Download Lesson Title: Tectonic Forces World Geography, Module 1, Lesson 6

Lesson Tectonic
Title: Forces
World Geography, Module 1, Lesson 6
Summary: World Geography, Module 1, Lesson 6 - Given the types of tectonic forces, identify examples of landforms that
have been built up by different tectonic forces (plate collision, volcanic activity, folding, faulting, lateral plate
movement).
RC/TEKS: Reporting Category 2, TEKS 3.B - Physical processes shape patterns in the physical environment. SWBAT describe
the physical process that affect the environments of regions, including weather, tectonic forces, erosion, and soilbuilding processes.
A Short Review: Landforms & Physical Processes
A Short Review: Landforms & Physical Processes
tectonic forces
forces that originate beneath the surface that alter the surface configuration of the earth as a result of plate movement
Before you learn about tectonic forces and their impact on earth, let's review some important information. First, we need to
understand landforms. Landforms are the various features on the surface of the earth such as plains and plateaus; hills and
valleys; and mountains and volcanoes. Review the image below to see more landforms.
Source: Panorama of Landforms, NASA
In this lesson, you will also study the factors that change these landforms called physical processes. Some landforms are
created by the action of wind, water, and ice. These physical processes change the Earth's surface by carving and eroding
land surfaces, carrying and depositing soil, sand, and other debris. Crustal movement and other tectonic activity inside Earth
create landforms, such as mountains, faults, sinks, and volcanoes.
VOCABULARY YOU SHOULD KNOW:
tectonic forces
forces that originate beneath the surface that alter the surface configuration of the earth as a result of plate movement
landforms
physical features on the Earth’s surface including plains, plateaus, mountains, hills, and valleys. Each is distinctive for its
shape, form, and the process by which it was formed.
physical processes
natural forces that create and wear down the earth’s surface
What are Tectonic Forces?
Geographers, geologists, and many other scientists study the movement of the plates and the changes they cause in order
to understand how the earth is continually being reshaped. You will study various types of tectonic forces. (Helpful Hint:
This movement of the plates is sometimes called the continental drift.)
The internal forces that shape the earth's surface begin beneath the lithosphere. Rock in the asthenosphere is hot enough to
flow slowly. Heated rock rises, moves up toward the lithosphere, cools, and circulates downward. Rising above this
circulation system are the tectonic plates, large moving pieces of the earth's lithosphere. Look carefully at the image below
and click on lithosphere and asthenosphere.
Activity:
Watch this video to get an understanding of plate tectonics and tectonic forces:
http://www.youtube.com/watch?v=QDqskltCixA
Source: The Early Earth and Plate Tectonics, Michaelfreudiger, YouTube
After watching the video answer the following questions (feel free to watch the video again if you missed something):
1. Match the earth's events to the corresponding time period.
2. Can you explain how the two causes of heat below the earth's surface (convection flow and radioactive heat) affect
the movement of plates above the earth's surface?
Types of Tectonic Forces: Divergent Boundaries & Convergent Boundaries
(Divergent Boundaries)
Imagine that you are a geographer studying what is below the earth's surface; picture two giant conveyor belts, facing each
other but slowly moving in opposite directions. Click on the link below to see divergent boundaries at work.
Divergent Boundaries
This is an example of divergent boundaries which occur along spreading centers where plates are moving apart and new
crust is created by magma pushing up from the mantle. Click the Divergent Boundaries button to see why they are
important for us to study.
The volcanic country of Iceland,
which straddles the Mid-Atlantic
Ridge, offers scientists a natural
laboratory for studying on land the
processes also occurring along the
submerged parts of a spreading
ridge. Iceland is splitting along the
spreading center between the North
American and Eurasian Plates.
Source: Map of Mid-Atlantic Range splitting Iceland and separating North
American Plate and Eurasian Plate, U.S. Geological Survey
Activity – Think about the following:
The Mid-Atlantic Ridge moves about 2.5 centimeters per year- this equals 25 kilometers in 1million years! If you were a
geographer (or another type of scientist) studying this information:

What changes to the Atlantic Ocean sea floor would you predict?

What changes to the continents surrounding the Mid-Atlantic Range would you predict?
(Convergent Boundaries)
You will now study another type of tectonic force called convergent boundaries. This type of tectonic force occurs where
crust is destroyed as one plate dives under another. Depending upon where this plate collision takes place, convergence
boundaries form what we know as mountain ranges, volcanic activity, and even earthquakes.
Source: Lava fountains spouting from eruptive fissures during the
October 1980 eruption of Krafla Volcano, Gudmundur E. Sigvaldason, U.S. Geological Survey
following link.
Take a look at this news report about a volcano that erupted in Iceland in April of 2010. Click on the
http://www.youtube.com/watch?feature=player_embedded&v=FhrNragcPL4
Source: Iceland volcano eruption continues, more test flights through ash planned, Russia Today, YouTube
Activity – Think about the following:

List 3 things that you observed in the video clip about the volcano eruption.

