Transcript Chapter 14

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Chapter 14
Weathering and Erosion
Table of Contents
Section 1 Weathering Processes
Section 2 Rates of Weathering
Section 3 Soil
Section 4 Erosion
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Chapter 14
Section 1 Weathering Processes
Objectives
• Identify three agents of mechanical weathering.
• Compare mechanical and chemical weathering
processes.
• Describe four chemical reactions that decompose
rock.
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Chapter 14
Section 1 Weathering Processes
Weathering Processes
weathering the natural process by which atmospheric
and environmental agents, such as wind, rain, and
temperature changes, disintegrate and decompose
• There are two main types of weathering processes—
mechanical weathering and chemical weathering.
• Each type of weathering has different effects on rock.
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Chapter 14
Section 1 Weathering Processes
Mechanical Weathering
mechanical weathering the process by which rocks
break down into smaller pieces by physical means
• Mechanical weathering is strictly a physical process
and does not change the composition of the rock.
• Common agents of mechanical weathering are ice,
plants and animals, gravity, running water, and wind.
• Physical changes within the rock itself affect
mechanical weathering.
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Chapter 14
Section 1 Weathering Processes
Mechanical Weathering, continued
Ice Wedging
• A type of mechanical weathering that occurs in cold
climates is called ice wedging.
• Ice wedging occurs when water seeps into the cracks
in rock and freezes.
• When the water freezes, its volume increases by
about 10% and creates pressure on the surrounding
rock.
• This process eventually splits the rock apart.
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Chapter 14
Section 1 Weathering Processes
Mechanical Weathering, continued
Abrasion
abrasion the grinding and wearing away of rock
surfaces through the mechanical action of other rock
or sand particles
• Abrasion is caused by gravity, running water, and
wind.
• Wind is another agent of abrasion.
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Chapter 14
Section 1 Weathering Processes
Reading Check
Describe two types of mechanical weathering.
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Chapter 14
Section 1 Weathering Processes
Reading Check
Describe two types of mechanical weathering.
Two types of mechanical weathering are ice wedging
and abrasion. Ice wedging is caused by water that
seeps into cracks in rock and freezes. When water
freezes, it expands and creates pressure on the rock,
which widens and deepens cracks. Abrasion is the
grinding away of rock surfaces by other rocks or sand
particles. Abrasive agents may be carried by gravity,
water, and wind.
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Chapter 14
Section 1 Weathering Processes
Mechanical Weathering, continued
Organic Activity
• Plants and animals are important agents of
mechanical weathering.
• As plants grow, the roots grow and expand to create
pressure that wedge rock apart.
• Earthworms and other animals that move soil expose
new rock surfaces to both mechanical and chemical
weathering.
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Chapter 14
Section 1 Weathering Processes
Chemical Weathering
chemical weathering the process by which rocks
break down as a result of chemical reactions
• Chemical reactions commonly occur between rock,
water, carbon dioxide, oxygen, and acids.
• Bases can also chemically weather rock.
• Chemical weathering changes both the composition
and physical appearance of the rock.
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Chapter 14
Section 1 Weathering Processes
Chemical Weathering, continued
Oxidation
oxidation a reaction that moves one or more electrons
from a substance such that the substance’s valence
or oxidation state increases; in geology, the process
by which an element combines with oxygen
• Oxidation commonly occurs in rock that has ironbearing minerals, such as hematite and magnetite.
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Chapter 14
Section 1 Weathering Processes
Chemical Weathering, continued
Oxidation, continued
• Iron, Fe, in rocks and soil combines quickly with
oxygen, O2, that is dissolved in water to form rust, or
iron oxide, Fe2O3.
4Fe + 3O2  2Fe2O3
• The red color of much of the soil in the southeastern
United States is due to mainly the presence of iron
oxide produced by oxidation.
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Chapter 14
Section 1 Weathering Processes
Reading Check
Describe two effects of chemical weathering.
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Chapter 14
Section 1 Weathering Processes
Reading Check
Describe two effects of chemical weathering.
Two effects of chemical weathering are changes in the
chemical composition and changes in the physical
appearance of a rock.
