1. Erosion and Deposition

2. Vocabulary
Erosion – the process by which weathered rock and soil particles are moved from one place to another. There are 5 types of erosion Deposition – the process by which sediments are laid down in new locations.

3. What is an Erosion/Depositional System?
It is the combination of erosional processes and the process of deposition.
On a worldly scale erosion will equal deposition. This is known as Dynamic Equilibrium.

4. The transfer of rock and soil down slope due to gravity
#1:Gravity: also called
Mass Movement-Wasting
The transfer of rock and soil down slope due to gravity

5. What causes Mass Movement?
Water – Heavy rains or melting snow over saturates the surrounding surface materials with water
Oversteepend Slope: When the steepness of the land exceeds a stable angle, it becomes more likely that material will move down slope.
Earthquakes: Earthquakes shake large areas of land which dislodges large amounts of rock, which are then free to move down hill
Removal of vegetation: Plants keep slopes stable because their roots hold together the soil.

6. Rapid Examples:
Landslide : weakening of rocks/soil/vegetation due to heavy rain.
Mudflow: Weakening of just soil
Rock Slide: weakening of rocks
Avalanche: weakening of snow
** All of these have the power to move millions of tons of material very quickly

7. Slump – another rapid type
Slump – another rapid type. Occurs when a block of rock or soil on the face of a slope slips down so that its upper surface is tilted backwards (rotates).

8. Slow Examples:
Earth flow – slow, caused by heavy rains, where a mass of soil and plant life slowly slides down a slope.
Soil Creep: slowest, caused by alternating periods of freezing and thawing, animal activity, or water movement. Particles move slowly downhill.

9. # 2: Wind
Wind – the most active agent of erosion in deserts, plowed fields and beaches.
Types of wind erosion
Deflation – fine particles are carried high up into the air.
Abrasion – larger particles roll or bounce along the ground.

10. small light particles**
Wind erosion occurs more in deserts because the sediments are dry and lighter than in humid regions where sediments are wet and heavier.
**Wind can only pick up
small light particles**

11. The amount of wind erosion is
dependent on:
size of the particles
speed of the wind
length of time the wind blows
resistance of the rocks.
An oasis forms when the wind erodes the desert until it reaches the depth where water is present allowing grass and trees to grow.

12. Sand dunes – a mound of sand deposited by wind.
They protect the area on the side of the dune away from the ocean from further erosion, small plants often grow here. Can vary in size and shape
The side facing the wind has a gentle slope (windward side), The top (crest), The other side (slip face) is very steep.
Crest
Slip Face
Windward Side

13. Loess are very fine particles of sand and silt that is deposited far away from where it originated.. deflation. Loess deposits are very fertile

14. #3 RUNNING WATER

15. # 3: Running Water Running water – the #1 cause of erosion. Rain can:
Evaporate
Sink into the ground
Flow over the land as runoff

16. 3 factors affecting runoff
1. Amount of rainfall
2. Amount of plant growth in an area
3. The shape of the land: steep slopes = more runoff because it moves too fast to soak into the ground.

17. River Formation
1. Runoff: clay, sand, and gravel are pulled down by gravity& it runs off the land
2. Rills: Water and sediment cut into soil forming tiny grooves
3. Gullies: rills grow wider and deeper & form tiny stream valleys. These act as channels for future runoff.

18. Stream then river: When several gullies come together, a large stream forms.
Drainage System: all the rills, gullies, streams and rivers in an area
Tributaries: Large streams that flow into the main river.
Drainage Basin: The area drained by a main river and its channels… a HUGE area

19. Erosional Power
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.

20. 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)
Capacity-
the maximum load a stream can carry.

21. Immature River
Immature river is V-shaped, steep shorelines, waters flow very quickly, waterfalls & rapids

22. Mature River
Wide U-shape river bottom, gentle slope of shoreline, slow, no rapids/waterfalls, contains meanders, natural levees & wide floodplains

23. DEPOSITION
Sediment settles out and causes a
process called sorting.

24. ** Erosion occurs on the outside of meanders
** Deposition occurs on the inside of meanders

25. River Formations 1. Oxbow lakes: cut off meander
2. Alluvial fans: sediments from a river are dropped on the land forming a fan shape 3. Deltas: sediments from a river are dropped into water (Mississippi Delta)

26. #4 Glaciers

27. Glaciers
Glacier – a large mass of moving ice and snow. Forms where there are many large snowfalls and the temp remains very cold.
Two kinds of glaciers, valley (alpine) and continental, named for location
Glacial ice erodes by abrasion and by plucking away at the rock beneath it. One of the most powerful agents of erosion.
May carry large boulders as well as smaller particles of rock.

28. Deposits by Glaciers
Till – rocks and soil deposited directly by a glacier. Particles vary in size from large boulders to fine clay. Not sorted at all.
Moraines – formed when a glacier melts and retreats leaving a ridge of till.
Lateral moraine – till deposited along the sides of a glacier.
Terminal moraine – till deposited at the front end of a glacier.

29. Glacier deposits continued…
Drumlins – an oval-shaped mound of till. Its tip points in the direction the glacier was moving.
Melt water – streams formed by melting ice.
Outwash plains – sediments deposited by rivers of melt water; fan-shaped; usually in front of terminal moraines, fertile land.

30. Still more…
Iceberg deposits – when parts of the glaciers break off and drift into the sea.
Glacial lakes – when the holes left by glaciers fill with water. Examples: The Great Lakes, The Finger Lakes in New York.
Kettle lakes –block of glacial ice is left behind and melts to form a deep round hole that fills with the water from melting.

31. Striations left in rock from glacier sliding over

32. #5 Wave Erosion

33. The beach will erode during the winter and build up in the summer.
Wave Erosion
The powerful force of
waves constantly erodes
and shapes the shoreline.
Under normal conditions,
waves erode about 1 to 1.5 meters per year. During storms it is increased and can erode up to 25 meters per day.
The beach will erode during the winter and build up in the summer.

34. Sea cliffs- a steep vertical face of rock .
Terrace – when a sea cliff erodes it’s the flat platform left behind.
Sea stack – a column of resistant rock standing.
Sea cave –wave action erodes base of cliff

35. Deposition: Sand bar and Spit
Sand bar: forms in the water
Spit: deposit that connects
two land masses

36. Changing Shape of the Shoreline
The shape of the shoreline results from changes in sea level.
Drop: cliffs and terraces
Rise: bays and harbors