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Lesson 1: Interaction at Plate Boundaries
Lesson 2: California Geology
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5.1 Interactions at Plate Boundaries
fracture
rift valley
fault
convergent plate
boundary
divergent plate
boundary
continental rifting
subduction
transform plate
boundary
5.1 Interactions at Plate Boundaries
Stress and Deformation
• Earth’s lithosphere is made up of crust and
upper mantle that are broken into plates.
• Each plate travels at different speeds and in
different directions.
• Collisions between plates causes stress at
plate boundaries, resulting in deformation.
5.1 Interactions at Plate Boundaries
Stress and Deformation (cont.)
5.1 Interactions at Plate Boundaries
Deforming Rocks
• Plastic deformation occurs when rocks
change shape by folding under high
temperatures and pressure.
• Elastic deformation occurs when rocks
resume their original shapes after the
stress is removed.
5.1 Interactions at Plate Boundaries
Deforming Rocks (cont.)
• A fracture is a break or crack in rock.
• If rock on side of a fracture has moved
relative to the other side it is called a fault.
5.1 Interactions at Plate Boundaries
Types of Stress
• Three main types of stress:
– Tension: rocks are stretched
– Compression: rocks are squeezed
– Shear: rocks slide horizontal in
opposite directions
5.1 Interactions at Plate Boundaries
Types of Stress (cont.)
5.1 Interactions at Plate Boundaries
Types of Faults
• Three main types of faults:
– Normal faults
– Reverse faults
– Strike-slip faults
5.1 Interactions at Plate Boundaries
Normal Faults
• Normal faults result from tension stress
and slope at an angle.
5.1 Interactions at Plate Boundaries
Reverse Faults
• Reverse faults result from compression
stress and slope at an angle.
5.1 Interactions at Plate Boundaries
Strike-Slip Faults
• Strike-slip faults result from shearing stress
and are often vertical.
5.1 Interactions at Plate Boundaries
Types of Plate Boundaries
• Divergent plate boundary occurs when
two lithospheric plates move apart.
• Convergent plate boundaries form
when two lithospheric plates move toward
each other.
5.1 Interactions at Plate Boundaries
Divergent Plate Boundaries
• Mid-ocean ridges occur along divergent
plate boundaries.
5.1 Interactions at Plate Boundaries
Divergent Plate Boundaries (cont.)
• Continental rifting occurs when two
continental plates are being pulled apart.
– East African Rift
– Gulf of California
5.1 Interactions at Plate Boundaries
Convergent Plate Boundaries
• Three possible interactions:
– Ocean-to-ocean: two oceanic plates move
towards each other—subduction occurs
as one plate is forced down into the
mantle beneath another plate
– Ocean-to-continent: oceanic plate
subducts beneath continental plate
– Continent-to-continent: compression
stresses force crust to rise up, thicken,
and shorten
5.1 Interactions at Plate Boundaries
Convergent Plate Boundaries (cont.)
5.1 Interactions at Plate Boundaries
Transform Plate Boundaries
• A transform plate boundary exists when
two plates slide horizontally past one another.
5.1 Interactions at Plate Boundaries
Transform Plate Boundaries (cont.)
• Oceanic transform plate boundaries
connect pieces of the mid-ocean ridges.
• Transform plate boundaries can slice
through continental lithosphere as strikeslip faults.
• Large earthquakes can occur on these
faults and can be very destructive.
Where do most
earthquake epicenters
and volcanoes occur?
5.1 Interactions at Plate Boundaries
What type of deformation results
from tension?
A thickening of the
lithosphere
B compression of the
lithosphere
C thinning of the
lithosphere
0%
0%
D
0%
C
D movement of rocks
past each other
0%
B
A
B
C
D
A
1.
2.
3.
4.
5.1 Interactions at Plate Boundaries
Subduction results from _____.
A one oceanic plate being
forced into the mantle
beneath another plate
B two plates moving away
from each other
C two continental plates
colliding with each other
0%
0%
0%
D
0%
C
D two continental plates
sliding horizontally past
each other
B
A
B
C
D
A
1.
2.
3.
4.
5.1 Interactions at Plate Boundaries
What type of plate boundary
separates the North American
and Pacific Plates in California?
A convergent
B rift
C transform
D divergent
0%
0%
D
0%
C
0%
B
A
B
C
D
A
1.
2.
3.
4.
5.2 California Geology
San Andreas Fault
5.2 California Geology
Plate Tectonics in California
• A continental transform plate boundary
cuts across California.
• A convergent plate boundary resides off
the northern shore of California.
• This active plate tectonic setting produces
earthquakes, volcanoes, and mountains.