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Chapter 14
Section 1 Weathering Processes
Chemical Weathering, continued
Hydrolysis
hydrolysis a chemical reaction between water and
another substance to form two or more new
substances
• Water plays a crucial role in chemical weathering.
• Minerals that are affected by hydrolysis often dissolve
in water.
• Water can then carry the dissolved minerals to lower
layers of rock in a process called leaching.
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Chapter 14
Section 1 Weathering Processes
Chemical Weathering, continued
The image below shows how water plays a crucial role in chemical
weathering.
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Chapter 14
Section 1 Weathering Processes
Chemical Weathering, continued
Carbonation
carbonation the conversion of a compound into a
carbonate
• When carbon dioxide, CO2, from the air dissolves in
water, H2O, a weak acid called carbonic acid, H2CO3,
forms.
H2O + CO2  H2CO3
• Carbonic acid has a higher concentration of
hydronium ions than pure water does, which speeds
up the process of hydrolysis.
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Chapter 14
Section 1 Weathering Processes
Chemical Weathering, continued
Organic Acids
• Acids are produced naturally by certain living
organisms.
• Lichens and mosses grow on rocks and produce
weak acids that can weather the surface of the rock.
• The acids seep into the rock and produce cracks that
eventually cause the rock to break apart.
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Chapter 14
Section 1 Weathering Processes
Chemical Weathering, continued
Acid Precipitation
acid precipitation precipitation, such as rain, sleet, or
snow, that contains a high concentration of acids,
often because of the pollution of the atmosphere
• Acid precipitation weathers rock faster than ordinary
precipitation does.
• Rainwater is slightly acidic because it combines with
small amounts of carbon dioxide.
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Chapter 14
Section 1 Weathering Processes
Chemical Weathering, continued
Acid Precipitation, continued
• But when fossil fuels, especially coal, are burned,
nitrogen oxides and sulfur dioxides are released into
the air. These compounds combine with water in the
atmosphere to produce nitric acid, nitrous acid, or
sulfuric acid.
• The occurrence of acid precipitation has been greatly
reduced since power plants have installed scrubbers
that remove much of the sulfur dioxide before it can
be released.
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Chapter 14
Section 1 Weathering Processes
Ice Wedging
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Chapter 14
Section 2 Rates of Weathering
Objectives
• Explain how rock composition affects the rate of
weathering.
• Discuss how surface area affects the rate at which
rock weathers.
• Describe the effects of climate and topography on
the rate of weathering.
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Chapter 14
Section 2 Rates of Weathering
Rates of Weathering
• The processes of mechanical and chemical
weathering generally work very slowly.
• The rate at which rock weathers depends on a
number of factors, including rock composition,
climate, and topography.
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Chapter 14
Section 2 Rates of Weathering
Differential Weathering
differential weathering the process by which softer,
less weather resistant rocks wear away at a faster
rate than harder, more weather resistant rocks do
• When igneous rocks that are rich in the mineral
quartz are exposed on Earth’s surface, they remain
basically unchanged, even after all of the surrounding
sedimentary rock has weathered away.
• They remain unchanged because the chemical
composition and crystal structure of quartz make
quartz resistant to chemical weathering.
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Chapter 14
Section 2 Rates of Weathering
Rock Composition
• Limestone and other sedimentary rocks that contain
calcite are weathered most rapidly. They weather
rapidly because they commonly undergo carbonation.
• Other sedimentary rocks are affected mainly by
mechanical weathering processes.
• The rates at which these rocks weather depend
mostly on the material that holds the sediment grains
together.
• For example, shales and sandstones that are not
firmly cemented together gradually break up to
become clay and sand particles.
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Chapter 14
Section 2 Rates of Weathering
Amount of Exposure
Surface Area
• Both chemical and mechanical weathering may split
rock into a number of smaller rocks.
• The part of a rock that is exposed to air, water, and
other agents of weathering is called the rock’s
surface area.
• As a rock breaks into smaller pieces, the surface
area that is exposed increases.
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Chapter 14
Section 2 Rates of Weathering
Amount of Exposure, continued
The image below shows the ratio of total surface area to volume.
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Chapter 14
Section 2 Rates of Weathering
Amount of Exposure, continued
Fractures and Joints
• Most rocks on Earth’s surface contain natural
fractures and joints.
