Download left click to view and right click to download.

LESSON FOUR - Building Mountains
ANSWER KEY
Lesson Four: Building Mountains
Vocabulary Station
Part A: Describe what is meant by each of the following terms. You may write in jot note
form.
Deformation
Compression
- breaking, tilting and folding of rocks
- “de” means undo
- “form” means shape
- type of stress on rocks that squeezes
rocks together
- makes rocks denser and smaller in
volume
Tension
Shearing
- type of stress that pulls on rocks
causing them to stretch over a larger
area; rock becomes thinner in the
middle
- type of stress on rocks that pushes
rocks in 2 opposite directions causing
rocks to twist or bend apart
- may also see rocks slide past each
other
Fold
Rift Valley
- any bend in a rock; either upward or
downward
- valley created when block of land
between two normal faults slides
down
Plateau
Syncline
- raised area created when block of
land between two faults is thrust
upward
- a downward fold in a rock
Anticline
- an upward fold in a rock
Lesson Four: Building Mountains
Discussion Question Station
Answer the following questions in sentence form.
1. Temperature is one of the four factors determining whether or not a rock is likely to fault
(break) or fold. Increased temperature usually results in rocks folding. Lower
temperatures usually result in a fault or break in the rocks.
The other two factors listed below also determine whether or not rocks will fault
(break) or fold. Tell the effects of the various factors on rocks.
TYPE OF ROCK - brittle versus ductile
Brittle rock is more likely to fault (break); ductile will fold (bend)
HOW STRESS IS APPLIED - quick application of pressure versus slowly applied
pressure
Pressure applied quickly will cause a rock to fault; applied slowly, a rock
will fold.
2. List four ways that mountains can be created.
Folding, faulting, dome building, volcanic activity, colliding continents
3. What is the difference between an underwater trench and an underwater ridge?
Underwater trench is a deep underwater valley that is formed when oceanic
and continental crust collide at a subduction zone. These are located at
converging boundaries.
An underwater ridge is found in the centre of underwater mountain chain
(also known as a ridge). This ridge is created at a divergent boundary.
4. Draw the following types of mountain formations:
Folded Mountains
Dome Mountains
Fault Block Mountains
Reverse Fault Mountains
Lesson Four: Building Mountains
Hands-On Station
The purpose of this activity station is to show how mountains can form by folding.
Materials:
5 rectangular strips of modelling clay, each a different color and the same size
Procedure:
1. Place one piece of clay on your desk. Lay the other pieces one by one on top of
each other to form a pile.
2. Place your hands at either end of the clay with the palms facing inward.
3. Slowly, move your hands together, applying pressure to each side of the clay.
4. Stop when your hands are about 10 centimeters apart.
5. Draw a diagram of your clay below.
Questions:
1. What do your hands represent in this activity?
Pressure (tension)
2. What does the modelling clay represent in this model?
Rock (ductile)
3. What happens to the clay as you move your hands together?
Begins to fold upward and downward
4. Why doesn’t the clay break as it is squeezed together?
It is ductile or bendable because it is soft.
5. Write a summary statement that answers the question: “How do mountains fold?”
Include a diagram with your answer.
Answers will vary. Students should include information about pressure
being applied slowly will more likely cause a rock to bend. Whether or not the
rock is ductile will also have an effect on folding.
Lesson Four: Building Mountains
Computer Station
CLICK ON Continental Slide
http://cgi.pbs.org/wgbh/aso/tryit/tectonics/convergent.html
1. If the Earth’s crust separates at divergent boundaries and creates new crust, why
doesn’t the Earth “grow” in size?
The answer is subduction. In locations around the world, ocean crust subducts,
or slides under continental crusts and turns back into molten rock.
2. At approximately what depth (in kilometers) does the rock of the oceanic plate begin to
turn to molten rock?
At a depth between 300 and 700 kilometers, the rock of the descending plate
melts.
CLICK ON Continental Crush
http://cgi.pbs.org/wgbh/aso/tryit/tectonics/crush.html
1. Why does the oceanic crust slide beneath the continental crust at a subduction zone?
This is because the land mass is more buoyant, or lighter, than the ocean
floor.
2. What happens when two land masses meet?
The two crush together at what is known as a collisional boundary. They crumple
and fold. Some pieces of land are thrust over or under other pieces. The result is a
mountain range.
3. The Himalayas and the Appalachian Mountains were both formed by colliding
continental plates. How do scientists know that the Appalachians were formed before the
Himalayas?
All that remains of the Appalachians are eroded tops. The Himalayas are still high
and jagged, comparatively not as affected by erosion.
CLICK ON Sea-Floor Spread
http://cgi.pbs.org/wgbh/aso/tryit/tectonics/divergent.html
1. New ocean floor is created at what part of an underwater mountain chain?
It is called a ridge.
2. Sea floor spreading
is the name scientists give to the formation of new crust on
the ocean floor.
CLICK ON Slippin’ and Slidin’
http://cgi.pbs.org/wgbh/aso/tryit/tectonics/transform.html
1. Describe how an earthquake occurs at a transform boundary.
Two plates move against each other, building up tension, releasing the tension in
a sudden and often violent jerk. This sudden jerk creates an earthquake.