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Unit 4 Lesson 7 Mountain Building
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Unit 4 Lesson 7 Mountain Building
Indiana Standards
• 7.2.4 Explain how convection currents in the
mantle cause lithospheric plates to move causing
fast changes like earthquakes and volcanic
eruptions, and slow changes like creation of
mountains and formation of new ocean floor.
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Unit 4 Lesson 7 Mountain Building
Stressed Out
How can tectonic plate motion cause deformation?
• The movement of
tectonic plates causes
stress on rock structures.
• Stress is the amount of
force per unit area that is
placed on an object.
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Unit 4 Lesson 7 Mountain Building
How can tectonic plate motion cause
deformation?
• When a rock is placed under stress, it deforms, or
changes shape, in a process called deformation.
• Deformation can cause rock to bend or break.
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Unit 4 Lesson 7 Mountain Building
What are two kinds of folds?
• Folding occurs when rock
layers bend under stress.
• Rock layers start out as
horizontal layers deposited
over time.
• A fold, or bend, in the rock
layers means that
deformation has happened.
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Unit 4 Lesson 7 Mountain Building
What are two kinds of folds?
• Two common types of folds are synclines and
anticlines.
• In a syncline, the youngest layers of rock are at
the core of the fold.
• In an anticline, the oldest layers of rock are at
the core of the fold.
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Anticline
Syncline
Unit 4 Lesson 7 Mountain Building
What are two kinds of folds?
• Identify the oldest and youngest layers in this
diagram.
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Unit 4 Lesson 7 Mountain Building
Faulted
What are the three kinds of faults?
• Sometimes rock is under so much stress that it
breaks.
• A crack called a fault forms when large blocks of
rock break and move past each other.
• The three main kinds of faults are strike-slip
faults, normal faults, and reverse faults.
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Unit 4 Lesson 7 Mountain Building
What are the three kinds of faults?
• Faults are classified based on how the fault blocks
move.
• The fault plane is the location where two fault
blocks meet.
• The fault block that tilts over the fault plane is
called the hanging wall.
• The fault block below the hanging wall is called
the footwall.
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Unit 4 Lesson 7 Mountain Building
What are the three kinds of faults?
• strike-slip fault, the fault
blocks move past each other
horizontally.
• Strike-slip faults form when rock
is under shear stress, or stress
that results from the sliding of
rock structures in parallel but
opposite directions.
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Unit 4 Lesson 7 Mountain Building
What are the three kinds of faults?
• normal fault, the hanging
wall moves down relative to
the footwall.
• Normal faults form when
rock is under tension, which
is stress that stretches or
pulls rock apart.
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Unit 4 Lesson 7 Mountain Building
What are the three kinds of faults?
• reverse fault, the hanging wall
moves up relative to the
footwall.
• Reverse faults form when rocks
undergo compression, which is
stress that squeezes or pushes
rock together.
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Unit 4 Lesson 7 Mountain Building
What are the three kinds of faults?
• Which kind of fault is shown in each image?
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Unit 4 Lesson 7 Mountain Building
Moving on Up
What are the three kinds of mountains?
• Mountains can form through folding, volcanism,
and faulting.
• The process by which land rises or mountains
form is called uplift.
• Because tectonic plates are always in motion,
some mountains are constantly uplifting.
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Unit 4 Lesson 7 Mountain Building
What are the three kinds of mountains?
• Folded mountains form when rock layers are
squeezed together and pushed upward.
• Most folded mountains form at convergent
boundaries.
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Unit 4 Lesson 7 Mountain Building
What are the three kinds of mountains?
• Volcanic mountains form when melted rock erupts
onto Earth’s surface.
• Most volcanic mountains form at convergent
boundaries.
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Unit 4 Lesson 7 Mountain Building
What are the three kinds of mountains?
• Fault-block mountains form when tension makes
the lithosphere break into many normal faults.
• Pieces of the lithosphere sink, and the blocks left
standing are the mountains.
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