• These structures are natural zones of weakness
within the rock.
• Fractures and joints increase the surface area of a
rock and allow weathering to take place more rapidly.
• They also form natural channels through which
water flows.
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Chapter 14
Section 2 Rates of Weathering
Reading Check
How do fractures and joints affect surface area?
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Chapter 14
Section 2 Rates of Weathering
Reading Check
How do fractures and joints affect surface area?
Fractures and joints in a rock increase surface area and
allow weathering to occur more rapidly.
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Chapter 14
Section 2 Rates of Weathering
Climate
• In general, climates that have alternating periods of
hot and cold weather allow the fastest rates of
weathering.
• In warm, humid climates, chemical weathering is also
fairly rapid. The constant moisture is highly
destructive to exposed surfaces.
• The slowest rates of weathering occur in hot, dry
climates. The lack of water limits many weathering
processes, such as carbonation and ice wedging.
• Weathering is also slow in very cold climates.
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Chapter 14
Section 2 Rates of Weathering
Topography
• Because temperatures are generally cold at high
elevations, ice wedging is more common at high
elevations than at low elevations.
• On steep slopes, such as mountainsides, weathered
rock fragments are pulled downhill by gravity and
washed out by heavy rains.
• As a result of the removal of these surface rocks,
new surfaces of the mountain are continually
exposed to weathering.
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Chapter 14
Section 2 Rates of Weathering
Human Activities
• Mining and construction often expose rock surfaces
to agents of weathering.
• Mining also often exposes rock to strong acids and
other chemical compounds that are used in mining
processes.
• Recreational activities such as hiking or riding allterrain vehicles can also speed up weathering by
exposing new rock surfaces.
• Rock that is disturbed or broken by human activities
weathers more rapidly than undisturbed rock does.
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Chapter 14
Section 2 Rates of Weathering
Plant and Animal Activities
• Rock that is disturbed or broken by plants or animals
also weathers more rapidly than undisturbed rock
does.
• The roots of plants and trees often break apart rock.
• Burrowing animals dig holes into rock and soil.
• Some biological wastes of animals can cause
chemical weathering.
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Chapter 14
Section 2 Rates of Weathering
Dissolving Process
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Chapter 14
Section 3 Soil
Objectives
• Summarize how soil forms.
• Explain how the composition of parent rock affects
soil composition.
• Describe the characteristic layers of mature residual
soils.
• Predict the type of soil that will form in arctic and
tropical climates.
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Chapter 14
Section 3 Soil
Soil
soil a loose mixture of rock fragments and organic
material that can support the growth of vegetation
• One result of weathering is the formation of regolith,
a layer of weathered rock fragments that covers
much of Earth’s surface.
• Bedrock is the solid, unweathered rock that lies
beneath the regolith.
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Chapter 14
Section 3 Soil
Characteristics of Soil
• The characteristics of soil depend mainly on the rock
from which the soil was weathered, which is called
the soil’s parent rock.
Soil Composition
• Soil composition refers to the materials of which it is
made.
• The color of soil is related to the composition of the
soil.
• Soil moisture can also affect color.
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Chapter 14
Section 3 Soil
Characteristics of Soil, continued
Soil Texture
• Rock material in soil consists of three main types:
clay, silt, and sand.
• Clay particles have a diameter of less than 0.004
mm. Silt particles have a diameter from 0.004 to 0.06
mm. Sand particles have diameters from 0.06 to
2mm.
• The proportion of clay, silt, and sand in soil depends
on the soil’s parent rock.
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Chapter 14
Section 3 Soil
Soil Profile
soil profile a vertical section of soil that shows the
layers of horizons
horizon a horizontal layer of soil that can be
distinguished from the layers above and below it; also
a boundary between two rock layers that have
different physical properties
• Transported soils are commonly deposited in
unsorted masses. However, residual soils commonly
develop distinct layers over time.
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Chapter 14
Section 3 Soil
Soil Profile, continued
humus dark, organic material formed in soil from the
decayed remains of plants and animals
• Residual soils generally consist of three main horizons.
• The A horizon, or topsoil, is a mixture of organic
materials and small rock particles.
