What is happening in this photograph??
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Transcript of What is happening in this photograph??
What is happening in this photograph??
What do volcanic eruptions reveal about the earth’s
interior??
What do you think the darker material floating on the molten
lava is??
Earthquakes and Volcanoes
Chapter 7
Section 1 Earthquakes
Objectives:› Describe what happens during an
earthquake› Explain the difference between an
earthquake’s focus and epicenter› Compare and Contrast the three
types of waves produced by earthquakes
Skills Warm-up
This Just In ……› Imagine you are listening to the
radio when the announcer says that a 5.8 earthquake has occurred in Alaska.
› How do earthquakes happen??› What does the 5.8 mean??
Earthquakes Movements of the
earth’s crust that occur when _______________and release stored _________
Energy quickly travels out in ________ from the point of breakage
Energy can ______ and ________ rock and soil
Most occur at depths less than ____________ because the rocks are brittle
Earthquakes Most earthquakes
result from movements of the earth’s crust along ___________
Faults are __________ in the earth’s crust
The 2 sides move in _________ _______
and earthquakes occur
Physics of Earthquakes As the 2 sides of a
fault move past each other, sometimes the rocks ________, _______ and become __________
Tremendous ________ builds up in these areas
Physics of Earthquakes ______ _____ – amount
of stress a material can absorb› Example – rubber
band stretched too far
When rocks are strained beyond elastic limit – _______ and ________ past each other
Huge amount of __________ released.
Physics of Earthquakes As rocks break and
move, __________ _______ is transformed into _______ _________
_______ ________ – the vibrations produced by earthquakes
3 Types:› ____________› ____________› ____________
Primary Waves P Waves – _________
seismic waves _____________ - the
material through which the wave is travelling moves in the _________ direction as the wave
___________________________the earth in direction of the wave
Secondary Waves S Waves - second
waves to arrive at a given point – _____ _________
__________ – material moves at ______ ________to the wave direction
Like the up-and-down movement of a rope
Surface Waves ____________– when P
and S waves arrive at earth’s surface
Cause the earth’s surface to __________ ____________________________________________________________
Cause the __________ damage during an earthquake
Activity Earthquakes movie
Focus vs. Epicenter _______ – area along a
fault where _________ ______ ______________ – where earthquake begins› Seismic waves travel
out in __________ from the focus
___________ – point on earth’s surface directly __________________ – strongest shakes felt here
Detecting Seismic Waves ________________ -
detect and record seismic waves
Have a pen attached to a weight and a sheet of paper on a revolving drum
Seismic waves cause the pen to _______ and record a wavy line on paper
_________ of the peaks indicates the _________ of the earthquake
Locating an Epicenter P, S, and L waves
travel at _________ _________
So, they reach a seismograph at __________ _________
The difference between the arrival times of the waves helps scientists find the _______________
Locating an Epicenter Calculated distance to
the epicenter becomes the ________ of a circle that is plotted on a map
Epicenter lies ______________ on the circle
Plotting circles from ___ ____________ _______ _________ pinpoints the epicenter – why do you need 3 stations??
Rating Earthquakes _______ _________–
compares the size of earthquakes using data from seismograph stations› Each increase of _____
magnitude number equals an increase of ______ in ground motion
› A magnitude 7 earthquake causes 10 times more damage than a magnitude 6 and 100 times more damage than a magnitude 5
Rating Earthquakes ________ ________–
measures the effects of an earthquake on › ________________› ________________› ________________› ________________
Data gathered from people who have experienced the quake are used to determine an intensity value for their location
Activity Comparing earthquake scales Textbook page 136
Earthquake Zones Most of the world’s
earthquakes occur along or near the edges of ________ ______________
At these spots, ______ is the greatest
3 Major earthquake zones:› 1. ________________› 2. ________________› 3. ________________
Ring of Fire Accounts for ______ of
world’s seismic activity
Goes all the way around the _________ _________
Includes east coast of Asia and west coasts of North and South America
Active spots in the U.S.› __________________› __________________
Mid-Atlantic Ridge Hypothesis – ________________
__________ is being made along the mid-Atlantic ridge
This causes many earthquakes
Mediterranean-Asiatic Belt
_____________ _________ are colliding
Causes very destructive _____________
Far from Plate Boundaries Small number of
earthquakes occur far from plate boundaries (strong)› ______________________
________________› ______________________
________________ Even quiet parts of
earth can conceal large amounts of ____________
Hidden Faults 1983 – Coalinga, Ca
(between LA and SF) Magnitude __________
earthquake Surprised scientists:
› __________________› __________________› __________________
Hidden Faults Team of scientists
studied what happened
Found several faults ___________ beneath
They were hidden inside of __________ in the earth
The determined these faults are ______ very active
Questions 1. Explain what causes earthquakes. 2. What is the difference between an
earthquake’s focus and epicenter? 3. How do the 3 types of seismic waves
differ? How are they similar? 4. Would using 4 seismograph stations
to locate the epicenter of an earthquake be any more accurate than using 3? Explain.
