Earthquakes, Volcanoes & Plate Tectonics
Name: _____________________________ Date: ______ Period: _____
I. Plate Tectonics (pg 494-495)
Fig 1
A. What is the theory of plate tectonics?
B. Look at the image to the right, what does figure 1 show you about the Earth?
C. Who was Alfred Wegener and what was his hypothesis?
D. What is continental drift?
E. Evidence for continental drift:
a. ________________________ fit of the continents (South America and Africa seem to fit like a puzzle).
b. Similar _____________________have been found on different continents.
c. Remains of warm-weather plants in ________________________ areas and glacial deposits in
_____________________ areas suggests that continents have moved.
d. Wegener also matched up ______________________________________ ranges that had the same rock types,
structures, and ages, but that are now on opposite sides of the Atlantic Ocean. He concluded that
they formed as a single mountain range that was separated as the continents drifted.
F. All continents were once connected as one large landmass called __________________________________________.
The landmass broke apart, and the continents drifted to their present positions.
G. What was the problem with Alfred Wegener’s hypothesis?
II. Sea-floor Spreading (pg 496-498)
A. Using sonar, scientists mapped the sea-floor & discovered mid-ocean ridges. What is a mid-ocean ridge?
B. Where is the mid-ocean ridge found? In one
ocean or in all of Earth’s oceans?
C. Look at the image to the right. Put an X where
you would find the oldest crust and a Y where
you would find the youngest crust.
D. Who came up with the theory of sea-floor
spreading?
E.
What is the theory of sea-floor spreading?
Continent
Continent
Mid-ocean
Ridge
F. In the 1960’s Harry Hess suggested the theory of Sea-floor spreading. Fill in the missing terms below.
a. Hot, ________________ dense magma,
below the Earth’s lithosphere rises
upward to the surface at a
___________________________ ridge.
b. The magma moves upward and
flows from the cracks, cools and
forms new ____________________ crust.
c. The formation of new crust
___________________ the plates apart
G. Sea-floor spreading is adding new sea-floor to the bottom of the ocean, but the Earth is NOT getting
bigger and bigger. How can this be so?
H. What is subduction?
I.
Why does subduction occur?
J.
On the image label the continental crust,
oceanic crust, and subducting plate.
K. What is a trench?
L. What is the relationship between sea-floor spreading and subduction?
M. The ocean floor is not very old. In fact the ocean floor is renewed every _______________ million years.
N. Explain how the magnetic stripes found on the sea-floor support the theory of sea-floor spreading.
III. Force Strong Enough to move Continents (Pg 497-498)
A. How do convection current move Earth’s plates?
B. Where does the heat come from that drives convection currents?
C. Where is the temperature of the mantle material greater, at
point A or point B? Explain
B
D. Where is the density of the material greater, at point B or
point C? Explain.
C
A
IV. Plate Boundaries (pg 499--501 )
A. What is the law of superposition?
B. What is the law of original horizontality?
C. How fast do plates move?
D. Fill in the appropriate data on the 3 types of plate boundaries below.
Type of
How Plate Moves
Picture
Boundary
Divergent
Boundary
Convergent
Boundary
Transform
Boundary
Examples



Mid-ocean ridge
African rift valley
Iceland


Subduction zones
Himalayas


San Andreas Fault
Andes
V. Earthquakes, Folds & Faults (pg 502-503)
A. What is an earthquake?
B. What is a seismic wave?
C. Earthquakes happen because of the ways that plate movements affect the lithosphere. The forces of
plate movements cause deformation. What is deformation and what is stress?
D. As tectonic plates move, they cause stress in the crust, which in turn causes
faults and folds. Explain these terms in more detail.
a. Faults:
b. Folds:
E. Fill in the table:
Type of Fault
What force creates
fault? (compression,
tension, or shearing)
Does the ground move
vertically (up & down)
or horizontally?
Strike-slip
What type of plate
boundary? (divergent,
convergent, transform)
Types of
Earthquakes
Shallow
Normal
Shallow and
intermediate
Reverse
All types
VI. Seismic waves
A. Earthquakes occur because __________________________ have exceeded the __________________________ of the rock.
B. Use figure 35 pg 504 to label the parts of an earthquake.
C. Compare and contrast P and S waves?
D. Which waves produce the most damage?
E. What is a seismograph?
F. The circles represent seismic waves received from a seismograph station, where would the epicenter of
the earthquake be? Point A, B or C? How do you know?
C
A
B
G. Match the scales used to measure Earthquakes.

Richter Scale
Moment Magnitude Scale
Modified Mercalli Scale


Ranges from 1-12, based on a person’s observations of the
intensity of the ground shaking and damage to areas, poll in mail
Most well known scale, but is no longer used
Gives a measure of the amount of energy released by an
Earthquake
H. How has seismic waves led to scientists discover of the Earth’s interior? (pg 507b & Fig 37)
VII. Volcanoes (pg -514)
A. What is a volcano?
B. Label the parts of a volcano to the right.
C. Volcanoes erupt explosively or quietly,
depending on the characteristics of the magma.
Compare these terms.
a. Quiet eruption:
b. Explosive eruption:
D. Where are most volcanoes found?
E. What is a hot spot? (pg 513)
F. Does a hot spot move?
G. Fill in the table.
Type of
volcano
Shield Volcano
Yes
How it is formed
or
No
Type of Eruption (s)
Picture
Composite
Volcano
Cinder Cone
Volcano
H. Match the term with the definition
 _____ Batholiths
 _____ Sill
 _____ Dike
 _____ Volcanic neck
A. Magma that hardens in the pipe of a volcano
B. Large, mass of intrusive igneous rock, (core of the
Sierra Nevada’s)
C. Magma squeezes into a horizontal crack between
rock layers and hardens
D. Magma squeezes into a vertical crack between
rock layers and hardens