Weathering, Erosion, and Deposition

1
Weathering, Erosion, and Deposition
2
1. Weathering

• Weathering is the breakdown of rock at the
  Earths surface.
• Some of these changes happen quickly and some
  happen slowly.
• The most important factors in determining the
  rate of weathering are the type of rock and the
  climate.
• There are 2 Types
• Mechanical and Chemical

3
2. Mechanical or Physical Weathering

• Mechanical Weathering the type of weathering in
  which rock is physically broken into smaller
  pieces.
• This can be caused by freezing and thawing,
  release of pressure, growth of plants, and
  actions of
• animals (including
• humans).

4
3. Freezing and Thawing

• Example
• Water seeps into a crack in a rock
• When the water freezes, it expands

• The force of the water expanding applies pressure
  on the rock and causes it to crack more.
• This is called ice wedging

5
Ice Wedging
6
4. Plant Growth

• Roots of trees and other plants enter into cracks
  of rocks.
• As the plants get bigger, so do the roots.
• The growing roots force the cracks further apart.

7
Plant Roots
8
5. Abrasion

• Abrasion is the grinding away of rock by other
  rock particles.
• These rock particles can be carried by water,
  ice, wind, or gravity.
• These particles scrape away at other rocks like
  sandpaper on wood as they rub or roll against the
  surface.

9
Water Abrasion
10
6. Plucking

• As glaciers move across the Earths surface, they
  pick up rocks and sediment.
• As the glaciers continue to move, the rocks and
  sediment scrape and gouge the Earth below.

11
7. Chemical Weathering

• Chemical weathering is the processes of breaking
  down rock through chemical changes.
• The agents of (or things that cause) chemical
  weathering include water, oxygen, carbon
  dioxide, living organisms (like lichens) and acid
  rain.
• Chemical weathering occurs more rapidly in warm
  wet climates.

12
8. Chemical Change

• Chemical Weathering changes the mineral makeup of
  rocks. (There is a chemical change that takes
  place.)
• Water dissolves rocks over time
• Oxygen causes oxidation (rusting)
• Acid rain reacts with marble and limestone
• Living organisms plant roots produce weak acids
  to dissolve rock around the roots, Lichens also
  produce acids that dissolve rocks.

13
Water

• Water weathers rock by dissolving it

14
Oxygen

• Iron combines with oxygen in the presence of
  water in a processes called oxidation
• The product of oxidation is rust

15
Acid Rain

• Compounds from burning coal, oil and gas react
  chemically with water forming acids.
• Acid rain causes very rapid chemical weathering

16
Living Organisms

• Lichens that grow on rocks produce weak acids
  that chemically weather rock

17
CPS Quiz

• What type of weathering do each example cause?
• The roots of a plant
• An animal scratching
• Oxygen
• Water freezing
• Acid rain
• Wind
• Water
• A glacier

• Chemical Weathering
• Mechanical Weathering
• Both types of weathering

18
9. Erosion

• When rock and soil are moved from one place to
  another by natural forces, this is called
  Erosion.
• The agents of Erosion are
• Water (rain water runoff, streams, rivers,
  groundwater, and waves)
• Ice (Glaciers)
• Wind
• Gravity ( landslides,
• mudslides, avalanches etc.)

19
Water Erosion

• Rivers, streams, and runoff

20
Ice Erosion

• Glaciers

21
Wind Erosion
22
Mass Movements

• Landslides, mudslides, creep

landslide clip.mpeg
23
10. Sediment

• The material moved by erosion is sediment.
• Sediment is small, solid particles of rocks or
  organisms.

24
11. Deposition

• When the sediment being carried is dropped (or
  deposited) in a new area, it is called
  deposition.
• Depositions can create new landforms like beaches
  and sand dunes.

25
CPS Quiz

• Choose one of the following for each example
• Erosion
• Deposition

• A river carrying sand
• Dropping sediment in a new location
• A glacier picking up a rock in its path.
• A beach is formed.
• How a sand dune is created
• How sediment is moved
• Sand being carried by the wind in a sandstorm.

26
CPS Quiz Where would the evidence of
weathering, erosion or deposition be most likely
to be found?

• Wet, warm climates
• A dessert area with little vegetation and high
  winds
• An area that was once covered by a continental
  glacier
• An area where it freezes and thaws often

• Deep gouges in the ground
• Evidence of wind abrasion
• Big rocks with deep cracks splitting them apart
• Crumbly rocks with a red or brown color

27
In each of the following slides, decide which
type of weathering you think occurred.
28
Weathering
29
Abrasion, Water
30
Ice wedging, Oxidation
31
Oxidation, Plant Action
32
Plant Action, Oxidation
33
Release of Pressure
34
Oxidation, Ice Wedging
35
Acid rain
36
Abrasion, Water
37
Acid Rain
38
Release of Pressure
39
Living organism lichen, Plant Action
40
Oxidation, Release of Pressure
41
Abrasion, Oxidation
42
Summary Questions

• Predict what would happen to a large boulder with
  several cracks in it. What would you expect to
  see if you could observe the boulder again in
  several hundred years? Explain.
• Suppose mechanical weathering breaks a rock into
  pieces. How would this affect the rate at which
  the rock weathers chemically?
• On the moon there is no air or water. Develop a
  hypothesis about the rate rocks would weather on
  the moon compared with their rate of weathering
  on Earth. Explain.

43
Yet More Summary Questions

• A river that has the most erosional impact most
  likely moves at a speed of which of the
  following 200 meters per second or 15 meters per
  second. Explain.
• Describe how human activity can affect the impact
  of weathering, erosion and deposition on the
  Earths surface.

44
Yet EVEN More Summary Questions!!!

• Just Kidding!!!