Chapter 7 LESSON 2 & 3 Study Guide
TEST – Thursday 12/20/12
Lesson 2: Earthquakes
Vocabulary:
fault - a huge crack in Earth’s crust
at or below the surface, the sides of
which may show evidence of
movement.
aftershock – shaking of Earth’s crust after an
earthquake, usually not as strong as the first
earthquake.
focus - the point where an earthquake
starts as rocks in the plates begin to
slide past each other.
seismograph – a sensitive device (machine) that
detects the shaking of Earth’s crust during an
Earthquake.
seismic wave – a vibration that spreads
out away from a focus when an
earthquake happens.
magnitude – the amount of energy released by
an earthquake. It is measured using the
Richter Scale.
epicenter – the point on Earth’s
surface directly above the focus point
of an earthquake.
Know:
What is an earthquake and where do they
happen? D20-D21
An earthquake is a sudden trembling of the ground. Most earthquakes happen at the edges of
plates, where the plates meet. Plates may collide (crash into each other), slide past each
other, or pull apart. These movements can cause the rocks to bend and stretch until they
break, which causes the earth to shake.
What are normal faults, reverse faults, and strike-slip faults? D21
Fault
Normal Fault
Where produced
Divergent Boundaries
Reverse Fault
Convergent
Plates push together
Boundaries
Transform Boundaries Plates slide past each
other without moving
up or down.
Strike-slip fault
How produced
Plates pull apart
How rocks move
Rocks above the fault
surface move down.
Rocks above the fault
move upward.
Rocks slide past each
other in different
directions.
Explain primary waves, secondary waves, and surface waves. D22-D23
Primary waves – fastest seismic waves, the first to reach any faraway location after an
earthquake.
Secondary waves – seismic waves travel slower than primary waves. They are the second to
arrive at any faraway location after an earthquake.
Surface waves – waves that are produced by the shaking up and down of Earth’s surface, like
an ocean wave, or swaying from side to side. These movements cause structures (such as
buildings) built on the surface, to be torn apart.
Explain the difference between the Richter Scale and the Mercalli Scale. D25
Richter Scale – compares the energy of earthquakes using a rating scale of 1-10 depending on
the magnitude of the earthquake (how strong the earthquake is).
Mercalli Scale – is based on the amount of damage done at a given location. It is based on a
rating of I-XII. Example: did the earthquake shake dishes in the cabinet, or did the actual
building crack and fall down.
What is a tsunami? D23
A tsunami occurs when the focus of an earthquake is beneath the sea-floor. The seismic
waves can travel through the ocean causing a huge ocean wave.
How can you prepare for an earthquake? D26
- Take a first-aid and CPR course.
- Put together an earthquake kit that includes flashlights, batteries, radio, and a first-aid
kit.
- Make an emergency escape plan.
- Keep extra non-perishable food items and water in your house.
Lesson 3: Volcanoes
Vocabulary
vent - the central opening in a
volcanic area, through which magma
may escape.
cinder-cone volcano – a steep-sided cone
that forms from explosive eruptions of hot
rocks, ranging from particles to boulders.
lava – magma that reaches Earth’s
surface and flows out of a vent.
shield volcano – wide, gently sloped cone
that forms from flows of lava.
crater - a cuplike hollow that forms at the
top of a volcano, around the vent.
composite volcano – a cone formed from
explosive eruptions of hot rocks, followed
a flow of lava, over and over.
hot spot – a very hot part of the mantle,
where magma can melt through a plate
moving over it.
geothermal energy – heat from below
Earth’s surface.
Know:
How do volcanoes form? D30
A volcano is a place where molten rock, hot gases and solid rock erupt through an opening in
the crust. It is also the mountain built up by these materials.
Beneath every volcano is a source of magma. Magma rises to the surface through cracks in
the rock above it from the magma chamber. In time it reaches the surface and erupts through
a vent. Erupted materials cool and harden around the vent in a mound. After many eruptions
it can pile up into a big hill or even a mountain. This is a volcano. At the top of a volcano is a
cuplike hollow around the vent called a crater.
Where are volcanoes located? D31
Volcanoes occur in belts, or long lines. Most volcanoes occur along plate boundaries.
Over 80% of all land volcanoes are found on the Pacific Ring of Fire, and along the
Mediterranean Sea through Iran.
Some also form over hot spots. A hot spot is a very hot part of the mantle. As the plate moves
over a hot spot, magma melts up through the crust and forms a volcano.
How are the types of volcanoes alike and how are they different? D32-D33
All volcanoes are places where molten rock, hot gases and solid rock erupt through an opening
in the crust. The erupted materials cool and harden to form a mound, hill or mountain.
Cinder-Cone Volcano – has steep sides and forms form eruptions of hot rocks, ranging from
particles to boulders.
Shield Volcano – wide and gently sloped, it forms from flows of lava.
Composite Volcano – formed from explosive eruptions of hot rocks, followed by a flow of lava,
over and over.
What is the difference between active, dormant, and extinct volcanoes?
Active Volcano – is erupting now or has erupted recently.
Dormant Volcano – has not been active for a long time, but has erupted in recorded history.
“Sleeping.”
Extinct Volcano – has not erupted in recorded history.