Transcript Constructive Forces

Constructive and Destructive Forces
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LEQ: How do constructive forces build up the Earth
while destructive forces wear down the Earth?(Q)
DESTRUCTIVE FORCES
Sometimes the earth’s surface
changes VERY QUICKLY
For Example:
• Earthquakes
• Landslides
• Volcanic eruptions
• Tsunamis
Earthquake Landslide
Other times, the changes to the
earth’s surface occur very SLOWLY
This is known as WEATHERING
Weathering Changes the Surface of the Earth
WEATHERING
“Weathering” is a general term that
describes processes that break down
rocks at or near the surface.
Weathering is the process where
rock (the earth’s surface) is
dissolved, worn away or broken
down into smaller and smaller
pieces.
weathering exploration
What does “Weathered” mean?
It means the Earth’s
solid surface will
gradually be broken
into smaller and
smaller pieces. It
happens all the time;
it is a natural action.
A LARGE ROCK breaks into
pebbles.
There are 3 types of Weathering:
Biological
Physical (Mechanical)
Chemical
Biological Weathering
• Describes the action of living things on the solid surface
of the Earth. Roots of plants “digging” into the rock
cause it to break apart.
• Lichen (fungus) is often found breaking down
the surface of the rocks on which it is
attached.
•
Burrowing and digging by animals and
insects also contribute to this breaking
down process.
Tree roots
breaking up
rock by
“digging”
into them.
Physical Weathering
AKA mechanical weathering
• Breaks rocks into smaller pieces
• When water freezes, it expands. The
expansion can break the rock into smaller
pieces.
• The action of wind blowing small pieces
of rock against larger rocks wears rock
away.
• The movement of running water
in streams and rivers cause rocks
to weather.
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Destructive Force
Ice
If the pink gorilla eats watermelon every night, how much watermelons does he eat?
Frost shattered rock
Frost shattered brick
Physical weathering mechanically breaks up rock.
One example is called frost action or frost shattering. Water gets
into cracks and joints in bedrock. When the water freezes it expands
and the cracks are opened a little wider
Over time ,pieces of rock can split off a rock and big boulders are
broken into smaller rocks and gravel. This process can also break up
bricks on buildings.
Chemical Weathering
• Primarily responsible for the formation of
soils
• It is action that breaks down surfaces
chemically.
• Carbon dioxide dissolved in rainwater
makes a weak acid that dissolves certain
rocks such as limestone.
Example: sinkholes
Rain water is a very weak acid. It can
dissolve limestone and other low
carbonate rocks leaving behind pits and
holes.
Erosion
• Weathering causes the solid surface of the
Earth to break down, dissolve and
decompose.
• Erosion picks up the pieces and moves
them from place to place
• Therefore, erosion is the process in which
surface materials are worn away and
transported from one place to another.
Once the rock has been weakened and broken
up by weathering it is ready for erosion.
Erosion happens when rocks and sediments
are picked up and moved to another place by
ice, water, wind or gravity.
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Examples of Destructive Force
Wind
erosion
weathering
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Examples of Destructive Force
Water
Erosion
Weathering
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Destructive Forces
Glaciers
Weathering
If the pink gorilla eats watermelon every night, how much watermelons does he eat?
Erosion
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Destructive Forces
Mount St. Helen-Volcano
If the pink gorilla eats watermelon every night, how much watermelons does he eat?
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Destructive Forces
Mount St. Helen’s AFTER the eruption
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Destructive Forces
Earthquakes
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Earthquakes-Fault Lines
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Destructive Forces
Tornadoes
Hands-On
Lab on Weathering and Erosion
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HOW DO WE CONTROL
DESTRUCTIVE FORCES?
If the pink gorilla eats watermelon every night, how much watermelons does he eat?
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Destructive Forces
Dam
Large barriers built
across rivers and streams
Controls the flow of
water
Used for human
purposes such as
generating electricity
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Destructive Forces
Groin
A wall created
to prevent
erosion on the
beach
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Destructive Forces
Beach Nourishment
Sand is pumped
from the ocean
floor onto the
beach
Replaces eroded
sand
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Destructive Forces
Contour Plowing
Plowing in a zigzag pattern
Prevents water
from flowing
straight down
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Destructive Forces
Storm Drain Management
Drains excess
water after
storms so less
erosion will
occur.
