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Changes to Earth’s
Layers of the Earth
Constructive vs. Destructive
Constructive Forces build
up features on the surface of
the Earth.
Mt. Everest
Destructive Forces break
down features on the Earth’s
Niagra Falls
Destructive Forces
Identify examples of surface features caused by destructive processes.
• Destruct means to destroy or break down.
• Examples…
Weathering (chemical or mechanical)
Erosion (water - rivers and oceans, wind)
Impact of organisms
Destructive Force: Weathering
The process of breaking down of rocks and land due to forces
such as gravity, wind, water and ice. When it rains, rocks are
washed down a mountain or down a stream. Soils are washed
away. The ocean beats against a cliff and breaks it apart. Wind
causes rock to wear away as it blows sediment through the air.
Destructive Force: Erosion
When rocks and sediment weather and move elsewhere, this
movement is called erosion. The process is caused by water,
ice, wind or gravity moving pieces of rock and soil.
Destructive Force:
Mechanical Weathering
Mechanical weathering (physical weathering) is the process
of breaking rock and sediment into smaller pieces. For
• Temperature…cool nights and hot days causes water in
the rock to expand and contract
• Flowing rivers and streams
• Roots and plants also pushing into the rocks
• Animals burrowing and digging
Destructive Force:
Mechanical Weathering
from Flowing Water
When water in
rivers, streams,
and waterfalls
move over rock it
breaking into
smaller and
smaller pieces.
Destructive Force: Erosion
from Flowing Water
Rivers, streams, and runoff carry weathered rock or soil to
another place. Fast moving streams and rivers will carry big
and small rocks downstream. Slower moving water carries
smaller rocks and soil downstream. This moving water causes
soil erosion—carrying the soil away to a different location.
Destructive Force: Erosion
from Flowing Water forms Canyons
Canyons are large valleys created by a river or stream. This simple
animation shows how the Colorado River has "cut down" into the
rock layers of the Grand Canyon, creating a deep valley wit steep
walls. This is created over thousand of years. Canyons demonstrate
both weathering and erosion.
Destructive Force:
Mechanical Weathering and Erosion
due to Gravity
As rocks
slide down a
hill or
they break
other rocks
into smaller
Destructive Force:
Mechanical Weathering and Erosion
from Water and Gravity
Sometimes a side of the hill is
washed away by running water
after a lot of precipitation. The
soil and rocks move down the hill
in a landslide or mudslide. Watch
this landslide in the Alps…
Watch Mt. St. Helens Erupt on
May 18th, 1980…
Destructive Force: Mechanical
Weathering and Erosion
from Water and Gravity
Destructive Force:
Mechanical Weathering and Erosion
by Wind
As the wind blows it
picks up small
particles of sand and
blasts large rocks
with the abrasive
particles, cutting and
shaping the rock.
More Mechanical Weathering and
by Wind
Strong winds can move small rocks and soil from one
location to another. Blowing wind and sand are the reasons
these rocks and dunes have formed.
Destructive Force:
Mechanical Weathering and Erosion
From Water and Ice
Water in cracks in the rock freezes. As it freezes it expands
causing the rocks to break. This is known as ice wedging.
Destructive Force:
Mechanical Weathering and Erosion
From Wind,
Water, and Ice
Land is being
constantly worn
down by wind,
water, and ice.
The original
level of the
Destructive Force:
Mechanical Weathering and Erosion
by Glaciers (Ice)
Glaciers are formed over
many years as large amounts
of snow fall and accumulate.
The snow compacts and
changes to ice. Stuck in the
bottom of the glacier are
stones of various sizes that
wear away the rock under the
glacier as it moves downhill.
It is considered a large river
of ice that moves very slowly
Destructive Force:
Mechanical Weathering and Erosion
by Glaciers (Ice)
Striations or scratches
made in the rock under
a glacier by the stones
stuck in it as the glacier
moved downhill. Click
on the link…
Destructive Force:
Mechanical Weathering and Erosion
by Glaciers (Ice)
The weathering and
erosion from glaciers
create large U-shape
valleys, which take
thousands of years to
create. Watch this
glacier weather and
erode the land over
Destructive Force:
Mechanical Weathering and Erosion
By Plants and Animals
Plant roots break apart rocks.
Animals burrow breaking up and
moving rock and sediment.
