Date post: | 29-Jan-2016 |
Category: |
Documents |
Upload: | emery-lambert |
View: | 219 times |
Download: | 0 times |
EROSION-
The transport of weathered materials…
Major Erosive Agents:
Running WaterGLACIERSWINDOCEAN CURRENTS AND
WAVESMASS WASTING (GRAVITY!)
What happens to rainfall when it hits earth????
Some evaporates Some infiltrates the soil and becomes
groundwater Some becomes runoff
What determines if rainwater becomes runoff or groundwater?
Ground Conditions:Saturated vs. unsaturatedVegetation – amount of plantsSlope or Gradient of the Land
When Runoff becomes confined to a channel – Stream Exists
3 factors affecting Stream Velocity
Gradient – slope of the stream
Discharge – volume of water
Stream channel shape
Different streams flow at different velocities (speeds)
WHY?
GRADIENT!
A
C
B
Would a stream flow faster from A to B or from A to C?
Stream Velocity in a Straight ChannelFastest – middle just below surface
Stream Velocity in a Straight Channel
Water flows at different speeds within the same stream.WHY? FRICTIO
NThe water that is in contact with the sides and bottom of the stream channel will be slowed by friction and will therefore move SLOWER.
The velocity changes in the S-shaped curves called MEANDERS. Fastest on the outside of the curve – erosionSlowest on the inside of the curve - deposition
Water flows differently around curves than it does in a straight
line
Because of this, water flows at different speeds within the same
stream.
Moves faster around the outsideMoves slowly around the inside
This means that around the outside of curves, since the
water is moving faster, it will be able to erode larger
particles
The opposite is also true, since the inside of curves are moving slower, some of the
particles the water carries will become too big and will be
deposited.Here’s a picture:
Deposition
ErosionEROSION
DEPOSITION
Cut bank on outside of curve due to higher velocity of water – more erosion
Cut bank on outside of curve
Point Bar on inside of curve
STREAMS CARRY MATERIAL IN …
Solution: dissolved material (includes salts)
Suspension: particles carried in the flow of the water (Clay, silt, sand)
Bed load: particles carried by rolling, bouncing, or dragging along the stream bed (Pebbles, cobbles, boulders)
THE GREATER THE VELOCITY OF A STREAM…
THE LARGER THE SEDIMENT PARTICLES IT CAN CARRY
THE MORE TOTAL SEDIMENTS IT CAN CARRY
Stream Velocity and Carrying Capacity• Fast moving water can carry larger sediments (duh)
The speed at which a stream flows will determine what size sediments it can
carry
Slow Fast
Big
Sm
all
SEDIMENTS ERODED BY RUNNING WATER WILL HAVE THESE CHARACTERISTICS ROUNDED and SMOOTHSORTED AND LAYERED
SEDIMENTS ERODED BY RUNNING WATER WILL BE … SORTED – all materials are
about the same size