Lab Activity – How to Model the Richter Scale
Page 139 in Textbook
Section 2 EarthquakeEvidence
Objectives:› Describe some features produced by
earthquakes› Discuss factors that determine
earthquake damage› Explain what causes tsunamis› Make Inferences about ways to build
structures that could withstand major damage from earthquakes
Ground-Level Evidence Earthquake
evidence is sometimes preserved in ________ or ____________ changes to the ground
Strong earthquakes leave _________ evidence
Ground-Level Evidence At some faults changes
are _____ but ________________ – no earthquakes
____________ – slow, continuous, steady motion
Creep rate of 1 cm/year – ground levels would be displaced by 1 meter after __________
Can break structures
Landscape Evidence Powerful
earthquakes can cause ____________ damage
____________ earthquake of 1964 – ______ magnitude
Upheaval of >260,000 square km of ground
___________ moved sideways!
Landscape Evidence Earthquakes
affect poorly compacted sediments more:› __________› __________› __________
Slides Rapid down slope
movements of ________, ________, and _________
Can occur on a _______ or far away
Large sections of mountain may ________ and race downward
Some continue for ____________, destroying all in their paths (homes and roads)
Scarps Sudden earth
movements that _________ ________
Height depends on the _____ of material uplifted and the ___________ and ___________ of uplift
Fissures Long ________ in
rock or soil May extend for
_______ _____________
If fissures occur on hill or mountain – massive ____________ can occur
Factors of Earthquake Damage ____________ of
epicenter to ______________ area
Moderate quake in a crowded city causes _________ damage than a large quake in a desert
Factors of Earthquake Damage _______ ___ _________
where structures are built affects amount of damage
Soft, wet, loose soils can ___________ seismic waves
Buildings on more solid ground have better chance of survival
Factors of Earthquake Damage
Building ________ and _____________ affect damage
________ __________ buildings may move with and withstand ground motion
Brick and cement may ________ and _____________
Factors of Earthquake Damage __________ – an ocean
wave caused by ________________
__________ water – tsunamis are low and fast-moving
__________ water – they slow down and increase in height (30 meters)
Few structures survive a large tsunami
Earthquake Prediction Past – changes in
animal behavior and well levels
Now – seismologists look at› __________________› __________________› __________________
Loma Prieta Earthquake 1981- scientists
predict a quake is likely in the _____ _______mountains within ______ years
1988 and 1989 – moderate quakes identified as ___________
1989 – devastating earthquake in _______ ___________
Earthquake Safety If you live near an active fault – should
have an earthquake _______ ________› What to ______ during quake› Where to ________ after quake› How to ______________ if phones don’t work
In earthquake-prone areas – strict _________ ___ _________ laws are in place
Questions 1. What are some changes caused by
earthquakes? 2. What factors determine the amount
of damage caused by an earthquake? 3. Describe the hazards you might face
if an earthquake struck while you were:› asleep in bed› standing next to a tall building› at the beach› skiing
Activity Earthquake Webquest
Section 3Volcanoes
Objectives:› Describe how volcanoes form› Explain why volcanoes erupt› Compare the 3 main types of
volcanoes› Make a model of the structure of a
volcano
Skills Warm-up
Pressure Is Mounting› What happens when you blow up a balloon
or inflate a tire and put in too much air?› What happens when heat and pressure
build up in a closed space and the pressure is suddenly released?
› How might these pressure situations be similar to a volcano that is about to erupt?
