Erosion and Weathering
Effects of Erosion
• Title page “Effects of Erosion”
• For each before and after picture, write
your observations of what has changed
and your hypothesis (what caused it to
change).
Solve the Mystery of the
Great Sphinx of Giza:
• Observation: What is different about the
Ancient Egyptian Sphinx in the two
images?
• Hypothesis: What do you think caused this
difference?
Before:
Great Sphinx
Observations:
Hypothesis:
After:
Sphinx Mystery Uncovered:
• The head was made up of a harder strata—so it
avoided a lot of weathering. (its nose was taken
off by soldiers in the 18th century.
• The body was made out of softer limestone
(what kind or rock is this?
• Some weathering by wind
and sand and dust has
occurred.
• However, it is believed that
flooding from the Nile River
led to extreme water erosion.
After:
Solve the Mystery of
The Grand Canyon:
• Observation: What is different about the
Grand Canyon in the two images?
• Hypothesis: What do you think caused this
difference?
Before:
Grand Canyon
Observations:
Hypothesis:
After:
Grand Canyon Mystery Uncovered:
• Carved out (eroded) by the Colorado River over
the past 17 million years.
After:
Solve the mystery of the
Statue of Liberty
• Observation: What is different about the
Statue of Liberty in the two images?
• Hypothesis: What do you think caused this
difference?
Before:
Statue of Liberty
Observations:
Hypothesis:After:
Statue of Liberty Mystery Uncovered:
• The statue of liberty is
made of copper (like a
penny) over time it is
being oxidized by water
and air– a form of
chemical weathering—
making it green instead of
silver.
Solve the mystery of the
landscape:
• Observation: What is different about the
landscape in the two images?
• Hypothesis: What do you think caused this
difference?
Before:
Landscape
Observations:
Hypothesis:
After:
Landscape Mystery Uncovered:
• Glaciers carve through
plateaus, mountains and
land easily, causing
weathering and erosion
•
1970s:
Sandcastle
Observation:
Hypothesis:
Today:
1990s:
Castle Mystery Uncovered:
• The largest “active”/ “living”
Sand Dune on the East
Coast—Jockey’s Ridge
North Carolina
• The amount of sand making
up the 420 acres of
Jockey's Ridge is equal to
about 6,000,000 dump
truck loads!
• The Sand is mostly quartz
rock which came from the
mountains millions of years
ago.—what kind of rock is
quartz rock?
Castle Mystery
Uncovered:
• Each year winds from each
directions erode the Dune,
picking up sand and moving.
• Over time the Dune moved so
much it covered an old Putput coarse—which the castle
was part of.
• Over more time the Dune
moved so much that it is
uncovering the Put-put coarse
and unveiling a
weathered/eroded castle—
wind and sand weathering.
Erosion
1. Erosion is the natural moving of
material from one place to another.
2. Mountain rivers
can form Vshaped rivers
and canyons.
3. It takes a river millions of years
to create a valley or canyon.
• We can see from the examples, dirt and
soil can be eroded and change
landscapes. What typically needs to
happen to the rock before it is eroded?
– It needs to be weathered!
Mechanical Weathering
Mechanical— when a rock
is broken into smaller
pieces —doesn’t change
the chemical composition
of the rock
Examples:
-- Grand Canyon, carved out by the Colorado River—no
change of the rock just denting the rock or changing its
shape
-- Sphinx of Giza—sand and water both chipped away at the
Sphinx changing its shape but not what it was made of.
Think of sand paper or breaking/cracking something!
Types of Mechanical Weathering
• Abrasion: When rocks move (erode), they
collide with each other and break apart
• Expansion and Contraction: Heating
and cooling causes rock to swell and
shrink and crack
• Frost action: Water fills cracks, and then
expands when it freezes
• Plants and animals: Plants wedge in
rocks, animals tunnel and dig
Chemical Weathering
Chemical--when a rock is broken
down through a chemical change
Examples:
--Statue of Liberty, tarnished/ rusted by the air and water
exposure and turned green
--Rusting of a bicycle
-- Acid Rain can erode statues, gravestones etc.
Think of changing
the entire rock!
Types of Chemical Weathering
• Hydrolysis: Hydrogen in water reacts with
minerals, creating new compound
• Carbonation: Acid in water causes the
rock to dissolve
• Oxidation: The chemical reaction of
oxygen with other substances (rust)
Soil
http://www.brainpop.com/science/earthsystem/s
How is soil created?
How is soil created?
1. Exposed rock
(“bedrock”) starts
to be weathered.
2. Wind, moving
water, changes in
temperature
continue the
weathering and
erosion process.
3. Broken pieces get
broken down
further and further
How is soil created?
3. Animals & plants
aerate the soil and
decompose organic
matter.
4. Bacteria and fungi
grow and produce
acids that further break
down rock—producing
minerals and nutrients
for plants.
Soil
Loose surface of the earth—
made up of rock, decayed
plants and animals, air,
minerals, water
– Soil types change due to
different size mineral particles
such as sand, silt and clay
What does soil look like?
Soil Horizons
• A Horizon—topsoil
• B Horizon—subsoil
• C Horizon—
weathered bedrock
• D Horizon—
unweathered bedrock
Digging up the Horizons
A-horizon =
B-horizon =
=
=
=
=
C-horizon =
=
D-horizon =
A Horizon- Topsoil
• Nutrient Rich
• Usually dark to light
brown
• Made up of fine particles
of weathered rock &
humus