• The B horizon or subsoil, contains the minerals
leached from the topsoil, clay, and sometimes, humus.
• The C horizon consists of partially-weathered
bedrock.
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Section 3 Soil
Soil Profile, continued
The image below shows the soil horizons of residual soils.
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Chapter 14
Section 3 Soil
Soil and Climate
• Climate is one of the most important factors that
influences soil formation.
• Climate determines the weathering processes that
occur in a region.
• These weathering processes, in turn, help determine
the composition of soil.
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Chapter 14
Section 3 Soil
Soil and Climate, continued
Tropical Soils
• In humid tropical climates, where much rain falls and
where temperatures are high, chemical weathering
causes thick soils to develop rapidly.
• Leached minerals from the A horizon sometimes
collect in the B horizon.
• Heavy rains, which are common in tropical climates,
cause a lot of leaching of the topsoil, and thus keep the
A horizon thin.
• A thin layer of humus usually covers the B horizon.
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Section 3 Soil
Soil and Climate, continued
Temperate Soils
• In temperate climates, where temperatures range
between cool and warm and here rainfall is not
excessive, both mechanical and chemical weathering
occur.
• All three soil horizons in temperate soils may reach a
thickness of several meters.
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Chapter 14
Section 3 Soil
Reading Check
Compare the formation of tropical soils and temperate
soils.
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Chapter 14
Section 3 Soil
Reading Check
Compare the formation of tropical soils and temperate
soils.
Large amounts of rainfall and high temperatures cause
thick soils to form in both tropical and temperate
climates. Tropical soils have thin A horizons because
of the continuous leaching of topsoil. Temperate soils
have three thick layers, because leaching of the A
horizon in temperate climates is much less than
leaching of the A horizon in tropical climates.
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Chapter 14
Section 3 Soil
Soil and Climate, continued
Desert and Arctic Soils
• In desert and arctic climates, rainfall is minimal and
chemical weathering occurs slowly.
• As a result, the soil is thin and consists mostly of
regolith—evidence that soil in these areas form
mainly by mechanical weathering.
• Desert and arctic climates are also often too warm or
too cold to sustain life, so their soils have little
humus.
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Chapter 14
Section 3 Soil
Soil and Climate, continued
Soil and Topography
• Because rainwater runs down slopes, much of the
topsoil of the slope washes away.
• Therefore, the soil at the top and bottom of a slope
tends to be thicker than the soil on the slope.
• Topsoil that remains on a slope is often too thin to
support dense plant growth.
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Chapter 14
Section 3 Soil
Soils and the Effects of Climate
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Chapter 14
Section 4 Erosion
Objectives
• Define erosion, and list four agents of erosion.
• Identify four farming methods that conserve soil.
• Discuss two ways gravity contributes to erosion.
• Describe the three major landforms shaped by
weathering and erosion.
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Chapter 14
Section 4 Erosion
Erosion
erosion a process in which the materials of Earth’s
surface are loosened, dissolved, or worn away and
transported from one place to another by a natural
agent, such as wind, water, ice, or gravity
• When rock weathers, the resulting rock particles do
not always stay near the parent rock.
• Various forces may move weathered fragments of
rock away from where the weathering occurred.
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Chapter 14
Section 4 Erosion
Soil Erosion
• Ordinarily, new soil forms about as fast as existing
soil erodes.
• Some farming and ranching practices increase soil
erosion.
• Soil erosion is considered by some scientists to be
the greatest environmental problem that faces the
world today.
• This erosion prevents some countries from growing
the crops needed to prevent widespread famine.
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Chapter 14
Section 4 Erosion
Soil Erosion, continued
Gullying and Sheet Erosion
• One farming technique that can accelerate soil
erosion is the plowing of furrows, or long, narrow
rows.
• As soil is washed away with each rainfall, a furrow
becomes larger and forms a small gully.
• Eventually land that is plowed in this way can
become covered with deep gullies.
• This type of accelerated soil erosion is called
gullying.
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Section 4 Erosion
Soil Erosion, continued
Gullying and Sheet Erosion, continued
sheet erosion the process by which water flows over a
layer of soil and removes the topsoil
• Another type of soil erosion strips away parallel
layers of top soil.
