Weathering breaks rocks down into smaller pieces through physical or chemical processes when exposed to the atmosphere and hydrosphere. Physical weathering breaks rocks without changing their chemical composition through processes like frost wedging and abrasion. Chemical weathering alters the chemical composition of rocks through oxidation, hydrolysis, and carbonation. The products of weathering accumulate as soil and are further eroded by agents such as water, wind, and ice. Erosion transports eroded material which is eventually deposited elsewhere, usually in bodies of water, based on factors like particle size, shape, density, and transport velocity.

1. What Causes the
Landscape to be
Different?
Weathering
Erosion
Deposition

2. What is Weathering?
• Weathering is the chemical and
physical/mechanical processes that change the
characteristics of rocks on the Earth’s surface.
• Occurs when rocks are exposed to the hydrosphere
(water) and atmosphere (air)
• These weathering agents can change the physical
and chemical characteristics of rocks.

3. Physical/Mechanical Weathering
• Click for video on physical weathering
• when rocks are broken into smaller pieces
without changing the chemical composition of
the rock
• Different Types of Physical Weathering:
– Frost action/ice wedging
– Abrasion
– Exfoliation
– Wind

4. Click Picture for Lab

5. Frost action/ice wedging
• breakup of rock caused
by the freezing and
thawing (contracting
and expansion) of
water.
• Water seeps into cracks
of a rock and as the
climate cools the water
freezes and expands
breaking the rock apart.

6. Abrasion
• The physical wearing
down of rocks as they
rub or bounce against
each other.
• This process is most
common in windy
areas, under glaciers,
or in stream channels.

7. Exfoliation
• the peeling away of large sheets of loosened materials
at the surface of a rock.
• Common in shale, slate, and mica.
Enchanted State Rock Park, Texas

8. Wind

9. Chemical Weathering
• Click for video on chemical weathering
• occurs when a rock is broken down by
chemical action resulting in a change in the
composition of a rock.
• Main agents of chemical weathering are:
• -oxygen -rainwater
• -carbon dioxide -acids produced by
decaying plants and
animals that leads to the
formation of soil.

10. Types of Chemical Weathering
• Oxidation
– when oxygen interacts chemically with minerals.
(ex. when a nail rusts)
• Hydration/Hydrolysis
– when water interacts chemically with minerals. (ex:
when hornblende and feldspar join with water they
eventually form into clay)
• Carbonation
– when carbon dioxide interacts chemically with
minerals. Forms carbonic acid--> ex:dissolves
limestone creating caverns and caves. Karst
Topography

11. Oxidation

12. Carbonation

13. Carbonation: Acid Rain

14. Karst Topography

15. Karst Topography
• Occurs in limestone bedrock
• limestone easily weathers
chemically (carbonation) by weak
acids in groundwater
• landforms created:
–caverns
–sinkholes
–disappearing rivers

16. Stalactites and Stalagmites

17. Sinkholes

19. Weathering Rates
Depend on 3 Factors
• Particle size/surface area exposed to the
surface
• Mineral composition
• Climate

20. What is a Major Product of
Weathering?
• Soil:
– is a combination of particles of rocks,
minerals, and organic matter produced
through weathering processes.
– contains the necessary nutrients to support
various forms of plant and animal life.
• As a result of weathering processes and biologic
activity, soil horizons (layers) form.

21. Soil Horizons
• vary in depth depending on an areas climate and
weathering rates
• Soil Horizons:
– O Horizon
– A Horizon
– B Horizon
– C Horizon
– D Horizon

22. • Horizon O refers to the organic material on the
upper most part of the profile (this layer is
usually very thin).
• Horizon A commonly known as topsoil. this
layer includes organic material (humus), such as
fallen leaves, twigs, decaying plant and animal
remains.
• The material helps prevent erosion, holds
moisture, and decays to form a very rich soil
known as humus.
• Provides plants with nutrients

23. • Horizon B is known as the subsoil.
• much less humus.
• usually will contain a fair amount of clay and
iron oxides, but also may contain some elements
from horizon A because of the process of
leaching.
• Leaching resembles what happens in a coffee pot
as the water drips through the coffee grounds.
Leaching may also bring some minerals from
horizon B down to horizon C.