Destructive Force:
Chemical Weathering
Chemical weathering includes
the effect of weathering on
molecules and atoms. For
these chemical reactions to
happen in nature, moisture,
and heat must be present.
Water, oxygen, carbon, and
other chemicals in the
atmosphere are the main
reasons for chemical
Destructive Force:
Chemical Weathering
Due to Acid Rain
Destructive Force: Chemical
Due to Plants and Animals
Chemical weathering would
include the effect of animals
and plants on the landscape.
This is more than roots
digging in and wedging rocks.
This is also considered
biological weathering, which
is the actual molecular
breakdown of minerals.
Destructive Force:
Mechanical and Chemical Weathering
Destructive Force: Earthquakes
An earthquake results from the sudden
release of stored energy in the Earth’s
It is caused by a strain on the fault lines of
the Earth’s crust. When the energy of the
strain is released, the earthquake occurs.
At the Earth's surface, earthquakes cause a
shaking or displacement of the ground and
sometimes cause the ground to break apart
and change shape. Transforming and
converging boundaries often result in
destructive changes to Earth’s surface.
Earthquake Animation!
Destructive Force: Earthquakes
Destructive Force: Earthquakes
Not only do buildings collapse when an earthquake hits, but the
land itself changes. Visible changes appear when one block of
land has moved compared to another. Roads often change
their placement by becoming uneven or cracked. Streams can
also change course. Sometimes rocks fall and block a stream.
Other times, the land is lowered in certain areas which makes it
easier for the water to flow in the new direction.
Destructive Force: Earthquakes
The San Andreas Fault
line is 810 miles and runs
along California. It
separates the tectonic
boundary of the Pacific
and North America
boundary. They are
transforming boundaries.
Constructive Forces
Identify surface features caused by constructive forces.
• Construct means to build up.
• Constructive Forces build up features on
the surface of the Earth.
– Sediment (Deltas, sand dunes, etc.)
– Tectonic Plates Colliding (Mountains)
– Crust deformation (Folding or Faulting)
– Volcanoes (makes Islands)
Constructive Force:
Deposition of Sediment
• The process of sediment being carried and
deposited , which creates new landforms.
– Wind – sand transported by the wind creates
sand dunes.
– Water – bits of soil and rock can be carried
downstream and deposited causing deltas.
– Ice – glaciers pick up and move rock and
other materials, depositing it elsewhere.
Constructive Force:
Deposition of Sediment
By Wind
Sand is carried and deposited creates a sand dune.
Constructive Force:
Deposition of Sediment
By Water
Amazon River Delta into the
Atlantic Ocean
Mississippi River Delta into the
Gulf of Mexico
Sediment is carried and deposited at the mouth of a river
creates a delta.
Constructive Force:
Deposition of Sediment
By Glaciers (Ice)
Constructive Force:
Tectonic Plates
Mountains and ridges can be formed because
of moving tectonic plates. Watch this…
Constructive Force:
Tectonic Plates
The Rockies, Andes, and
Himalayas Mountain Ranges
formed from plates colliding. This
is called a convergent boundary.
Constructive Force:
Tectonic Plates
Mid-Atlantic Ridge or the
Great Rift Valley form from
plates separating. This is
called a divergent boundary.
Constructive Force:
Faults and Folding
Faults are cracks in the Earth’s crust. The
surface of the Earth is made up of tectonic
plates that are floating on magma (molten
rock). It is along these fault lines that
earthquakes and volcanoes occur.
Constructive Force:
• A volcano is an opening in
the Earth's surface or crust,
which allows hot, molten
rock, ash and gases to
escape from deep below the
crust of Earth’s surface.
• Volcanic activity form
mountains and land over
• Magma hot molten rock
within volcano. Lava flows
from the volcano on Earth's
surface. It cools to form
igneous rock.
Constructive Force:
• There are two main types of
volcanoes: shield and
• Shield volcanoes are usually
found in the middle of tectonic
plates. Magma moves out a
hole in the middle of the plate
piling lava on Earth’s surface,
and slowly building a mountain
of rock. Ex. Hawaiian Islands
• Composite volcanoes erupt
less often and are more violent
when they do erupt. Ex. Mt. St.
Constructive Force:
Constructive Force:
Constructive vs. Destructive
• What are two examples of destructive
forces? Give an example of a slow and fast
destructive force.
• What are four examples of constructive
forces? Give an example of a slow and fast
destructive force
• Give an example where constructive and
destructive forces work together to create a