Transcript Volcanoes and Earthquakes

Volcanoes and Earthquakes
Based on Discover God’s Creation,
chapter 4-1 & 4-2
By Rebecca Fraker
A few notes
This is a large slide show. It would be better
to show it in several parts.
This slide show includes animations, video
clips, and links to websites.
Be careful where you click! If the pointer is
on a link, your computer will try to take you
to the website.
Part 1: Volcanoes
• Volcanoes are formed
when magma, the
melted rock of Earth’s
mantle, pushes up
through the crust onto
the surface.
• Volcanoes form on
both land and in the
ocean.
Parts of a volcano
Pipe or tube
Parts of a volcano
• The vent of a volcano is an opening in
Earth’s crust.
• From the vent, a tube or pipe serves as a
pathway from the mantle to the crust and
allows magma to move up and out of the
vent.
Parts of a volcano
• Lava is magma that reaches the surface.
Lava can be thin and almost watery or
thick like cookie dough.
Lava & Magma
• As lava cools it crystallizes to form rock.
• When it cools quickly, it has a smooth texture
such as obsidian.
• When it cools slowly the rocks are coarser.
• Sometimes gasses create “foamy” lava that
cools into rocks called pumice and scoria.
obsidian
granite
scoria
pumice
Volcanoes
• Volcanoes usually
form near the
boundaries of Earth’s
plates.
• The Ring of Fire is a
region of heavy
volcanic activity that
surrounds the Pacific
Ocean.
Eruptions
• Volcanoes also differ in the way they erupt.
• In some volcanoes the lava flows out of cracks
called fissures. These eruptions do not build
mountains but form broad, spreading layers of
lava.
• Other volcanoes build mountains as they erupt.
When lava flows out of the vent and cools, a
bowl-shaped crater often forms around the vent.
• As new material flows over the top, a cone
builds up.
Kinds of Volcanoes
• Three kind of volcanoes form mountains:
– Shield volcanoes
– Cinder cones
– Composite volcanoes
Shield Volcanoes
• Shield volcanoes are the largest type of
volcano.
• They are broad with gently sloping sides.
• They do not have violent eruptions; lava
flows out slowly.
• The Mauna Loa volcano, perhaps the
largest active volcano on Earth, is a shield
volcano.
Examples of shield volcanoes:
Mauna Loa
Volcano in Hawaii
Cinder Cones
• Cinder cones are the smallest type of volcano,
usually less than 1000 feet high.
• They form when pieces of lava blow out of a
volcano’s vent.
• Unlike shield volcanoes, cinder cones have very
steep sides.
• In 1943, Paricutin, a volcano in Mexico,
erupted.
• In the first day, a cone of over 130 feet high
formed, and within five days it was over 300
feet high. Two years later, this volcano was
more than 1300 feet high.
Examples of
Cinder cones
Paricutin in Mexico
Composite Volcanoes
• Mount St. Helens in the United States is a
composite volcano.
• These volcanoes have alternating layers
of lava and ash.
• Lava quietly flows out for a time.
• When the lava stops flowing, a plug forms
in the vent. In this condition, the volcano
may stay inactive for many years.
Composite volcanoes
• When a composite volcano again becomes
active, there is no place for magma and steam to
go.
• As pressure within the volcano builds, there is
an explosion that blows out the plugged vent.
• Such eruptions release tremendous power.
• The eruption of Mount St. Helens blew away
most of the mountain’s north side.
Examples of composite
volcanoes
Mount St. Helens before eruption
And afterwards, in 1982
Some products of volcanic eruptions
Steam and gases
lava
Fine ash
rocks
Famous eruptions
• Volcanic eruptions have had a dramatic
impact on the Earth’s surface and on the
lives of people and cultures.
• Following are accounts and pictures of
some of the more famous eruptions.
Mount Krakatoa
• So much pumice was released onto the
ocean’s surface from the eruption of
Krakatoa in 1883 that sailors were able to
walk 2 miles from their ship to the shore
on top of the floating pumice!
Krakatoa
before
and after
Krakatoa
• A volcanic island of Indonesia
between Sumatra and Java. A
momentous volcanic explosion
on Aug. 23, 1883, blew up most of
the island and altered the
configuration of the strait; it
caused a tsunami that killed more
than 36,000 people along the
nearby coasts of Java and
Sumatra.