• Sheet erosion may occur where continuous rainfall
washes away layers of the topsoil.
• Wind also can cause sheet erosion during unusually
dry periods.
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Section 4 Erosion
Soil Erosion, continued
The image below shows a map of soil vulnerability worldwide to erosion by
water.
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Chapter 14
Section 4 Erosion
Reading Check
Describe one way a dust storm may form, and explain
how a dust storm can affect the fertility of land.
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Chapter 14
Section 4 Erosion
Reading Check
Describe one way a dust storm may form, and explain
how a dust storm can affect the fertility of land.
Dust storms may form during droughts when the soil is
made dry and loose by lack of moisture and windcaused sheet erosion carries it away in clouds of
dust. If all of the topsoil is removed, the remaining
subsoil will not contain enough nutrients to raise
crops.
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Chapter 14
Section 4 Erosion
Soil Erosion, continued
Results of Soil Erosion
• Constant erosion reduces the fertility of the soil be
removing the A horizon, which contains the fertile
humus.
• The B horizon, which does not contain much organic
matter, is difficult to farm because it is much less
fertile than the A horizon.
• Without plants, the B horizon has nothing to protect it
from further erosion.
• So, within a few years, all the soil layers could be
removed by continuous erosion.
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Chapter 14
Section 4 Erosion
Soil Conservation
• Certain farming and grazing techniques and
construction projects can also increase the rate of
erosion.
• This land clearing removes protective ground cover
plants and accelerates topsoil erosions.
• But rapid, destructive soil erosion can be prevented
by soil conservation methods.
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Chapter 14
Section 4 Erosion
Soil Conservation, continued
Contour Plowing
• Farmers in countries around the world use planting
techniques to reduce soil erosion.
• In one method, called contour plowing, soil is plowed
in curved bands that follow the contour, or shape of
the land.
• This method of planting prevents water from flowing
directly down slopes, so the method prevents
gullying.
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Chapter 14
Section 4 Erosion
Soil Conservation, continued
Strip-Cropping
• In strip-cropping, crops are planted in alternating
bands.
• The cover crop protects the soil by slowing the runoff
of rainwater.
• Strip-cropping is often combined with contour
plowing. The combination of these two methods can
reduce soil erosion by 75%.
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Chapter 14
Section 4 Erosion
Soil Conservation, continued
Terracing
• The construction of steplike ridges that follow the
contours of a sloped field is called terracing.
• Terraces, especially those used for growing rice in
Asia, prevent or slow the downslope movement of
water and thus prevent rapid erosion.
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Chapter 14
Section 4 Erosion
Soil Conservation, continued
Crop Rotation
• In crop rotation, farmers plant one type of crop one
year and a different type of crop the next.
• For example, crops that expose the soil to the full
effects of erosion may be planted one year, and a
cover crop will be planted the next year.
• Crop rotation stops erosion in its early stages, which
allows small gullies that formed during one growing
season to fill with soil during the next one.
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Chapter 14
Section 4 Erosion
Gravity and Erosion
mass movement the movement of a large mass of
sediment or a section of land down a slope
• Gravity causes rock fragments to move down
inclines.
• Some mass movements occur rapidly, and others
occur very slowly.
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Section 4 Erosion
Gravity and Erosion, continued
Rockfalls and Landslides
• The most dramatic and destructive mass
movements occur rapidly.
• The fall of rock from a steep cliff is called a rockfall.
A rockfall is the fastest kind of mass movement.
• When masses of loose rock combined with soil
suddenly fall down a slope, the event is called a
landslide.
• Heavy rainfall, spring thaws, volcanic eruptions,
and earthquakes can trigger landslides.
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Chapter 14
Section 4 Erosion
Reading Check
What is the difference between a rockfall and a
landslide?
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Chapter 14
Section 4 Erosion
Reading Check
What is the difference between a rockfall and a
landslide?
Landslides are masses of loose rock combined with soil
that suddenly fall down a slope. A rockfall consists of
rock falling from a steep cliff.
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Chapter 14
Section 4 Erosion
Gravity and Erosion, continued
Mudflows and Slumps
• The rapid movement of a large amount of mud
creates a mudflow.
