Transcript comprehensive-powerpoint-on-constructive-and

The state of Georgia
wants you to…
• Identify surface features
caused by constructive and
deconstructive processes.
Constructive vs. Destructive
• Land forms are the result of a
combination of constructive and
destructive forces. Constructive
forces affect the earth's surface by
building it up to form new landforms
like mountains and islands.
Destructive forces affect the
earth's surface by breaking down
landforms to form new ones.
Erosion
• Erosion is a process in
which rock and soil are
broken loose from the
earth's surface at one
location and moved to
another
Water Erosion
• Moving water (like a stream) is
an important agent in the
erosion process. Dirt and
other sediment get in the
water and then the moving
water moves it to a new
location.
• Gravity plays an important
role as well in erosion; gravity
pulls down dirt and other
sediments from the hills and
causes erosion.
Wind Erosion
• Wind erosion occurs mostly in flat,
dry areas and close to bodies of
water. Wind erosion removes the
most fertile part of soil and lowers
the soil production. That means most
crops and plants will not make it to
harvest time. All that is left after
wind erosion in soil is the clayish soil
and silts.
• In the 1930s a long dry spell got bad
enough it turned into dust storms.
They called it the Black Blizzards and
it became known as the Dust Bowls.
• Want to know more? Click here
Weathering
• Weathering is the process of
decomposition or disintegration of
rocks and their minerals. That is why
it is considered a destructive force.
The rocks and their minerals break
down into smaller pieces like silt, clay
and sand.
• The weathering process occurs at or
near the surface of the earth. In
fact, the soil we depend on for much
of our food is a mixture of bits and
pieces of weathered rock.
Weathering and Water
• One of the major
causes of weathering
is water. Moving
waters such as rivers
and oceans can
permanently change
the Earth's surface.
The waters and rivers
can carve deep
canyons or weather
cliffs along the
seashore causing them
to fall into the waters.
• Rain water can also cause weathering.
As it rains, rain water can seep into
holes and cracks in rocks causing
weathering and if this water freezes
inside the rock, this can cause the
rock to break into smaller pieces.
Extreme Heat
• Extreme heat is an example of weathering
that can cause destructive changes to the
surface of the earth.
• Rocks that become heated at the surface
of the earth can expand and then contract.
If this happens often enough the expansion
and contraction of rock would eventually
cause weathering.
Plants
• Plant roots grow in cracks of rocks.
As they grow, they force open the
cracks. This is another way pieces of
rock can be broken off.
Weathering and Erosion
• Weathering and erosion often occur at the
same time. After weathering has broken
the rocks into smaller pieces, other
processes like erosion and deposition move
the broken pieces to other places.
• Weathering is a destructive force because
it changes rocks by breaking them into
smaller pieces.
Weathering processes are
divided into three
categories:
• · Physical or Mechanical Weathering
• · Chemical Weathering
• · Biological Weathering
• Physical or Mechanical
Weathering: breaks larger rocks into
smaller rocks without changing what the
rock is made of. Examples
• Chemical Weathering: involves changing
what the rock is made of. Chemical
weathering causes the rocks to become
weak and eventually crumble. Examples
• Biological Weathering: is the actual
molecular breakdown of minerals.
• Example: Lichens live on rocks and they
slowly eat away at the surface of rocks
Deposition – deltas & sand dunes
• The dunes are the product of the wind and rain
eroding nearby mountains. The dunes collect here
because the prevailing winds across the valley
blow in this direction and meet winds blowing in
the opposite direction. The sand drops to the
valley floor and begins to collect. So over the
course of millennia, the dunes have build.
Tomorrow they will be different because the wind
still blows, the sand still moves and the deposits of
sand still grow.
Western Sand Dune
Delta
• A delta is a low, watery land formed at the
mouth of a river. It is formed from the silt,
sand and small rocks that flow downstream
in the river and are deposited in the delta.
• A delta is often (but not always) shaped like
a triangle (hence its name, delta, a Greek
letter that is shaped like a triangle).
• NASA view
of a delta
from space.
Faults
• Faults are usually caused by the
Earth's crust bending and breaking in
the middle because of the forces
pressing on it. These bends and
breaks can form faults where the
earth's crust is able to move.
• Faults also mark plate boundaries.
There are three main types of faults
and each are constructive in their
own way.
Divergent Fault Line
• Divergent Fault is where two plates are moving
away from each other. (For more)
• As plates pull apart from each other the earth's
crust spreads apart. This usually causes rifts or
rift valleys. The majority of this activity takes
place deep within the oceans along plate
boundaries. As the plates pull apart hot magma is
pushed toward the surface and volcanoes occur.
