
How does the shape of a sand dune tell us the direction from which the wind was blowing?
Draw a picture of a sand dune to illustrate this point. THE WIND COMES FROM THE GENTLE
SIDE OF THE SAND DUNE.
Deposition by Mass Movement (p.184)
What are the three general characteristics of sediments deposited by mass movements (avalanches,
rock falls, landslides, etc…)?
UNSORTED, JAGGED & SHARP
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