Study Guide: The Restless Earth – Lessons 3, 5, and 6 – {Earthquakes}
Lesson 3: Mountain Building (Pages 218 & 219, 222 &223)
Teton
Mountains
Mountains Formed by Folding
Mountains Formed by Faulting
Volcanic Mountains
Over millions of years, fault movement can change a flat plain into a towering mountain range.
Fault - Block Mountains such as the Teton Mountains in Wyoming form by faulting.
Mountains can also form when deformation of rocks occurs when they change shape under the stress of
compression. Geologists use the terms anticlines and synclines to describe upward and downward folds in rock
layers. A fold that bends upward into an arch is called an anticline. A fold in rock that bends downward
in the middle to form a bowl shape is called a syncline. When melted rock erupts onto the Earth’s
surface volcanic mountains form.
Three Kinds of Faults (Pages 220 & 221)
*Type of fault: Transform Boundary or Strike-Slip
*Stress Force: Shearing
*Movement along fault: The blocks grind alongside each
other moving in opposite directions.
Type of Fault: Normal
Stress Force: Tension
Movement along Fault: The hanging wall
moves down.
*Type of Fault: Reverse
*Stress Force: Compression
*Movement along Fault: The hanging
wall moves up.
Lesson 5: Earthquakes (Pages 240 – 244)
*Earthquakes are ground movements that occur when blocks of rock in the Earth move suddenly and release energy.
Epicenter
1. Label the epicenter and focus on the diagram to the right.
2. What is the focus of an earthquake?
The focus is where movement occurs along
a fault releasing energy. The focus is usually
underground.
Focus
3. What is the epicenter of an earthquake?
The point on the Earth’s surface directly above the
focus is called the epicenter.
4. Where do most earthquakes take place? Explain why.
Most earthquakes occur along plate boundaries. That is where
subduction, sea floor spreading, mountain building, and transform
boundary / strike-slip movements take place.
5. When is more energy released by a fault, when the fault slips easily and frequently or when it gets “stuck”
for a long period of time and then snaps free suddenly? (Investigating Plate Movement at Faults Lab)
Fault Line
Increased Resistance = More Stress = Sudden Movement (Rupture) = More
Energy
Effects of Earthquakes (Page 244)
6. What are tsunamis, and how do they form?
A tsunami is an unusually large sea wave produced by faulting of the seafloor or an
undersea volcanic eruption.
Animation Link:
http://www.pbs.org/wnet/savageearth/animations/tsunami/main.html
Lesson 6: Measuring Earthquake Waves
7. Identify the different seismic waves by filling in the boxes under each diagram with their correct names.
(Pages 256-257)
These body waves travel straight outward from the focus compressing and expanding
causing the rocks to move back and forth. These waves reach the seismograph station first.
Primary Waves
These body waves vibrate from side to side and up and down as they travel through the rocks
and ground. These waves reach the seismograph station second.
Secondary Waves
These seismic waves travel along the Earth’s surface are the slowest moving. They cause the
ground to roll up-and-down and move side-by-side.
Surface Waves
Locating the Epicenter of an Earthquake (Pages 258 & 259)
8. Fill in the blanks below.
Location of an Epicenter
Seismogram
A seismologist is a geophysicist that study’s earthquakes. In order to locate the epicenter of an
earthquake, a seismologist needs to examine seismograms recorded by three different
seismograph stations. On each of these seismograms, seismologists have to measure the S - P time interval (in
seconds or minutes). The S - P time interval is the amount of time that passes between the arrival of the P
wave and the subsequent S wave. This interval will then be used to determine the distance the
waves have traveled from the origin to that station. This interval determines the distance the waves have
traveled, but gives no indication of the direction from which they came. The seismologist only
knows that the earthquake took place somewhere along a circle having a radius equal to the distance indicated.
That is why information from three different seismograph stations is necessary to locate the earthquake’s
epicenter.
If the S – P Time Interval is 4 minutes,
what is the distance of the epicenter
from the seismograph station?
A.
B.
C.
D.
2200 km.
2300 km.
2600 km.
2800 km.
9. Which of the following statements is supported by the World Earthquake Activity graph below?
A.
B.
C.
D.
The most earthquakes occurred in 1991.
The fewest earthquakes occurred in 1986.
There were more earthquakes in 1980 than in 1986.
The amount of earthquakes has increased over time.
The Richter and Mercalli Earthquake Scales (Pages 260 & 261)
10. When an earthquake has a magnitude of 7.0 according to the Richter Scale, what types of observable
damage will you see according to the Mercalli Scale?
Many structures destroyed, and the ground is badly cracked.
11. The Mercalli Scale indicates that a tremor was noticed by many people, but the people often don’t realize it
is an earthquake. What would the magnitude of this earthquake be according to the Richter Scale.
The magnitude of the Earthquake would be 3.5 on the Richter Scale.
12. An aftershock occurs several hours after an earthquake and is felt by everybody. Many people run outdoors.
Furniture moves and items fall off of shelves, but overall only slight damage occurs. What number would
this earthquake rank on both the Mercalli and Richter Scales?
The earthquake would register a 6 (VI) on the Mercalli Scale and a 4.5 on the
Richter Scale.
Factors That Determine the Effects of an Earthquake (Pages 262 & 263)
http://dsc.discovery.com/guides/planetearth/earthquake/interactive/interactive.html
 Magnitude and Duration of the Earthquake (How strong the earthquake is and how long it lasts.)
 Local Geology of the Rocks and Soil of the Location
Types of Ground
Coastal ground quality
varies. When near
water, there are many
dangers to consider.
Loose, gravely soil.
Prepare to go deep
for support.
Building along a fault
zone has its risks but is
often unavoidable.
Stable, solid ground such as solid bedrock
seems safest, but in a quake-prone area, all
construction is a calculated risk.
 Distance from the Epicenter (Surface waves decrease in size and energy the farther they travel.)
 Building Construction
Construction Methods
Reinforced Building
Metal strapping
materials give
concrete and masonry
structures more
tensile strength.
Mass Damper
Active Tendon Systems
Sensors notify a computer that
the building is moving. Then the
computer activates devices to
shift a large weight to counteract
the movement.
A weight is placed in the roof
of a building. Motion sensors
detect building movement
during an earthquake and send
messages to a computer. The
computer then signals controls
in the roof to shift the mass
damper to counteract the
building’s movement.
Base Isolation
Allows a structure’s foundation and
the ground move as one, minimizing
the forces on the building itself.
http://www.sciencelearn.org.nz/contexts/earthquakes/sci_media/video/how_base_isolation_originated