Volcanoes Any opening in the
earth’s crust that has ________ _______ ______
Also, the mountain that builds up from _________ _________
Examples:› _______ – Japan› ______________ –
Washington state› _____________ - Sicily
Formation of a Volcano ________ (molten rock)
is under great ________ deep inside earth
Magma forms deep pockets called ________ ___________ in some places
If the __________ and _________ are great enough, magma will force its way up through earth’s crust
Formation of a Volcano The more heat and
pressure acting on magma – the more likely magma will force its way to the surface
_________ – magma that reaches the earth’s surface
__________ – when lava or other volcanic materials reach earth’s surface
Volcano Life ___________ – have
erupted in the past century
___________ – haven’t erupted in hundreds of years
___________ – haven’t erupted in thousands of years
Eruptive life may span _________ __ ________ ___ ______
Mount Popa - Myanmar
Parts of a Volcano _______ ___________ –
formed from large pockets of magma
When magma is hot or powerful enough, it makes its way toward the surface through ________ in the ________
Parts of a Volcano ________ – long, nearly
_______ ________ in the crust through which magma moves
Can be thousands of meters long and only a few meters wide
Magma travels through the pipe until it reaches a ________ on earth’s surface
Parts of a Volcano
__________ – steep, hollowed-out area surrounding a vent at the _______ of a volcano
Usually forms after a very _____________ eruption
Parts of a Volcano
________ – opening through which all volcanic material ________ ____ _______
Common at the tops of volcanoes, but may also be _______ ___ ________
Volcanic Eruptions Eruptions can be:
› __________________________________________
› __________________________________________
This is determined by:› __________________› __________________› __________________
Lava Flow _________ of lava that
flows from a vent Stream can be
_______ or spread out Some lava flows can
reach speeds of _________________
Lava cools and hardens as it moves
Example - __________
Volcanic Explosions Explosive volcanoes
give off ___________ _________
Debris is identified by ____________› Dust – size of flour
grain› Ash› Cinders› Bombs - > 64 mm
Activity
Types of Volcanoes Produced by
different types of volcanic eruptions and explosions
Named for its shape or structure:› __________________› __________________› __________________
Cinder Cone Volcanoes Form from the
products of _________ _____________
Ash, cinders, and other debris mound up around the vent, ___________ __ ______
Are ________ sloping at the top and _________ sloping at the base
Usually form from ____, ____________ magma
Shield Volcanoes Have ______, shield
like shapes Lava is _______ and
______ ______ away from the vent
As it cools down, it becomes thicker, slows down and collects.
Composite Volcanoes Contain alternating
layers of _________ _____ ____ _______
Usually formed from _______ ________ of eruptions
Have ______ tops but gently ___________ bases
Areas of Volcanic Activity Most earthquakes
and volcanoes occur along _______ ______________
Volcanic activity can often produce ___________________
As magma moves up, it may _________ rocks or ___________ overlying crust
Ring of Fire Encircles ______________ Major zone of both
_____________ and _______________
Ocean plates are ______________ and volcanoes occur in long chains
One major chain runs along the west coasts of _______ _____ _______ _____________
Oceanic Ridge Systems Earth’s _____________
volcanic zones Plates are moving apart
forming cracks called ___________
As magma rises through rifts, the _______________
Lava builds up forming underwater ___________
__________ is formed from volcanoes that have risen above the surface
Hot Spots Develop in parts of the
earth’s mantle that are _______ _____
They can be _______ from plate boundaries
As the hot spots melt the surrounding rock, the rock changes to _________ and rises to the surface
_________ ________ are formed over a hot spot
Great Vesuvius Eruption ________ __________ is
the only active volcano on the European mainland
It is located just outside _______, _______
It last erupted in ____ Most destructive
eruption was on August 24, AD. 79
Great Vesuvius Eruption Most people
probably didn’t know that the mountain was a volcano
It hadn’t erupted in _______________
But there was a ________ earthquake 17 years earlier
Great Vesuvius
Eruption Eruption rained hot
ash, mud, and stones on the residents of _____________
Many people did not survive – _______ ______
Town disappeared completely under _____ __________of ash and stone
Wasn’t rediscovered for ___________ years
Life on a Volcanic Island How does life develop on molten
rock? Moisture from _______ and ______
react chemically with exposed _________
Over time, ________ develops Wind, waves, and birds scatter
________, ______________ and _________
________ and _________ appear and break down rock
Ocean currents bring _________ life
Eventually there will be a ____________ of plants and animals
Surtsey, Iceland
Predicting Volcanic Eruptions
Sophisticated devices can monitor:› __________
accumulation› increased __________
activity› changes in
________________› gas ____________
Advances in photography and satellite imaging
Questions 1. What is a volcano? How does it
form? 2. Explain the differences between
shield volcanoes, cinder cones, and composite volcanoes.
3. Volcanic activity has been known to trigger tsunamis. How is this possible?
4. Draw a general diagram of a volcano. Label its main parts.
Activity Volcano Webquest
Activity Review sheets – quiz grade