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Unit 2 –
Weathering
and Erosion
Unit Essential Question (EQ) :
How do Earth’s processes and
human activities change the
surface of the Earth?
1
By the end of Unit 2, students will
understand that…
 Weathering is the process that breaks down rock and
other substances at Earth’s surface.
 Erosion is the movement of rock particles by water and
wind.
 Deposition occurs where the agents (forces) of erosion
lay down sediment.
 Weathering and erosion wear down, and deposition fills
in the Earth’s surface.
Students will also understand that…
 Although weathered rock is the basic
component of soil, the composition and
texture of soil and its fertility and
resistance to erosion are greatly influenced
by plants and other organisms.
 Human activities, such as reducing forest
cover and intensive farming have changed
the Earth’s surface.
Lesson Essential Questions (LEQs):
• How does weathering affect Earth’s
surface?
• How does erosion and deposition
affect Earth’s surface?
Weathering, Erosion, and
Deposition – Lesson vocabulary
Weathering
 What is weathering?
 What are the two types of weathering? How are they
different?
 What affects the rate (how fast or slow) at which
weathering occurs?
 What examples have you seen of each type of
weathering around the school, your home, or
community?
is the process that breaks down rock
and other substances at Earth’s surface.
These pieces do not move to a new
location. They simply break down but
remain next to one another.
Weathering
White lichens cover a blue
granite gravestone like
snow near Lake
Champlain, New York.
Lichens, symbiotic
organisms that combine
fungi and algae, can be
powerful weathering
agents, secreting
chemicals called chelates
that work to break down
rock.
is the movement of rock particles
by water and wind.
Lesson Essential Question (LEQ):
How does erosion and deposition
affect Earth’s surface?
Erosion by Gravity
 A landslides happen when lots of materials are carried
down a steep hill by gravity.
 A mudslide is when water makes the side of a hill heavy,
and carries it downward.
 Slumps occur when a large amount of rock or dirt, or
other sediments, fall. All the material in a slump always
comes down at once, where a landslide can have many
rocks tumbling down at different times.
 When the earth moves slowly, it's called a creep.
Erosion by Gravity
Slumps are landslides in which the moving material moves
in a block.
Erosion by Gravity
Creep is the gradual movement of soil down a
slope in response to gravity. This eventually
results in a mass downward movement of soil
on the slope.
Evidence of soil creep includes the
formation of step-like ridges along
the hillside, leaning walls and
telegraph poles, and trees that grow
in a curve to counteract progressive
leaning.
Erosion by Gravity
Landslides may involve
rock, debris (mixed rock and
soil) or earth (fine-grained
material).
← This slide cleared a long
path across route 121 and
down a forested hillside in
Wooden Valley, California.
Erosion by Gravity
A mudslide is when water
makes the side of a hill heavy,
and carries it downward.
Review Question:
The wearing away of soil and rock is called
__________.
A) runoff
B) Drainage
C) Erosion
D) infiltration
Water and Wind Erosion
 This is an
example of how
water and wind
can erode or
wear down the
Earth’s surface.
 Poor farming
practices allowed
soil erosion to
happen here very
quickly.
Picture taken in Providence Canyon State Park,
which is located 7 miles west of Lumpkin on Ga. Hwy.
39C.
Water Erosion
Moving water is among
the most powerful of
nature's landscapealtering tools.
Wind Erosion
Desert winds sculpted these gentle
swirls out of the limestone hills in Black
Gap Wildlife Management Area, Texas.
Winds sweeping through
the Grand Canyon have
eroded this sandstone
outcrop into an anvil
shape. Wind shapes these
fantastical forms by
eroding less dense rock,
like sandstone, faster than
surrounding rock.
Wind Erosion
Wind erosion makes these layered sandstone hills swirl in Paria
Canyon-Vermilion Cliffs Wilderness Area.
Glacial Erosion
The Bernard Glacier in
Alaska's Saint Elias
Mountains looks like a
huge alpine highway.
Glaciers are slow but
highly effective
shapers of the land,
essentially carrying
away anything in their
path—from soil and
rocks to hills and even
the sides of
mountains.
is when sediment, and broken down
substances are deposited, or dropped off
somewhere.
Deposition
 This can happen
in a river when the
water slows and
creates a new
bank, or delta.
← The Mekong Delta ( “Nine Dragon river
delta”) is the region in southwestern
Vietnam where the Mekong River
approaches and empties into the sea
through a network of distributaries.
Deposition
 When wind slows
down it can also
drop sediment.
Lesson Essential Question (LEQ):
• How does the formation of soil
relate to the processes of
weathering and erosion?
Formation/Composition of Soil –
Lesson vocabulary
Humus
How does the formation of soil relate to
the processes of weathering and erosion?
 What is soil?
 Soil is the loose weathered material on
Earth’s surface on which plants can grow.
 Makeup of soil includes rock particles,
minerals, decayed organic matter, water,
and air.
 Where did soil come from?
 One of the main ingredients of soil is
bedrock.
 Bedrock is a solid layer is rock beneath
the soil.
 How does bedrock become soil????
How does the formation of soil relate to
the processes of weathering and erosion?
 As we learned in the earlier part of this lesson and in
Unit 1, weathering and erosion both help to break
down rocks into smaller and smaller pieces.
 Weathering and erosion work together continuously
to wear down and carry away rocks at Earth’s surface.
 The bedrock will become exposed at the surface
where weathering will turn into sediment that helps
create soil.
How does the formation of soil relate to
the processes of weathering and erosion?
 Soil is constantly being formed where bedrock is
exposed.
 Soil continues to form as rock is broken down by
weathering.
 These rock particles mix with other materials on the
surface and the soil continues to develop.
 Soil takes a very long time to form.
How does the formation of soil relate to
the processes of weathering and erosion?
 You can see the different transitions or stages of soil
layers if you dig about half a meter deep.
 These different layers showing the gradual development
or changes in the soil are called a soil horizon.
 A soil horizon is a layer of soil that differs in color and
texture from the layers above or below it.
Go to www.phschool.com “Soil layers activity” - web code cfp-2022
Soil Profile
How does the formation of soil relate to
the processes of weathering and erosion?
 What factors affect the rate at which soil forms?
 The same things that affect the rate of weathering
also determine how fast or how slow soil forms!
 Climate
 Since weathering takes place faster in warm,
rainy climates, soil will develop faster in this
environment also.
 Rock type
 Some rocks weather faster than others. Rocks
that contain minerals that dissolve in water
or that are permeable, which means it has a
lot of tiny, connected air spaces in them,
weather faster.
limestone
Lesson Essential Questions (LEQs):
• How does human activity affect
the eroding of Earth’s surface?
• How can humans conserve water,
soil, and air?
Conservation – Lesson vocabulary
Wind breaks
Renewable Natural resources
How does human activity affect the
eroding of Earth’s surface?
 Human activities that have helped contribute to
soil erosion include:



Poor farming practices
Construction
Timber Industry
How does human activity
affect the eroding of
Earth’s surface?
 These are photographs from the Dust
Bowl of the 1930’s.
 Poor farming practices, which helped
increase soil erosion, was a major cause
that led to this devastating event.
Examples of Soil Conservation Techniques
– Contour Plowing and Terracing
← Alternating strips of alfalfa with corn on the
contour protects this crop field in northeast
Iowa from soil erosion.
How does human activity affect the
eroding of Earth’s surface?