Erosion, Deposition, Weathering, and Mass Movement in Geology
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EROSION & DEPOSITION
The creation of
sedimentary rocks
WEATHERING AND MASS MOVEMENT
Objectives:
1. Describe the processes by which
erosion wears down and carries away
rock
2. Distinguish between chemical and
mechanical weathering
3. Describe the factors that affect the
rate of weathering
4. Explain how the force of gravity
contributes to erosion by mass movement
EROSION
Definition: erosion is the process that
wears
down
and carries away rock and
soil
Erosion is associated with movement from
one place to another
Erosion acts through weathering, the
force of gravity, and through movement
of streams, groundwater, glaciers, wind
and waves
Erosion breaks down the tallest mountains
over time
WEATHERING
Definition: weathering is the process by
which rocks are chemically altered or
physically broken down into fragments
at or near Earth’s surface
There are 2 types of weathering:
mechanical and chemical
Both processes cause rocks to
disintegrate and decompose
Definition: mechanical weathering is
the process of physically breaking rock
into smaller fragments
Definition: frost wedging is physical
weathering due to water seeping into
cracks and expanding due to
freezing
Many road potholes are the result of
frost wedging
Definition: abrasion is physical
weathering caused by the process
that occurs when rocks scrape or
grind against each other
This can occur by water or wind
Plant roots cause physical weathering
by growing into cracks breaking rocks
apart
Erosion causes physical weathering
by removing material from the
surface of the rock, releasing pressure
on the rock causing the outside to
crack and flake
Definition: chemical weathering in a
process in which rock is broken down
by chemical reactions
Water is the main reactant in
chemical weathering
Chemical reactions dissolve the
minerals that make up the rocks or
changes them into new materials
Water and carbon dioxide combine
to form carbonic acid producing acid
rain
Acid rainwater dissolves many
minerals
Rusting, which is a kind of oxidation,
occurs in minerals that are rich in iron
FACTORS THAT AFFECT THE RATE OF
WEATHERING
There are 3 main factors that determine how
fast mechanical and physical weathering
take place
They are temperature, availability of water
and the type of rock
Certain rocks like limestone and marble
undergo rapid chemical weathering since
their main mineral (calcite) dissolves in water
Slate, quartz and mica are more resistant to
chemical change
MASS MOVEMENT
Definition: mass movement is the
downward movement of rock and soil
due to gravity
Definition: the rapid movement of large
amounts of rock and soil is a landslide
Landslides often happen after heavy rain
Definition: mudflow is rapid mass
movement of soil & other sediment with
water
After rain water loosens the sediment,
increases its weight and causes it to flow
Definition: creep is the gradual
slowing down of soil that is moving
down a slope
Creep usually occurs due to ice
Creep happens so slowly is often
hard to notice
Definition: slumping occurs when
weak layers of soil or rock move
downslope as a single unit
Gravity acting on water saturated
soil and rock causes slumping
WATER SHAPES THE LAND
Objectives:
1. Explain how running water
erodes the land
2. Identify features formed by
erosion and deposition due to
running water
3. Describe how caves and
sinkholes are formed by
groundwater erosion
RUNNING WATER & EROSION
Definition: deposition is the process in which
sediment is laid down in new locations
Deposition is a type of erosion
Most sediment is moved by running water
Running water erodes the land
Definition: saltation is the process of particles
bouncing along a stream bottom
A large amount of deposition with a fast
moving water source increases erosion
Speed increases a streams ability to erode
FEATURES FORMED BY EROSION
Water erosion form v-shaped valleys, waterfalls,
meanders and oxbow lakes
Near its source the stream moves fast, causes
valley’s sides to become steeper & sharply angled
creating a V
V-shaped valleys can contain rapids and
waterfalls
Waterfalls develop where a stream crosses rock
layers that differ in hardness
The harder layers resist erosion for the top of the
waterfall while the other layers are worn away
creating the cliff over which water tumbles
Definition: a flood plain is the flat area
along a stream that is entirely
covered only during times of flood
During flooding, erosion may further
widen the valley
Definition: a meander is a looplike
bend in the river caused by sediment
being deposited on the outside of a
curve in the river
Features deposited by flowing water
include alluvial fans and delta
Definition: an alluvial fan is sediment
that has settled out as the stream
flows out of the mountains creating a
fan-shaped deposit
Definition: a delta is mass of sediment
that was carried & deposited by a
stream that flows into a lake or ocean
where the water slows down
The delta is located where a river
enters a large body of water
GROUNDWATER EROSION
The processes of chemical
weathering causes groundwater
erosion including the formation of
caves and sinkholes
Acid rain moves through the ground
reacting with some rocks
Limestone easily erodes away forming
caves and caverns
Sometimes water drips into the
cavern from rock layers above
Definition: a stalactite is an icicle-like formation of
minerals created from water dripping from the
ceiling of the cave
Definition: a stalagmite is a pillar of minerals
created from water dripping down to the floor
Definition: a sinkhole is an entire portion of ground
that has collapsed due to erosion weakening a
layer of limestone
Areas of southern and central US have many
sinkholes
EXAMPES OF SEDIMENTARY ROCK
• The three types of rocks created by the rock cycle are igneous, metamorphic and sedimentary
• Metamorphic rocks are created by heat & pressure, while igneous are primarily created by melting solid rock into liquid rock called magma, & then cooling that rock either above or below ground
• In the rock cycle, sedimentary rocks are created by weathering, erosion, cementation and compaction
• This PPT discusses the erosion aspect of sedimentary rock creation
• Erosion often involves water
• Water will erode the land and it will change the shape of the land
• This PPT explains how water, which is a surface process, participates in this aspect of the rock cycle
Explore the processes of erosion, deposition, weathering, and mass movement in geology. Learn about how rocks are broken down and carried away, the different types of weathering, and the factors affecting these processes. Discover the role of gravity in erosion and the impact of chemical reactions on rock formations.