• Mudflows occur in dry, mountainous regions during
sudden, heavy rainfall or as a result of volcanic
eruptions.
• Mud churns and tumbles as it moves down slopes
and through valleys, and it frequently spreads out in
a large fan shape at the base of the slope.
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Chapter 14
Section 4 Erosion
Gravity and Erosion, continued
Mudflows and Slumps, continued
• Sometimes, a large block of soil and rock becomes
unstable and moves downhill in one piece.
• The block of soil then slides along the curved slope of
the surface. This type of movement is called a slump.
• Slumping occurs along very steep slopes. Saturation
by water and loss of friction within underlying rock
causes loose soil to slip downhill over the solid rock.
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Chapter 14
Section 4 Erosion
Gravity and Erosion, continued
Solifluction
solifluction the slow, downslope flow of soil saturated
with water in areas surrounding glaciers at high
elevations
• Solifluction occurs in arctic and mountainous climates
where the subsoil is permanently frozen. In the spring
and summer, only the top layer of soil thaws.
• Solifluction can also occur in warmer regions, where
the subsoil consists of hard clay.
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Chapter 14
Section 4 Erosion
Gravity and Erosion, continued
Creep
creep the slow downhill movement of weathered rock
material
• Soil creep moves the most soil of all types of mass
movements. But creep may go unnoticed unless
buildings, fences, or other surface objects move
along with the soil.
• Many factors contribute to soil creep.
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Chapter 14
Section 4 Erosion
Erosion and Landforms
landforms a physical feature of Earth’s surface
• There are three major landforms that are shaped by
weathering and erosion—mountains, plains, and
plateaus. Minor landforms include hills, valleys, and
dunes.
• All landforms are subject to two opposing processes.
One process bends, breaks and lifts Earth’s crust and
thus creates elevated, or uplifted, landforms. The
other process is weathering and erosion, which
wears down land surfaces.
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Chapter 14
Section 4 Erosion
Erosion and Landforms, continued
Erosion of Mountains
• During the early stages in the history of a mountain,
the mountain undergoes uplift.
• When the forces stop uplifting the mountain,
weathering and erosion wear down the rugged peaks
to rounded peaks and gentle slopes.
• Over millions of years, mountains that are not being
uplifted become low, featureless surfaces. These
areas are called peneplains, which means “almost
flat.”
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Chapter 14
Section 4 Erosion
Reading Check
Describe how a mountain changes after it is no longer
uplifted.
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Chapter 14
Section 4 Erosion
Reading Check
Describe how a mountain changes after it is no longer
uplifted.
When a mountain is no longer being uplifted,
weathering and erosion wear down its jagged peaks
to low, featureless surfaces called peneplains.
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Chapter 14
Section 4 Erosion
Erosion and Landforms, continued
Erosion of Plains and Plateaus
• A plain is a relatively flat landform near sea level. A
plateau is a broad, flat landform that has a high
elevation.
• A plateau is subject to much more erosion than a
plain.
• The effect of weathering and erosion on a plateau
depends on the climate and the composition and
structure of the rock.
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Chapter 14
Section 4 Erosion
Erosion and Landforms, continued
Erosion of Plains and Plateaus, continued
•
As a plateau ages, erosion may dissect the plateau
into smaller, tablelike areas called mesas.
•
Mesas ultimately erode to small, narrow-topped
formations called buttes.
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Chapter 14
Section 4 Erosion
Mass Movement and Angle of Repose
QuickTime™ and a
Sorenson Video 3 decompressor
are needed to see this picture.
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Chapter 14
Weathering and Erosion
Brain Food Video Quiz
QuickTime™ and a
3ivx D4 4.5.1 decompressor
are needed to see this picture.
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Chapter 14
Maps in Action
Maps in Action
Soil Map of North Carolina
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Chapter 14
Standardized Test Prep
Multiple Choice
1. The processes of physical weathering and erosion
shape Earth’s landforms by
A.
B.
C.
D.
expanding the elevation of Earth’s surface
decreasing the elevation of Earth's surface
changing the composition of Earth’s surface
bending rock layers near Earth’s surface
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Chapter 14
Standardized Test Prep
Multiple Choice, continued
1. The processes of physical weathering and erosion
shape Earth’s landforms by
A.