Based on the video, what danger does volcanic activity pose to people?
To learn more about volcanoes, read below and study the map:
The "Ring of Fire" is an arc stretching from New Zealand, along the eastern edge of Asia, north across the Aleutian Islands of
Alaska, and south along the coast of North and South America. The Ring of Fire is composed of over 75% of the world's
active and dormant volcanoes.
This huge ring of volcanic and seismic (earthquake) activity was noticed and described before the invention of the theory of
plate tectonics. We now know that the Ring of Fire is located at the borders of the Pacific Plate and other major tectonic
plates.
Close
Convergence: Subduction
Earth's size has not changed much during the past 600 million
years. Scientists believe this is due to the crust being destroyed
at the same rate that it is being created (remember the
conveyor belt).
Such destruction (recycling) of crust takes place along
convergent boundaries where plates are moving toward each
other, and sometimes one plate sinks (subduction) under
another. The location where the sinking of a plate occurs is
called a subduction zone. As the bottom plate starts to melt,
magma rises and forms volcanoes at the surface.
Source: Oceanic-Continental Convergence, U.S. Geological Survey
Convergent Boundaries:
Real World Example
Source: The Convergence of the Nazca and South American Plates, George
Erickson, U.S. Geological Survey
Off the coast of South America along the Peru-Chile
trench, the oceanic Nazca Plate is pushing into and being
subducted under the continental part of the South
American Plate. In turn, the overriding South American
Plate is being lifted up, creating the towering Andes
Mountains (as pictured here), and surrounding ridges, the
backbone of the continent. Strong, destructive
earthquakes and the rapid uplift of mountain ranges and
ridges are common in this region.
Convergent Collision:
When two continental plates collide, neither one is subducted;
also the plates buckle and fold. Sometimes a double thickness
of crust results in the formation of mountain ridges. The image
to the right is a continental-continental convergence. Look at
the example of the continental-continental convergence model
here.
Source: Continental-Continental Convergence, U.S. Geographical
Survey
Convergence: Collision - A Real World Example
This photo is a sunset view of towering, snow-capped Mt.
Everest, a famous peak in the Himalayan Mountain Range in
Nepal. The Himalayas, the highest mountains on earth, are an
example of convergence collision. The Himalayas rise 1cm per
year- that is growth rate of 10km in a million years. Look at the
photo below to get an idea of how tectonic forces work over
time.
Source: Mt. Everest, from the village of Lobuche (Solu-khumbu),
Nepal, Gimmy Park Li, U.S. Geological Survey
Source: India. Giant talus in the Himalaya foothills near Dehra dun, Sahasradhara, 1964, McKee, U.S. Geological Survey
Source: The Himalayan Mountains, NASA
This is a satellite map of Asia, provided by NASA, where the Himalayas are clearly shown.
Types of Tectonic Forces: Transform Boundaries (Folding and Faults)
Another type of tectonic force is Transform Boundaries. This is the zone between two plates sliding horizontally past each
other. When two plates meet each other, they can cause folding and cracking of the rock. The transformation of the crust by
folding or cracking occurs very slowly, often only a few centimeters or inches in a year. This occurrence causes what is
commonly known as faults and they often produce earthquakes. Transform boundaries usually happen on the ocean floor,
however, a few occur on land, for example the San Andreas Fault zone in California.
Take a look at the map in this section and identify the San Andreas Fault.
Transform Boundaries: Faults
The San Andreas Fault
This image (right) is an aerial view of the San
Andreas Fault. This part of the fault slices
through the city of San Luis Obispo in California.
The graphic below shows how the San Andreas
Fault Zone causes a shift between the Pacific
Tectonic Plate and the North American Tectonic
Plate. Movement in the San Andreas Fault Zone
sometimes cause earthquakes in the area.
Source: San _Andreas, Robert E. Wallace, U.S. geological Survey
Watch this video to learn more about the San Andreas Fault and its impact.
When you get to the AISD Show and Share by clicking the following link, you need
to Sign In at the top right with your AISD username and password.
http://escdmssns.amaisd.org/p.jsp?i=495
Source: San Andreas Fault (Discovery Channel)
Source: San Andreas Fault Zone, U.S. Geological Survey
Source: City of Los Angeles, U.S. Geological Survey
Click on the link below to take a look at the San Andreas Fault line from above:
Watch the following video clips of various earthquakes from California:
http://gallery.usgs.gov/videos/184
http://youtu.be/ONpBmjoAjUM
http://youtu.be/hhe4oM5vjfE
Andreas Fault
Activity:
Imagine that you live in Los Angeles, California, you have learned that a good friend is planning to move to the area, your
friend has some concerns (your friend saw the video clips!) about the impact of the San Andreas Fault being so close. Write
your friend a quick email that includes the following:

A brief description of the San Andreas Fault.