24. • Horizon C consists mostly of weatherized
big rocks known as Parent material (the
rock that the soil formed from).
• Horizon D which is not shown in this
illustration, usually contains solid bedrock.

25. Erosion
• Erosion refers to the transportation of rock, soil,
and mineral particles from one location to
another.
• Erosion is different from weathering since
erosion has the moving element.
• The main driving force behind all agents of
erosion is gravity.
• Without gravity the other major natural agents of
erosion such as: wind, running water, glaciers,
waves, and rain would not occur.

26. Factors Affecting Transportation
of Sediment
• Running water is the primary agent of
erosion on Earth.
• Most running water is found in streams and
rivers.
• Sediments carried by a stream are almost always
rounded due to the grinding action of the water
on the rocks, a process called abrasion
• There are many factors that affect the movement
of sediments in a stream.

27. Factors Affecting Transportation
of Sediment
• Gradient (slope), discharge, and channel shape
influence a stream’s velocity and the erosion
and deposition of sediments
• V-shaped valleys are eroded by streams and
U-shaped valleys are eroded by glaciers
• deltas, flood plains, and meanders are results
of what a stream can form.
• The watershed of a stream is the area drained
by a stream and its tributaries (smaller feeder
streams).

29. http://regentsprep.org/Regents/earthsci/units/weathering/erosion.cfm

30. Delta and Floodplains
Delta
Floodplains

31. Floodplain Development
Floodplain of creek near Millersville, NC
Photograph by Jimmie D. Agnew
Normal Stage

32. Floodplain Development
Rain Stage
Creek with floodplain near Millersville, NC
Photograph by Jimmie D. Agnew

33. Floodplain Development
Creek at flood stage, occupting part of its floodplain near
Millersville, NC
Photograph by Jimmie D. Agnew
Flood Stage

34. M E
A
N
D
E
R I N G
S
T
R E
A M

35. Meandering Stream with development
of Oxbow Lakes and an Oxbow lake

36. Water Erosion by Wave Action

37. Water Erosion

38. Erosion by Gravity: Landslide

39. Wind Erosion

40. Deposition
• is the final step in the erosional-depositional
system.
• Rock particles picked up and transported will
ultimately be deposited (left behind) somewhere
else.
• Final deposition of particles (sediments) usually
occurs at the mouth of a stream. This is due to
the faster flowing stream emptying into a slower
larger body of water.
• The sediments that were once carried down the
stream are arranged from largest to smallest.

41. Factors Affecting Deposition
• particle size,
• shape,
• density, and
• the velocity of the transporting stream.

42. Particle Size
• smaller particles settle
more slowly than the
larger particles, due to
the pull of gravity.
• The smaller particles
tend to stay in
suspension for longer
periods of time.
• This form of deposition
is called graded
bedding
• Click on picture

43. Particle Shape
• A round sediment
compared to a flat
(skipping stone) sediment
of equal size will settle
faster in a body of water.
• This is due to the resistance
the flat particle will
undergo as it settles
through the water. The
round particle will meet
little resistance and settle at
a must faster rate.

44. Density and Velocity
• Density:
– If particles are the
same size but have
different densities
the higher density
particle will settle
faster.
• Velocity:
– velocity (speed) of the
transporting stream determines
when sediments will be deposited.
– If the stream slows down, carrying
power will decrease and the
particle sizes carried and
deposited will also decrease.
– If a stream is flowing faster, then
the carrying power of the stream
will increase and the sizes of
particles deposited will increase as
well.

45. Deposition & Erosion of a Stream

46. Glacial Deposition
• As glaciers move over the land they act as a
"bulldozer" changing the view of the
landscape
• As glaciers pass over the land they leave
distinct features

47. Glacial Deposition

48. Let’s Review
• Click for Review of Weathering and Erosion

49. References
• http://regentsprep.org/Regents/earthsci/units/weathering/in
dex.cfm
• www.elon.edu/ geo/new_river.htm
• http://libraries.risd.org/skylib/SCIENCE
PAGE/Erosion_and_weathering.htm