Today’s Objective:
How do GLACIERS erode and deposit
sediment?
Do Now:
How are sediments
deposited by gravity,
wind, and waves?
Glaciers are thick masses of ice that
form over thousands of years.
There are two types of glaciers1. Valley Glaciers –
ice that flows
between steep rock
walls from a place
near the top of a
mountain valleys
Example – Alaska
2.Ice Sheets ice that covers a
large region where
the climate is
extremely cold.
Example – Antartica
Also associated with glaciers
are icebergs and ice ages.
An ICEBERG is a large
piece of floating ice.
An ICE AGE is a long
period of very cold
climatic conditions
Glaciers erodes in two ways:
 Plucking – frost
action loosens
blocks of rock and
the glacier then
lifts them away.
 Abrasion – the ice
slides over the rocks
like sandpaper.
 As a glacier melts and
deposits sediment, it
drops the sediments in
the reverse order to
which it was picked up.
 Unsorted – Random
 Angular sediments
•U Shaped Valley – ice
carves a wider valley
pushing everything in it’s
way.
•Kettle Lake – small lake
formed when a chunk of
ice becomes dislodged and
then melts.
•Till – unsorted sediments left behind from a
glacier.
•Moraine –
Ridges of till
•Glacial Erratic –
Large boulders dropped
by melting ice.
•Glacial Lake – a lake
formed when the
glacier begins to melt
•Drumlin – an oval
shaped mound of till.
 V shaped Valley
 Sorted – From
large (on bottom)
 Unsorted – random,
to small (on top)
angular fragments
 Rounded Fragments
 U shaped Valley
•Streams generally erode their channels by
lifting loose particles
•The stronger the current, the more erosional
power it has.
• Materials, like sand
and pebbles, are
carried in a stream
and can erode solid
rock by the process
of abrasion.
Streams transport material in three ways:
• In Solution: dissolved minerals, invisible
• In Suspension : carried by a fluid at the same speed
(largest part of streams load)
• bed load : scooting or rolling along the bottom: (too
large for suspension)
the maximum
load a stream
can carry.
•Deposition occurs as streams’ flow slows
•Sediment settles out and causes a process
called sorting.
What size sediment will settle first in the
river? Why?
COPY DIAGRAM
Which factor most likely caused the sediment to be
sorted in the pattern shown?
*Velocity of the river slows down causing this
pattern of deposition.*
Dynamic Equilibrium
•Stream velocity varies within a stream channel.
•Maximum velocity occurs on the outside of channel
bends; minimum velocity occurs on the inside of
bends.
Depth
Copy diagram A-A’
A
Distance
A’
Straight Section
•Stream bed is
symmetrical
•Highest speed in direct
center
Depth
Copy diagram B-B’
B
Distance
B’
Left Meander
• Stream bed is steeper on
the left and gentle on
the right
• Highest speed in the
center of the deepest
location
Depth
Copy diagram C-C’
C
Distance
C’
Right Meander
• Stream bed is steeper on
the right and gentle on
the left
• Highest speed in the
center of the deepest
location
Label the diagram with an “E”
where erosion is occurring and
a “D” where deposition is
occurring.
Direction
Of
Water Flow
D
E
E
D
D
E
Stream Erosion & Deposition
A
1)At what letters does
erosion occur at?
A and D
B
2) At what letters
does deposition
occur at?
B and C
C
D
•A narrow V-shaped valley
shows that the stream’s
primary work has been down
cutting toward the base level.
•Most predominate features
are rapids and waterfalls.
•A wide valley is created when a river erodes the
banks of its stream channel.
•This side to side cutting creates a flat valley floor,
or a floodplain.
• Most erosion occurs on
the outside of the bank.
• When deposition cuts off
these outside banks an
oxbow lake is formed.
A triangular tract of sediment
deposited at the mouth of a
river
Sediments are
deposited
largest
particles first . . .
smallest particles stay
suspended
A fan shaped deposit forms
on the land when a stream
deposits some of its load.