Constructive and
Destructive Forces
Layers of the Earth
Constructive Forces
Identify surface features caused by destructive forces.
• Construct means to build up.
• Forces that build up features on the
surface of the Earth.
– Sediment (Deltas, sand dunes, etc.)
– Volcanoes (makes Islands)
– Tectonic Plates (Mountains)
– Crust deformation (Folding or Faulting)
Sediment
• The process of sediment being carried
causes 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.
Wind Deposition
Sand Dune Cumberland Island, GA
Water Deposition
Sediment is carried by river
Glacial Deposition
Volcano
• http://app.discoveryeducation.com/search
?Ntt=volcano+erupt
• United Streaming-Fire Down Below
Volcanoes
• 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 surface.
• Volcanic activity involving the extrusion of
rock tends to form mountains or features
like mountains over a period of time.
• Magma (inside)
• Lava (outside)
Volcanoes
• There are two main types of volcanoes: shield
and composite.
• Shield volcanoes are usually found in the middle
of tectonic plates. Islands like Hawaii are good
examples of this type of volcano. These are
making new islands every year…takes a long
time. (Hawaiian Islands)
• There's a hole in the middle of the plate and
magma moves out and piles on top of itself,
slowly building a mountain of rock. (Katmai)
Volcanoes
1. Magma reservoir
2. Country rock
3. Conduit (pipe)
4. Base
5. Sill
6. Branch pipe
7. Layers of ash emitted
by the volcano
8. Flank
9. Layers of lava emitted
by the volcano
10. Throat
11. Parasitic cone
12. Lava flow
13. Vent
14. Crater
15. Ash cloud
HOT SPOT
• http://app.discoveryeducation.com/search
?Ntt=hotspot
• United Streaming-Hot Spot
Tectonic Plates
• Mountains can be formed because of
moving tectonic plates.
Tectonic Plates
Faults
• 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.
Destructive Forces
Identify examples of surface features caused by destructive processes.
• Destruct means to destroy.
• Forces that destroy features on the Earth’s
surface.
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–
–
–
Erosion (water - rivers and oceans, wind)
Weathering (chemical or mechanical)
Impact of organisms
Earthquake
Earthquakes
• An earthquake is a phenomenon that
results from the sudden release of stored
energy in the Earth’s crust.
• It is caused by a strain on the fault lines of
the Earth’s crust. When the energy of the
strain is released, similar to a rubber band
snapping, 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. Earthquake Animation!
Earthquake
Weathering and Erosion
• Weathering is the breakdown of the continents and the
land around you. The breaking down of these rocks and
land due to forces such as wind and water is weathering.
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. If it is moved
elsewhere it is called erosion.
Mechanical Weathering
• Mechanical weathering is the
process of breaking big rocks
into little ones. This process
usually happens near the surface
of the planet. Temperature also
affects the land. The cool nights
and hot days always cause
things to expand and contract.
That movement can cause rocks
to crack and break apart. Roots
and plants also push into the
rocks and break them apart.
They act like wedges and push
the rocks apart. Little animals
also help by burrowing and
digging through the ground.
Chemical Weathering
• Chemical weathering
includes the effect of
weathering on molecules
and atoms. As with all
chemistry, the greater the
surface area of an object,
the more chemical reactions
can take place. For these
chemical reactions to
happen in nature, moisture,
and heat must be present.
Biological Weathering
(Impact of Organisms)
• Biological weathering
would include the effect
of animals and plants
on the landscape. This
is more than roots
digging in and wedging
rocks. Biological
weathering is the
actual molecular
breakdown of minerals.
Earthquakes
• More than buildings collapse
when an earthquake hits. The
land itself is totally changed. You
can see scars across the
landscape. Those scars appear
when one block of land has
moved compared to another.
Roads often change their
placement. They either become
uneven or just crack. Streams
can also change course.
Sometimes rocks can fall and
block the stream. Other times,
the land is even lowered in
certain areas. When it's lower,
it's easier for the water to flow in
the new direction .
Earthquakes
• San Andreas Fault line is 810 miles and
runs along California. It separates the
tectonic boundary of the Pacific and North
America boundary.
Technology and
Human Interventions
• Humans try to CONTROL these forces.
– seismological studies
– flood control (dams, levees, storm drain
management, etc.)
– beach reclamation (Georgia coastal islands)
Seismic Waves
• Scientists study earthquakes so that they can
understand how they work and so that they can try to
predict future quakes.
• Earthquakes are recorded by instruments called
“seismographs”.
• A short wiggly line means a small earthquake and a
large one means a large earthquake.
Seismic Waves
• These are waves of energy that travel
through Earth’s layers studied by
geologist.
• Primary (P waves) travel fast
• Secondary waves (S waves) travel
through solids
Flood Control
Lake Allatoona was
created in 1950 by the
U.S. Army Corps of
Engineers for flood
control. At more than
12,000 acres, Allatoona is
one of the larger lakes in
the state.
• The U.S. Army Corps
of Engineers began
constructing dams in
Georgia for navigation
and flood control in the
1940s and 1950s under
the Flood Control Act of
1944 and the
Watershed Protection
and Flood Prevention
Act of 1954.
Flood Control Methods
• Dams control the water
flow in a stream or river.
• A levee is an
embankment designed to
prevent the flooding of a
river.
• Storm drains are for
carrying off rainfall
drained from paved
surfaces, roofs, etc.
Beach Reclamation
• Weather, waves and wind cause the
coastline to wash away.
• Keeping sand dunes intact helps to keep
the beaches from eroding.
Stone Mountain
formed by plate tectonics
Emerson fault
Gorge
Providence Canyon, GA
Appalachian Mountains
Sand Mountain
Lime sinks-chemical dissolution
of rocks
Pine Mountain
Chain Rock and KY first state
park
Cumberland Falls
Only Falls with Moonbow
Beaches
Brasstown Bald
highest natural point in GA
Brevard Fault Zone
Cumberland Plateau
Lookout Mountain
last battle of Cherokees
Blue Ridge Mountains
Mississippi River
largest drain in USA