• The explosion is classed as one
of the largest volcanic eruptions
in modern times; so great was the
outpouring of ashes and lava that
new islands were formed, and
debris was scattered across the
Indian Ocean as far as
Madagascar. Since then there
have been several lesser
eruptions.
Mt. Vesuvius
• POMPEII, MT. VESUVIUS, ITALY
In 79 AD, Mt. Vesuvius erupted an
enormous volume of pumice and ash.
This material flowed very quickly
down the side of the volcano as hot
ash flows. The ash flows covered the
Roman city of Pompeii in a few
hours. Many people were trapped by
the hot ash. Almost the entire
population of the city was killed.
Pompeii and Mt. Vesuvius
• Pompeii is undoubtedly one of the
world's best known archaeological
sites. Its fame comes from its dramatic
destruction and extraordinary
preservation as a result of an eruption
of Mount Vesuvius.
• On February 5, A.D. 62, Pompeii was
at the epicenter of a severe
earthquake that caused
considerable structural damage to
buildings and the infrastructure of
the city. It is clear that the process of
repair and redevelopment was slow
and extensive.
Pompeii
• On August 20, A.D. 79, Pompeii was rocked
by more earth tremors. Springs in the area
dried up.
• The ancient Pompeiians did not recognize
that these were signs of the imminent
eruption of Vesuvius. Therefore when the
volcano went off between noon and 1pm on
August 24, it caught everyone by surprise.
• According to Pliny the Younger, a 12-mile
high cloud of ash and rock was thrown into
the air, blocking out the sun.
• By chance, the wind was blowing from the
northwest, so when the volcanic matter
began to fall, it was blown in the direction of
Pompeii, Herculaneum and other sites to the
southeast.
• The eruption produced total darkness, as
well as electrical discharges from
atmospheric disturbances.
• Ash, pumice, and rock fell, initially with a
low density. This piled up in streets, on
rooftops, and fell in through every open
space such as windows.
• Some roofs collapsed under its weight and
falling debris may also have caused injury.
•
This phase of the eruption
continued for the rest of
the day. People wandered
around in darkness,
pushing their way through
pumice and debris, which
was piling up. Some may
have tried to escape, while
others decided to wait it
out. Surely no one had
experienced such a
catastrophe before so they
did not know what to
expect from it.
•
Shortly after midnight,
ground surges of magma
and volcanic mud began
as well as pyroclastic
surges, avalanches of
noxious gases and ash
rushing from the cone of
Vesuvius with terrific force
at over 100 kilometers an
hour
Pompeii
•
Herculaneum, which was situated at the base of
Vesuvius, was hit with a surge and entombed in volcanic
mud. Several pyroclastic surges roared toward Pompeii
but were stopped from doing too much damage by the
northern city wall right behind our city block. At about
7:30 am, enough pumice stones and debris had piled up
that a pyroclastic surge finally rolled up over the top of
the city wall, shearing off any buildings that were not
already buried by volcanic matter. All people still present
in the city died instantly.
• Thousands of people died within the city during the
eruption. Many more were probably killed in the
surrounding landscape as they tried to flee, but little
archaeological work has been done on Pompeii's
hinterland. A powdery deposit followed the most
destructive surge and when the eruption finally ceased
late on August 25, only the largest structures in the city
such as the Amphitheater and the Grand Palaestra were
probably identifiable.
• Pompeii and Herculaneum were to remain buried for around
1,700 years. Survivors of the eruption must have decided that
rebuilding on the site was out of the question, but some
researchers claim that there were signs that for a time people
lived in the ruins, and a fishing community probably existed at
the mouth of the nearby river Sarno.
• During the later Roman period, and into the Middle Ages,
Pompeii was forgotten. In March 1748, a surveying engineer,
was sent by King Charles III of Spain with a mission to supply
the Spanish court with ancient statues and other treasures. He
learned that at the place called La Cività (what the people of the
country called this area) objects of antiquity had been found.
The excavations at Pompeii have continued ever since.
Mosaics, pottery, and casts of
people buried in the Mt.
Vesuvius eruption about 80
years after Jesus’
crucifiction.