Briefly describe how the fault impacts Los Angeles and other areas in California.

Your opinion about whether or not he should live in the area.
Other Physical Processes: Erosion
Another physical process is called erosion. Erosion in all of its forms reshapes landforms and coastal regions, as well as
riverbeds and riverbanks. Erosion occurs when weathered material is moved by the action of wind, water, ice, or even
gravity. For erosion to take place, a transporting agent (such as water) must be present.
Erosion involves material moving from one location to another resulting in the lowering of some locations and increasing in
elevation in others. For example, water might carry topsoil from a hill into a river and gradually cause the river to become
narrower. Glaciers, waves, stream flow, or blowing winds cause erosion by grinding rock into smaller pieces.
Activity:
Analyze the following examples of erosion and try to determine the causes of the each one:
Watch the following video that shows coastal erosion in a 4-week time lapse at Drew Point, Alaska.
http://youtu.be/LaB3nKxPjiU
Source: Drew Point, Alaska Time-Lapse Photograph of Coastal Erosion, USGS, YouTube
1. The cause(s) of the coastal erosion in the video is (are):
A. Water
B. Wind
C. Ice
D. Gravity
E. All of the above
FEEDBACK: E. All of Above - Because it sits on the coast, water is the most important factor in erosion. Wind is a major
factor. Since the video is taken in Alaska, it is safe to assume that ice has some degree of influence on the erosion in this
area. Gravity is a factor in this erosion; notice how the land began to sink and fall over a few weeks.
Source: Bank Erosion, U.S. Geological Survey
This is a photo of an active bank erosion on the right bank of the Missouri River, located southwest of Brockton, Montana.
2. The cause (s) of this river bank erosion in Montana, most likely is (are):
A. Water
B. Wind
C. Ice
D. Gravity
E. All of the above
FEEDBACK: E All of Above - This is the bank of a major river so water is a very important factor in erosion. Wind plays a
major role in the erosion; can you see the ripples in the water? Montana does get a lot of snow and ice which would make
ice a factor in erosion. The rocks that are seen crumbling are being pulled by gravity along with the other factors.

Source: Rapid Erosion, Shad O 'Neel, U.S. Geological Survey
This is a photo of the St. Elias Mountain Range in Icy Bay, Alaska. This area is known for having some of the fastest erosion
rates on Earth.
3. Based on this photo, what factors do you think caused this area to have the fastest erosion rates on Earth?
A. Water
B. Wind
C. Ice
D. Gravity
E. All of the above
FEEDBACK: E All of Above – Melted ice and snow is flowing from top of mountain into waterfall; with the
mountains being so elevated, wind is a constant factor in the erosion here; there is evidence of ice and snow above
and below the mountain; it appears that gravity may be a factor in the rocks that have fallen just below the cliffs.
4. Erosion occurs when weathered material is moved by wind, water, ice, or gravity.
A. True
B. False
FEEDBACK: A True – For erosion to occur, a transporting agent, such as water must be present.
If answered false: Incorrect: something has to move or transplant the debris, right?
Other Physical Processes: Soil Building
The final physical process that you will examine is glaciation. Glaciation is the modification of the land surface by the action
of glaciers (large blocks of ice). Since glaciers move, they can pick up and transport rocks, just as in the physical process of
erosion. Glaciers transport material and can melt, which means that they can also deposit material. Glaciated landscapes are
the result of both glacial erosion and glacial deposits.
Source: Global Warming, Frederico Stevanin, FreeDigitalPhotos.net
Source: Submarine Surfacing, Shad O 'Neel, U.S. Geological Survey
This is an image of several miles of glaciers that have surfaced from underwater. These glaciers are a part of the Yahtse
Glacier in Alaska.
The glaciers in this photo most likely are caused by which of the following factors?
A. Water
B. Wind
C. Ice
D. All of the above
FEEDBACK: D - These glaciers were actually submarine (underwater) glaciers that surfaced. Wind is usually
present in glaciations and causes the glaciers to move. Ice is a major factor in glaciations.
Source: Ice Wonderland, Florian Maldonado, U.S. Geological Survey
This is a photo of several small glaciers on Vitus Lake, Bering Glacier, Alaska.
The glaciers in this photo most likely are caused by which of the following factors?
A. Water
B. Wind
C. Ice
D. All of the above
FEEDBACK: D – These glaciers sit on a lake so water is a major factor in glaciations here. Judging from the ripples
on the lake, the wind has an impact on glaciers moving in this area. Wind is most likely the cause of the glaciers
breaking apart. Ice is a major factor in glaciations; ice is the material that makes up the glaciers.