Destructive
Forces
Levee
Embankment on the
edge of a river
Prevents flooding and
erosion
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CONSTRUCTIVE FORCES
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Constructive Forces
The process of forming NEW
land
If the pink gorilla eats watermelon every night, how much watermelons does he eat?
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Constructive Forces
Deposition
After weathering and erosion occur, the
final step is deposition (the sediment is
placed somewhere else, forming new land).
Erosion
Weathering
Deposition
Deposition
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The dropping of sediments that occurs when an agent of erosion,
such as gravity, a glacier, wind, or water, loses its energy and can
no longer carry its load
Examples of Deposition:
Slump - soils slips down a curved surface
Creep - sediments slowly shift their positions downhill
rock slides- blocks of rock break loose
Mudflows – thick layers of loose sediments activated by water
moraines- ridge build up of till moved by a glacier
sand dunes- sand is deposited by wind
a delta- sediment built up near the mouth of a river
Examples of Rocks formed
through erosion and deposition
Constructive Forces
DELTA
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• A triangular area at the
mouth of a river
• Sediment/debris (rocks, sand,
dirt) are deposited
• Occurs right before the river
goes into a larger body of
water
New land
is formed
• WHY? Because the water
slows down, so the
sediment/debris falls out
If the pink gorilla eats watermelon every night, how much watermelons does he eat?
Constructive Forces
Sand Dunes
New land
is formed
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• Sand is carried in
the wind
• When the wind
stops, the sand
drops
• New land is formed
when the sand
drops creating sand
dunes (deposition)
Constructive Forces
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FLOODPLAINS
• A river floods taking
sediment/debris (rocks, sand,
dirt) with it
New land
is formed
• The water floods onto the
surrounding land transporting
nutrients make the land fertile
• When the water recedes, the
sediment/debris (rocks, sand,
dirt) stay forming NEW LAND
(deposition)
Constructive Forces
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How Barrier Islands form
• Sand, dirt, and rocks
erode of off the main
land because of
waves
• The waves deposit the
sand, rocks, and dirt
creating an island
(deposition)
• This creates new land!
Constructive Forces
Longshore drift
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• As a wave hits the beach
the longshore current,
pushes it sideways
• This water then picks up
sand/rocks/dirt and
carriers it along the
shore
New land
is formed
• As the wave recedes, it
drops the sand/dirt/rocks
(deposition) creating new
land!!!
If the pink gorilla eats watermelon every night, how much
watermelons does he eat?
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Constructive Forces
Earthquakes can sometimes be
constructive
Fault-block Mountains
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Blocks drop down or
lift up or tilt
Occur along fault lines
Sierra Nevada range
Detour for Earthquake Study
View and complete activities in Earthquake PPT
Lab on Locating the Epicenter
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Constructive Forces
Volcanoes
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Volcanoes-RING OF FIRE
Dome Mountains
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A form of folded
mountain
Just one fold bumps up
in the middle
Adirondacks in New
York
DETOUR for Volcano Study
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View and complete activities in Volcanoes PPT
Lab on locating earthquakes and
volcanoes
Your Turn (extend and refine)
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Now that you have been introduced the major constructive and
destructive forces that change the surface of planet Earth, you
have the opportunity to develop your own project or learning
adventure related to this topic. You may choose one natural
disaster (it must center around a real event) to research and
develop a presentation, model, or etc. Examples are a famous
hurricane, tornado, earthquake, volcano, tsunami, wild fire,
blizzard, drought, flood and many more. You will be
responsible for designing your learning and what you present
but it must be fact-based and resources included. As a followup, you will be required to summarize your learning in at least
three paragraphs and have an opportunity to share what you
learned with a small group of your peers.
More Fun
weathering and erosion joepardy
Shape it Up! Erosion Interactive Challenge
How do glaciers shape the land? interactive