Erosion & Deposition
Aim: How are sediments eroded and
deposited?
Objectives
‹ Describe
how streams weather
and erode Earth’s surface
‹ Describe how streams transport
and deposit sediment
What is erosion?
‹ The
movement of weathered
materials
Greatest Force
‹ Gravity
Greatest Agent
‹ Water
Major Agents of Erosion
Ice
Gravity
Water
Waves
Wi d
Wind
1.
1 Running Water
‹
Rivers & Streams
– Smooth, rounded particles
– Sorted & stratified
(layered, horizontally)
– V Shaped Valleys
How do streams transport
materials?
‹
‹
3 different ways
– 1. in solution: dissolved
2 in suspension: smallest particles
– 2.
– 3. as bedload:
bedload: heavy large particles
Sediment Transportation
Streams & Rivers as Agents of
Erosion
Sediments eroded by water
‹ Rounded
‹ SORTED
– all materials are about
the same size
How Streams Move Sediment
3 factors affecting
S
Stream V
Velocity
l i
‰
‰
‰
Gradient –
slope of
the stream
Discharge
– volume
of water
S
Stream
channel
shape
Stream velocity
‹ Velocity
y
increases outside of curve
(eroding)
‹ Slows inside the curve (depositing)
‹ Velocity
slows when entering a large
body (deltas) of water or land
(alluvial fan)
‹ Meander
M
d
Formation
F
ti
Age of Streams
‹
Young Stage
– V-Shaped
V ll
Valley
– Rapids and
Waterfalls
– No Flood
Plain
‹
Mature
‹
– Erosion widens
the valley
– Slope
decreases
– River
meanders
observed
– A FLOOD
PLAIN
develops
Old Age
•Very Wide
Flood Plain
•Land worn
down to flat
surface
•Oxbow Lakes