Humus
• Dark organic (living) material
made of dead, decaying plant
and animal matter
B Horizon Subsoil
• Often red or brown
• Clay, iron oxides
and dissolved
minerals washed
down from AHorizon
• Deep roots found in
this layer

C Horizon
• Partially weathered
rock material (rock
fragments)

D Horizon
• Bedrock
• Un-weathered
rock material
Exit Ticket:
1.What is soil and how does it form?
2.What are the 4 horizons (layers) of the
soil and what are they made of?
A
B
C
D
?
12.12 Warm-Up
1. Organic matter in soil is made from —
A. Weathered parent rock
B. Decayed plants and animals
C. Acid Rain
D. Carbon Dioxide
2. The formation of a soil is influenced by all BUT one of the factors
listed. That factor is
A) climate.
B) parent rock.
C) the partial melting of local granite.
D) biologic activity of plants and animals.
3. What is the process by which organic matter breaks down to become
part of the soil?
A) compaction
B) decomposition
C) erosion
D) weathering
Let’s Hear A Little About
Human Impact –
Video!
Human Impact on Soil and Erosion
• Human Activity is the main force of
speedy (accelerated) erosion.
• Land-Use Practices that remove plants
from an area increase erosion because the
plant roots hold down the soil and prevent
it from being washed or blown away
1. Farming (plowing and over-grazing)
2. Construction and Development
3. Mining
Farming
• Over-grazed (by animals) or overplowed (by humans) soil will be less
fertile and will most likely be carried
away by water and wind
• Plants help in reducing soil erosion by
holding the soil in place
Construction and Development
• People dig away soil to make roads, houses,
or other buildings
• The soil can be washed or blown away
because it’s plant cover has been removed
(no roots to hold it down).
• Sediment often goes into rivers, streams or
lakes
– This can harm organisms, flood rivers, and fill up lakes
Mining
• Digging of mines involves the removal of
plants and soil from the surface of the ground
• Rocks and minerals are then exposed to the
air and rainwater, which speeds up chemical
weathering
Solutions
• Conservation Tillage: Reducing the
number of times fields are plowed
• Crop rotation: Planting different crops in
different years makes soil more fertile
• Fences/Windbreaks: Fences or rows of
trees around fields can prevent soil from
being eroded by wind
• Terraces: Flat, step-like areas built on hills to
stop the soil from eroding down the hill
Scavenger Hunt