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Presentation Transcript
EROSION & DEPOSITION The creation of sedimentary rocks
WEATHERING AND MASS MOVEMENT Objectives: 1. Describe the processes by which erosion wears down and carries away rock 2. Distinguish between chemical and mechanical weathering 3. Describe the factors that affect the rate of weathering 4. Explain how the force of gravity contributes to erosion by mass movement
EROSION Definition: erosion is the process that wears down and carries away rock and soil Erosion is associated with movement from one place to another Erosion acts through weathering, the force of gravity, and through movement of streams, groundwater, glaciers, wind and waves Erosion breaks down the tallest mountains over time
WEATHERING Definition: weathering is the process by which rocks are chemically altered or physically broken down into fragments at or near Earth s surface There are 2 types of weathering: mechanical and chemical Both processes cause rocks to disintegrate and decompose Definition: mechanical weathering is the process of physically breaking rock into smaller fragments
Definition: frost wedging is physical weathering due to water seeping into cracks and expanding due to freezing Many road potholes are the result of frost wedging Definition: abrasion is physical weathering caused by the process that occurs when rocks scrape or grind against each other This can occur by water or wind
Plant roots cause physical weathering by growing into cracks breaking rocks apart Erosion causes physical weathering by removing material from the surface of the rock, releasing pressure on the rock causing the outside to crack and flake Definition: chemical weathering in a process in which rock is broken down by chemical reactions
Water is the main reactant in chemical weathering Chemical reactions dissolve the minerals that make up the rocks or changes them into new materials Water and carbon dioxide combine to form carbonic acid producing acid rain Acid rainwater dissolves many minerals Rusting, which is a kind of oxidation, occurs in minerals that are rich in iron
FACTORS THAT AFFECT THE RATE OF WEATHERING There are 3 main factors that determine how fast mechanical and physical weathering take place They are temperature, availability of water and the type of rock Certain rocks like limestone and marble undergo rapid chemical weathering since their main mineral (calcite) dissolves in water Slate, quartz and mica are more resistant to chemical change
MASS MOVEMENT Definition: mass movement is the downward movement of rock and soil due to gravity Definition: the rapid movement of large amounts of rock and soil is a landslide Landslides often happen after heavy rain Definition: mudflow is rapid mass movement of soil & other sediment with water After rain water loosens the sediment, increases its weight and causes it to flow
Definition: creep is the gradual slowing down of soil that is moving down a slope Creep usually occurs due to ice Creep happens so slowly is often hard to notice Definition: slumping occurs when weak layers of soil or rock move downslope as a single unit Gravity acting on water saturated soil and rock causes slumping
WATER SHAPES THE LAND Objectives: 1. Explain how running water erodes the land 2. Identify features formed by erosion and deposition due to running water 3. Describe how caves and sinkholes are formed by groundwater erosion
RUNNING WATER & EROSION Definition: deposition is the process in which sediment is laid down in new locations Deposition is a type of erosion Most sediment is moved by running water Running water erodes the land Definition: saltation is the process of particles bouncing along a stream bottom A large amount of deposition with a fast moving water source increases erosion Speed increases a streams ability to erode
FEATURES FORMED BY EROSION Water erosion form v-shaped valleys, waterfalls, meanders and oxbow lakes Near its source the stream moves fast, causes valley s sides to become steeper & sharply angled creating a V V-shaped valleys can contain rapids and waterfalls Waterfalls develop where a stream crosses rock layers that differ in hardness The harder layers resist erosion for the top of the waterfall while the other layers are worn away creating the cliff over which water tumbles
Definition: a flood plain is the flat area along a stream that is entirely covered only during times of flood During flooding, erosion may further widen the valley Definition: a meander is a looplike bend in the river caused by sediment being deposited on the outside of a curve in the river Features deposited by flowing water include alluvial fans and delta
Definition: an alluvial fan is sediment that has settled out as the stream flows out of the mountains creating a fan-shaped deposit Definition: a delta is mass of sediment that was carried & deposited by a stream that flows into a lake or ocean where the water slows down The delta is located where a river enters a large body of water
GROUNDWATER EROSION The processes of chemical weathering causes groundwater erosion including the formation of caves and sinkholes Acid rain moves through the ground reacting with some rocks Limestone easily erodes away forming caves and caverns Sometimes water drips into the cavern from rock layers above
Definition: a stalactite is an icicle-like formation of minerals created from water dripping from the ceiling of the cave Definition: a stalagmite is a pillar of minerals created from water dripping down to the floor Definition: a sinkhole is an entire portion of ground that has collapsed due to erosion weakening a layer of limestone Areas of southern and central US have many sinkholes
