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What to do…
•Answer these 2 questions in your journal!
•1. Tectonic plates consist of…
a. continental crust.
b. oceanic crust.
c. both continental and oceanic crust.
d. mesosphere.
•2. The deep interior of the Earth can be mapped using
a. seismic waves.
b. sonar.
c. information from drilling expeditions.
d. ocean waves.
Deforming the
Earth’s Crust
Standards:
Chapter 15, Section 4
7.5 – Recognize that lithospheric plates on the scale
of continents and oceans continually move at rates
of centimeters per year
7.6 – Describe the relationship between plate
movements and earthquakes, mountain building,
volcanoes, and sea floor spreading
Deformation
•Stress is the amount of force
per unit area on a given
material
•The process by which the shape
of a rock changes because of
stress is called deformation
• Two types of deformation can occur to
rocks under stress
• Layers can bend when stress is applied
to them
• When too much stress is applied, they
can reach their elastic limit and break
Compression & Tension
• Compression is the type of stress
that occurs when an object is
squeezed
• Tension is stress that occurs when
forces act to stretch an object
Folding
•Folding is the bending of rock
layers because of stress in the
Earth’s crust
•By assuming all rock starts in
horizontal layers, scientists know
deformation has occurred when
they see a fold.
Types of Folds
• Anticlines, upward, arching fold
• Synclines, downward, trough-like
folds
• Monoclines, horizontal
Anticline
Syncline
Faulting
• Some rock layers break when too
much stress is applied to them.
• The surface along which a rock
breaks and slide past each other is
called a fault
• The two sides of a fault are known as the
hanging wall and the footwall
• The type of fault that forms is dependent
on where the hanging and footwall are
located
Types of Faulting
•There are three types of
faults that occur
•Normal Faults
•Reverse Faults
•Strike-Slip Faults
Normal Faults
•When rocks are pulled apart
because of tension, normal
faults often form
•When a normal fault moves, it
causes the hanging wall to
move down relative to the
footwall
Reverse Fault
• When rocks are pushed together by
compression, reverse faults often form
• When a reverse fault moves, it causes the
hanging wall to move up relative to the
footwall
Compression
forces
Compression
forces
Strike-Slip Fault
•Forms when opposing forces
cause rock to break and move
horizontally
Plate Tectonics & Mountain Building
• When tectonic plates collide, land
features that start as folds and
faults, can eventually become
large mountain ranges
Folded Mountains
• Form when rock layers are squeezed
together and pushed upward
• These mountains form at convergent
plate boundaries
• Appalachian Mountains 390 million years
ago
Fault-Block Mountains
• Fault-Block mountains form when
tension causes large blocks of the
Earth’s crust to drop down relative
to other blocks
• Often leaves sharp, jagged peaks
Volcanic Mountains
• Located at convergent plate
boundaries where oceanic crust sinks
into the asthenosphere at subduction
zones
• The rock that is melted at subduction
zones forms magma which rises to the
surface and erupts
• Sometimes these mountains can rise
above the sea and become islands
• A majority of the tectonically active
volcanic mountains have formed
around the Pacific Plate which is
known as the Ring of Fire
Uplift and Subsidence
•Uplift is the rising of regions of
Earth’s crust to higher elevations
•Subsidence is known as the
sinking of Earth’s crust to lower
regions
Uplifting of Depressed Rock
• One way areas rise without deforming is
a process known as rebound
• Rebound occurs when the crust slowly
springs back to its previous elevation
• Rebound happens when a weight is
removed from a region ( glacial
melting)
Tectonic Letdown
• Subsidence can occur when the
lithosphere becomes stretched
• A rift zone is a set of deep cracks that
forms at a divergent plate boundary
• As the plates move apart, the rift zone
begins to subside between the plates
Put it together…
•Complete your study guide!
•It is due tomorrow!