Transcript Unit 8 Lesson 1 How Do Weathering and Erosion Shape Earth’s Surface? Copyright © Houghton Mifflin Harcourt Publishing Company.

Unit 8 Lesson 1 How Do Weathering and Erosion
Shape Earth’s Surface?
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 8 Lesson 1 How Do Weathering and Erosion Shape Earth’s Surface?
Objectives:
 Compare weathering and erosion.
 Explain the causes of weathering and erosion.
 Describe how erosion and deposition change Earth’s
surface.
Vocabulary:
•Weathering
•Erosion
•Deposition
•Sediment
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Unit 8 Lesson 1 How Do Weathering and Erosion Shape Earth’s Surface?
What Can Break a Boulder?
• The process of
rock breaking
apart is called
weathering.
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Unit 8 Lesson 1 How Do Weathering and Erosion Shape Earth’s Surface?
What Can Break a Boulder?
• Causes:
• gravity,
• flowing
water
• blowing
sand
• living things
• wind
• rain
• chemicals
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Unit 8 Lesson 1 How Do Weathering and Erosion Shape Earth’s Surface?
Rocks on the Move
• Weathering is the beginning of a series of changes that
often occurs to rocks on Earth’s surface.
• The process of moving weathered rock from one place to
another is called erosion.
• Moving water is one of the most common causes of
erosion.
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Unit 8 Lesson 1 How Do Weathering and Erosion Shape Earth’s Surface?
Rocks on the Move
• Fast-moving water and gravity can cause rocks to move
downhill.
• As the water in a river slows down, it has less energy
and cannot move the largest rocks and pebbles.
• The dropping of weathered rock by wind or moving water
is known as deposition.
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Unit 8 Lesson 1 How Do Weathering and Erosion Shape Earth’s Surface?
Rocks on the Move
• Slow-moving water has less energy than fast-moving
water has. Thus, as water in a river continues to slow
down, more bits of weathered rock are dropped.
• Slow-moving water carries only very small pieces of rock,
such as sand and silt, called sediment.
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Unit 8 Lesson 1 How Do Weathering and Erosion Shape Earth’s Surface?
Rocks on the Move
• What size of sediment drops out first? What size
drops out last?
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Unit 8 Lesson 1 How Do Weathering and Erosion Shape Earth’s Surface?
Rocks on the Move
• When rivers reach
the ocean, they
slow down even
more and
sediment is
dropped. Over
time, the sediment
forms a landform
called a delta.
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Unit 8 Lesson 1 How Do Weathering and Erosion Shape Earth’s Surface?
Exit slips
Active reading
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 8 Lesson 1 How Do Weathering and Erosion Shape Earth’s Surface?
Homework
brain check
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 8 Lesson 1 How Do Weathering and Erosion Shape Earth’s Surface?
Exit slip
braincheck
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 8 Lesson 1 How Do Weathering and Erosion Shape Earth’s Surface?
Blowing in the Wind
• A landform is a natural land
shape or feature.
Weathering and erosion by
wind change landforms.
• Wind can carry sediment
from place to place. When
wind deposits a lot of sand
in one area, sand dunes
form.
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Unit 8 Lesson 1 How Do Weathering and Erosion Shape Earth’s Surface?
Blowing in the Wind
• Wind sweeps up one side of a dune and lifts sand
from its surface. Gravity pulls the sand down the
other slope.
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Unit 8 Lesson 1 How Do Weathering and Erosion Shape Earth’s Surface?
Blowing in the Wind
• Blowing sediment can also
cause changes to other
landforms as particles
collide with exposed rock
to form interesting shapes.
• For instance, mushroom
rocks and arches are
formed by water but
shaped by the wind.
Eventually, gravity pulls
these formations down.
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Unit 8 Lesson 1 How Do Weathering and Erosion Shape Earth’s Surface?
Ice Carvings
• Huge sheets of ice are called
glaciers and are found in very cold
places.
• Gravity pulls glaciers downhill,
picking up soil, rocks, and boulders
beneath the glacier and pushing
boulders against the ground below.
• When the glacier melts, the rock
and sediment it carried downhill
drop out and form different land
features, including hills called
moraines.
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Unit 8 Lesson 1 How Do Weathering and Erosion Shape Earth’s Surface?
Ice Carvings
• A huge glacier once
covered most of
Canada and the
northern United
States. The ice cut
deep grooves that
formed the Great
Lakes.
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Unit 8 Lesson 1 How Do Weathering and Erosion Shape Earth’s Surface?
Exit slip
Active reading
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 8 Lesson 1 How Do Weathering and Erosion Shape Earth’s Surface?
Exit slip
Active reading
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 8 Lesson 1 How Do Weathering and Erosion Shape Earth’s Surface?
Can Waves Cut Caves?
• Moving water causes weathering
and erosion by picking up
sediment, which scrapes against
the bottom and sides of the
riverbed.
• This carves out deep canyons,
which are gorges between cliffs
of rock.
• Deposits of sediment can change
the direction of river water.
Curves in a river’s path can
produce different landforms.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 8 Lesson 1 How Do Weathering and Erosion Shape Earth’s Surface?
Can Waves Cut Caves?
• Ocean waves weather
cliffs, eroding pieces
of rock and
depositing them into
new places, forming
caves in shoreline
cliffs.
• The sediment from
eroding shorelines
becomes fine sand,
and beaches are
formed at the water’s
edge.
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Unit 8 Lesson 1 How Do Weathering and Erosion Shape Earth’s Surface?
Exit slips
Active reading
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 8 Lesson 1 How Do Weathering and Erosion Shape Earth’s Surface?
Homework
Braincheck
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Unit 8 Lesson 1 How Do Weathering and Erosion Shape Earth’s Surface?
Do Plants Protect Soil?
• In the early 1900s, families in
the central plains of the United
States made a living farming
land where natural grasses
once grew.
• In between crop seasons, loose
soil was left exposed to wind.
• During the 1930s, the plains
experienced severe drought.
The soil turned to fine, dry
dust, and high winds caused
giant dust storms.
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Unit 8 Lesson 1 How Do Weathering and Erosion Shape Earth’s Surface?
Do Plants Protect Soil?
• These dust storms stripped
away much of the soil that made
the region good for farming.
• Families moved away to find
other ways to survive. They
suffered hard times. The region
became known as the Dust
Bowl.
• The Dust Bowl teaches a
valuable lesson about erosion
problems caused by removing
all the plants from an area.
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Unit 8 Lesson 1 How Do Weathering and Erosion Shape Earth’s Surface?
Do Plants Protect Soil?
• Now farmers plant
different crops at
different times to keep
soil covered year-round.
• Fences and lines of trees
are planted to break the
wind, and plants are
added to hillsides to
protect soil from water
erosion and wind.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 8 Lesson 1 How Do Weathering and Erosion Shape Earth’s Surface?
Exit slips
Active reading
Copyright © Houghton Mifflin Harcourt Publishing Company