This affects the Earth's surface by adding new
material to the surface.
Convergent
Fault Line
• Convergent Fault is when two plates come
together.
• Not only can this cause destruction it can
also cause construction. When two plates
collide in a collision zone the result is
mountains. The pressure of these two
plates hitting each other causes the crust
of the earth to rise. This can occur in the
oceans of the world and on land. Mountain
building is a very slow process but it is
caused by convergent faults.
Transform Fault
is when two plates
slide past each
other.
Earthquakes
• What is an
earthquake?
Earthquakes are the
shaking, rolling or
sudden shock of the
earth’s surface. They
are the Earth's
natural means of
releasing stress. More
than a million
earthquakes rattle
the world each year.
• Earthquakes most commonly occur
along faults in the crust.
Sometimes new
landforms are created.
Earthquakes can
happen on land and in
water.
An earthquake can
destroy everything
that gets into its path.
It destroys buildings,
bridges, dams, and
other structures.
Where do earthquakes happen?
Why?
Most naturally occurring earthquakes are
related to the tectonic nature of the Earth.
Such earthquakes are called tectonic
earthquakes. The Earth's lithosphere is a
patchwork of plates in slow but constant
motion caused by the release to space of the
heat in the Earth's mantle and core.
Why continued…
The heat causes the rock in
the Earth to warm so that
the plates move slowly
but surely. Plate
boundaries lock as the
plates move past each
other, creating frictional
stress. When the
frictional stress exceeds a
critical value, called local
strength, an earthquake
happens.
• The West Coast is most at risk of having an
earthquake, but earthquakes can happen in the
Midwest and along the East Coast. Earthquakes
can be felt over large areas although they
usually last less than one minute. Earthquakes
cannot be predicted - although scientists are
working on it!
Quit pushing!!
Largest Fault in the US
The San Andreas Fault
Volcanoes
• A volcano is a mountain or hill formed by
the accumulation of magma or molten rock.
Magma is typically produced at depths of
50 to 60 miles below the surface; because
liquid magma is less dense than solid rock,
it is pushed out of cracks in the Earth's
surface. Volcanic eruptions can be deadly,
damaging property and infrastructure.
Volcano Types
• Volcanoes are one of the most
powerful forces in nature. A volcano
is a hole in the earth’s crust. The
hollow holes that are in volcanoes are
called craters. There are different
types of volcanoes; shield-volcanoes,
cinder cone volcanoes, lava domes and
the most common - composite
volcanoes.
Volcanoes are basically
hollowed-out mountains with
connections to the Earth’s
magma core. There are over
500 volcanoes in the world. The
volcanoes are contained in a
circle called the Ring of Fire.
Evidence of
Steam & Magma
• Volcanoes can form on land but they
can also form in water. Volcanoes can
help build up the Earth's surface
(constructive) like the developing
Hawaiian Islands, but volcanoes can
also be very destructive to the
Earth's surface.
Destructive Volcanoes
• Volcanoes can endanger anything that
happens to be in the vicinity of an
erupting volcano such as humans,
property, and agriculture.
• Volcanoes are destructive because
when they erupt not only can they
spew hot ash and lava but they can
also cause other destructive
activities to occur.
Volcanic
Diagram
Notice the
difference in
destruction on
either side of
the volcano.
Mud flows also may occur with a volcano
eruption engulfing everything in its path..
Volcanic
Landslide step 1
• Volcanic
Landslide step 2
• Volcanoes are destructive because when
they erupt not only can they spew hot ash
and lava but they can also cause other
destructive activities to occur.
• Lava flows can destroy homes, grass, trees,
and anything else in its destructive
path. The lava which is hot melted rock
flows from one place to another burning
everything it touches.
Tsunamis and Earthquakes
• Two main destructive forces can be
triggered by a volcano: tsunamis and
earthquakes.
• Damage to the Earth's surface
caused by a volcano is often not
repairable but over many, many years
some new growth may begin to appear.
Good Thing/Bad thing
• There are many constructive
properties of volcanoes. For example,
volcanoes help the rock-cycle by
bringing rocks to the surface to form
new landforms like islands. All of the
Hawaiian Islands were created by
volcanoes. There is even a new island
forming right now.
• Another example of a volcanoes'
constructive force is that if there
are enough eruptions or a constant
lava flow a mountain can form. Some
of these mountains form on land but
many build from the bottom of
oceans.
Here are other ways a
volcano can be constructive...
• volcanic ash can be used as an
abrasive or cleaning agent
• volcanic ash can act as a mulch
• volcanoes can create geothermal
energy
• ashes can make more fertile soil
• To see an animation of an erupting
volcano click here.
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