5.2 California Geology
80 Million Years Ago
5.2 California Geology
Transform Plate Boundary
• The San Andreas
Fault is a transform
plate boundary
between the North
American and
Pacific Plates.
• This boundary
switches to an
oceanic transform
boundary when it
goes out to sea.
5.2 California Geology
Convergent Plate Boundaries
• Two small oceanic
plates are being
subducted in the
Cascadia Subduction
Zone.
• This subduction
zone forms a
convergent plate
boundary.
5.2 California Geology
California’s Mountains
• California’s
mountains often
formed from
interactions at
several plate
boundaries.
5.2 California Geology
Subduction
• The Klamath Mountains, Costal Ranges,
peninsulas, and Sierra Nevada all contain
igneous and metamorphic rocks formed
below the surface.
• These rocks were formed when an ancient
oceanic plate subducted beneath the North
American Plate.
5.2 California Geology
Rifting
• Some mountains in California have formed
from tension stress.
• The Panamint Range is rising up as the crust
in eastern California stretches.
5.2 California Geology
Convergent plate boundaries in
California are important in _____.
A the development of
California’s rift valleys
B the formation of
California’s mountains
C movement along the
San Andreas Fault
0%
0%
D
0%
C
D the existence of the
Gulf of California
0%
B
A
B
C
D
A
1.
2.
3.
4.
5.2 California Geology
The San Andreas Fault is a
transform plate boundary; this
also makes it a _____.
A subduction zone
B convergent plate
boundary
C rift valley
0%
0%
0%
D
0%
C
D strike-slip fault
B
A
B
C
D
A
1.
2.
3.
4.
5.2 California Geology
Which of the following are active
California volcanoes?
A Lassen Peak and
San Andreas
B Sierra Nevada and
Mount Shasta
C Lassen Peak and
Mount Shasta
0%
0%
D
0%
C
D Panamint Range and
Mount Shasta
0%
B
A
B
C
D
A
1.
2.
3.
4.
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What does shearing stress produce
when plates slide past each other?
A subduction zones
B strike-slip faults
C divergent plate
boundaries
D rift valleys
0%
0%
D
0%
C
0%
B
A
B
C
D
A
1.
2.
3.
4.
Where do mid-ocean ridges
usually occur?
A convergent plate
boundaries
B strike-slip faults
C divergent plate
boundaries
0%
0%
0%
D
0%
C
D normal faults
B
A
B
C
D
A
1.
2.
3.
4.
In what areas of the Earth does present-day
continental rifting occur?
A eastern Africa and
western South America
B the Gulf of California and
eastern South America
C Gulf of California and the
Himalayas
0%
0%
0%
D
0%
C
D eastern Africa and the
Gulf of California
B
A
B
C
D
A
1.
2.
3.
4.
Which two oceanic plates are being
subducted in the Cascadia Subduction
Zone?
A San Andreas and
Juan de Fuca
B Juan de Fuca and Gorda
C Gorda and San Andreas
D San Andreas and Pacific
0%
0%
D
0%
C
0%
B
A
B
C
D
A
1.
2.
3.
4.
The San Andreas Fault is a(n) _____.
A strike-slip fault
B oceanic transform
plate boundary
C subduction zone
D rift valley
0%
0%
D
0%
C
0%
B
A
B
C
D
A
1.
2.
3.
4.
SCI 1.f
Northern California is located _____.
A above a subduction
zone
B below a subduction
zone
C above a rift valley
D below a rift valley
0%
0%
D
0%
C
0%
B
A
B
C
D
A
1.
2.
3.
4.
SCI 1.e
Which of the following scenarios would
most likely result in the development of
mountains?
A two oceanic plates
pulling apart
B two continental plates
colliding
C one oceanic and one
continental plate colliding
0%
0%
0%
D
0%
C
D erosion by wind and water
B
A
B
C
D
A
1.
2.
3.
4.
SCI 7.g
The Pacific Plate moves about
3.4 cm/year relative to the ____.
A Atlantic Plate
B San Andreas Plate
C North American Plate
D Gorda Plate
0%
0%
D
0%
C
0%
B
A
B
C
D
A
1.
2.
3.
4.
SCI 1.e
What is subduction?
A the process in which one
plate is forced down into
the mantle beneath the
other plate
B the result of two plates
moving away each other
C the process of two
continental plates colliding
0%
0%
0%
D
0%
C
D the result of two plates
sliding sideways past
each other
B
A
B
C
D
A
1.
2.
3.
4.
SCI 1.e
Deformation that results from
compression stress is _____.
A the thickening of the
lithosphere
B the melting of
the rocks
C the thinning of the
lithosphere
0%
0%
D
D always minimal
0%
C
0%
B
A
B
C
D
A
1.
2.
3.
4.
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Interactive Table