B.
C.
D.
expanding the elevation of Earth’s surface
decreasing the elevation of Earth's surface
changing the composition of Earth’s surface
bending rock layers near Earth’s surface
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Chapter 14
Standardized Test Prep
Multiple Choice, continued
2. Which of the following rocks is most likely to weather
quickly?
F.
G.
H.
I.
a buried rock in a mountain
an exposed rock on a plain
a buried rock in a desert
an exposed rock on a slope
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Chapter 14
Standardized Test Prep
Multiple Choice, continued
2. Which of the following rocks is most likely to weather
quickly?
F.
G.
H.
I.
a buried rock in a mountain
an exposed rock on a plain
a buried rock in a desert
an exposed rock on a slope
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Chapter 14
Standardized Test Prep
Multiple Choice, continued
3. The red color of rocks and soil containing iron-rich
minerals is caused by
A.
B.
C.
D.
chemical weathering
mechanical weathering
abrasion
erosion
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Chapter 14
Standardized Test Prep
Multiple Choice, continued
3. The red color of rocks and soil containing iron-rich
minerals is caused by
A.
B.
C.
D.
chemical weathering
mechanical weathering
abrasion
erosion
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Chapter 14
Standardized Test Prep
Multiple Choice, continued
4. In which of the following climates does chemical
weathering generally occur most rapidly?
F.
G.
H.
I.
cold, wet climates
cold, dry climates
warm, humid climates
warm, dry climates
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Chapter 14
Standardized Test Prep
Multiple Choice, continued
4. In which of the following climates does chemical
weathering generally occur most rapidly?
F.
G.
H.
I.
cold, wet climates
cold, dry climates
warm, humid climates
warm, dry climates
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Chapter 14
Standardized Test Prep
Multiple Choice, continued
5. Which of the following has the greatest impact on
soil composition?
A.
B.
C.
D.
activity of plants and animals
characteristics of the parent rock
amount of precipitation
shape of the land
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Chapter 14
Standardized Test Prep
Multiple Choice, continued
5. Which of the following has the greatest impact on
soil composition?
A.
B.
C.
D.
activity of plants and animals
characteristics of the parent rock
amount of precipitation
shape of the land
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Chapter 14
Standardized Test Prep
Short Response, continued
6. In what type of decomposition reaction do hydrogen
ions from water displace elements in a mineral?
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Chapter 14
Standardized Test Prep
Short Response, continued
6. In what type of decomposition reaction do hydrogen
ions from water displace elements in a mineral?
hydrolysis
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Chapter 14
Standardized Test Prep
Short Response, continued
7. Sand carried by wind is responsible for what type of
mechanical weathering?
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Chapter 14
Standardized Test Prep
Short Response, continued
7. Sand carried by wind is responsible for what type of
mechanical weathering?
abrasion
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Chapter 14
Standardized Test Prep
Reading Skills
Read the passage below. Then, answer questions 8–10.
How Rock Becomes Soil
Earthworms are crucial for forming soil. As they search for food by digging
tunnels, they expose rocks and minerals to the effects of weathering. Over time, this
process creates new soil.
Worms are not the only living things that help create soil. Plants also play a part
in the weathering process. As the roots of plants grow and seek out water and
nutrients, they help break large rock fragments into smaller ones. Have you ever
seen a plant growing in a sidewalk? As the plant grows, its roots spread into tiny
cracks in the sidewalk. These roots apply pressure to the cracks, and over time, the
cracks become larger. As the plants make the cracks larger, ice wedging can occur
more readily. As the cracks expand, more water can flow into them. When the water
freezes, it expands and presses against the walls of the crack, which makes the
crack larger. Over time, the weathering caused by water, plants, and worms helps
break down rock to form soil.
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Chapter 14
Standardized Test Prep
Reading Skills, continued
8. Which of the following statements can be inferred
from the passage?
A. Weathering can occur only when water freezes in
cracks in rocks.
B. Only large plants have roots that are powerful
enough to increase the rate of weathering.
C. Local biological activity may increase the rate of
weathering in a given area.
D. Plant roots often prevents weathering by filling
cracks and keeping water out of cracks.
