Source: Panorama of Landforms, NASA

Lesson Title: / Tectonic Forces
World Geography, Module 1, Lesson 6
Summary:
RC/TEKS: / 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).
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 soil-building 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.

This is an image of common land forms Listed counterclockwise are a volcano flood plain butte mesa plateau strait cape island archipelago sound peninsula isthmus harbor ocean river mouth delta barrier sand bar plain gulf beach tributary river valley waterfall river source moraine mountain glacier divide river hills canyon alluvial fan basin and lake

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:

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):

Match the earth's events to the corresponding time period.

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.

Image of a map of Iceland and an illustration of the Mid Atlantic Ridge that runs through it There are arrows depicting the left half of the map as the North American Plate and the right half of the map as the Eurasian Plate The arrows indicate movement in opposite directions

Source: Map of Mid-Atlantic Range splitting Iceland and separating North American Plate and Eurasian Plate, U.S. Geological Survey / 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.

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.

This is an image of hot lava splashing against volcanic rock Source: Lava fountains spouting from eruptive fissures during the October 1980 eruption of Krafla Volcano, Gudmundur E. Sigvaldason, U.S. Geological Survey

Take a look at this news report about a volcano that erupted in Iceland in April of 2010. Click on the following link.

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.

Image of the map of the Ring of Fire
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. / Image of the oceanic continental convergence model that is the conveyor belt meeting and the oceanic crust on the left side is sinking On the surface there is a volcanic arc above the continental crust on the right side of the image There is a depiction of volcanic eruption in this area

Image of the oceanic continental convergence model that is the conveyor belt meeting and the oceanic crust on the left side is sinking On the surface there is a volcanic arc above the continental crust on the right side of the image There is a depiction of volcanic eruption in this area

Source: Oceanic-Continental Convergence, U.S. Geological Survey
Image of the snow capped Andes Mountains

Source: The Convergence of the Nazca and South American Plates, George Erickson, U.S. Geological Survey / Convergent Boundaries:
Real World Example
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.

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: Andreas Fault

Watch the following video clips of various earthquakes from California:

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.

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.

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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.