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Chapter 14
Standardized Test Prep
Reading Skills, continued
8. Which of the following statements can be inferred from
the passage?
A. Weathering can occur only when water freezes in
cracks in rocks.
B. Only large plants have roots that are powerful
enough to increase the rate of weathering.
C. Local biological activity may increase the rate of
weathering in a given area.
D. Plant roots often prevents weathering by filling
cracks and keeping water out of cracks.
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Chapter 14
Standardized Test Prep
Reading Skills, continued
9. Ice wedging, as described in the passage, is an
example of which of the following?
F.
G.
H.
I.
oxidation
mechanical weathering
chemical weathering
hydrolysis
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Chapter 14
Standardized Test Prep
Reading Skills, continued
9. Ice wedging, as described in the passage, is an
example of which of the following?
F.
G.
H.
I.
oxidation
mechanical weathering
chemical weathering
hydrolysis
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Chapter 14
Standardized Test Prep
Reading Skills, continued
10. What are some ways not mentioned in the passage
in which the activity of biological organisms may
increase weathering?
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Chapter 14
Standardized Test Prep
Reading Skills, continued
10. What are some ways not mentioned in the passage
in which the activity of biological organisms may
increase weathering?
Answers should include: almost any activity initiated by a living
organism that exposes rock and soil to wind or water would be
an acceptable answer; construction by humans breaks up
rocks and creates quarries, which contribute to weathering;
tunneling animals, other than worms, churn and expose rocks
in soil to the surface; rotting vegetation and animal waste may
release acids that can help destroy rocks when the acids are
mixed with groundwater.
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Chapter 14
Standardized Test Prep
Interpreting Graphics
Use the diagram below to answer questions 11 and 12.
The diagram shows the soil profile of a mature soil.
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Chapter 14
Standardized Test Prep
Interpreting Graphics, continued
11. Which of the layers in the soil profile above contains
the greatest number of soil organisms?
A.
B.
C.
D.
layer A
layer B
layer C
layer D
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Chapter 14
Standardized Test Prep
Interpreting Graphics, continued
11. Which of the layers in the soil profile above contains
the greatest number of soil organisms?
A.
B.
C.
D.
layer A
layer B
layer C
layer D
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Chapter 14
Standardized Test Prep
Interpreting Graphics, continued
12. Which two layers in the soil profile above are the
least likely to contain the dark, organic material
humus.
F.
G.
H.
I.
layers A and B
layers B and C
layers C and D
layers A and D
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Chapter 14
Standardized Test Prep
Interpreting Graphics, continued
12. Which two layers in the soil profile above are the
least likely to contain the dark, organic material
humus.
F.
G.
H.
I.
layers A and B
layers B and C
layers C and D
layers A and D
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Chapter 14
Standardized Test Prep
Interpreting Graphics
Use the diagram of stone blocks to answer question 13.
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Chapter 14
Standardized Test Prep
Interpreting Graphics, continued
13. If the blocks shown in diagrams A, B, and C above contain
identical volumes and are made of the same types of minerals,
will they weather at the same rate? Explain your answer.
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Chapter 14
Standardized Test Prep
Interpreting Graphics, continued
13. If the blocks shown in diagrams A, B, and C above contain
identical volumes and are made of the same types of minerals,
will they weather at the same rate? Explain your answer.
Answers should include: the eight small blocks in part C will weather
most rapidly; students should relate the rate of weathering to the
amount of exposed surface area available; students should examine
the diagram and consider that the total surface area of each
rectangular solid, or cube, is equal to the sum of the areas of each of
the cube’s six sides. The block shown in figure A has far less exposed
surface than the blocks shown in figures B or C. If all conditions are
equal, the more surface area that is available to experience
weathering, the faster weathering will occur; even though the figures
show the same volume and type of rock, the blocks of figure C would
weather at the fastest rate due to their larger total surface area. The
blocks of figure A would weather at the slowest rate.
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Chapter 14
Chemical Weathering
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Chapter 14
Surface Area
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Chapter 14
Soil Horizons of Residual Soils
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Chapter 14
Soil Erosion Vulnerability Map
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Chapter 14
Soil Map of North Carolina
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