• CRATER LAKE, OREGON
Crater Lake erupted about
7770 years ago. It was a
gigantic eruption of ash
flows. So much material
erupted that the top of this
volcano collapsed.
• This formed a great hole
where the top of the
volcano had been. The hole
was gradually filled with
water from rainfall and
melting snow. A new
eruption in the middle of
the lake formed a tiny
cinder cone volcano, now
called Wizard Island.
PARICUTIN, MEXICO
A cinder cone grew to a height of more than
1500 feet. It first began in a cornfield in 1943.
The volcano grew and erupted a lot of lava,
eventually covering more than 10 square miles.
It frightened farmers, but enough warning was
given for most of the local population to escape
without harm.
Mt. Pelée on Martinique
• The island of Martinique lies in the Caribbean
Archipelago between the Atlantic Ocean and the
Caribbean Sea. Mt. Pelée, located on the
northern side of the island, proved to be the
deadliest volcano of the 20th century.
Mt. Pelée
• Three days before the
eruption, the rim of the
volcano crater collapsed,
sending scalding water down
the nearby River Blanche.
Collecting debris along the
way, the mudflow buried
everything in its path before
reaching the sea.
• The impact created a nearly
ten-foot-high (three-meterhigh) tsunami, flooding the
low-lying areas around St.
Pierre.
Mt. Pelée
• Mt. Pelée erupted at 7:50 a.m.
on May 8, 1902. A giant black
plume darkened the sky, while
a pyroclastic flow—a
superheated cloud of hot ash,
toxic gases, and magma
fragments—raced down the
volcano's sides at hurricaneforce speeds.
• Within minutes, the city of St.
Pierre had been destroyed, its
30,000 inhabitants dead.
Mt. Pelée
• One of only two survivors, 25-year-old
Louis-Auguste Cyparis was in jail when
the volcano erupted the morning of May
8, 1902. Cyparis had been moved to
solitary confinement in an underground
cell. The thickness of the walls and
absence of windows sheltered him from
the most deadly effects of the eruption,
but Cyparis was severely burned by hot
air and ash. In great pain, he managed to
survive trapped in the cell for four days
until scientists exploring the ruins
rescued him.
Some resources
http://volcano.und.nodak.edu/vwdocs/current_volcs/curre
nt.html
Information on currently erupting volcanoes around the
world, with links to each site.
http://www.geo.mtu.edu/volcanoes/
Michigan Technological University - volcano sites from
around the world.
http://vulcan.wr.usgs.gov/home.html
The US Geological Survey Cascades Volcano
Observatory. Excellent information on US volcanoes, as
well as plate tectonics and geologic hazards.
Part 2: Earthquakes and Tsunamis
• Earthquakes are shock waves resulting
from movements in Earth’s crust. They
have occurred throughout the history of
the world.
• Scientists estimate that worldwide, over
800,000 earthquakes occur each year.
• Most earthquakes are too small to be felt,
but they can be detected by special
equipment.
Where do earthquakes take place?
• Earthquakes often happen near boundaries of plates and at
faults, or cracks in the plates.
• As the plates move, pressure builds up in the rocks along
the fault.
• If movement stops, the energy remains stored in the rocks.
• If movement continues, the rocks can no longer hold their
position and suddenly they slip past each other.
• To illustrate this, try bending a small branch you have taken
from a bush or tree. It will bend so long, and then snap.
Faults
• Only one side of a fault moves. The moving
plate can either push up, slip down, or move
horizontally.
• There are three
kinds of faults:
– Normal faults
– Thrust faults
– Strike-slip faults
(transform faults)
Normal Faults
• The moving plate slips below the
stationary plate.
• The fault that runs through the Rift Valley
of Africa is an example of a normal fault.
Thrust Faults
• The moving plate moves up and over the
stationary plate. Chief Mountain in
Montana is an example of a thrust fault.
Thrust faults
Strike-Slip Faults
• The moving plate slides past the stationary
plate. The San Andreas fault in California
is a strike-slip fault.
Strike-Slip faults
Focus and Epicenter
• The point where the actual slip happens is
the focus of the earthquake. It is usually
deep within the earth.
• Energy waves travel out in all directions
from the focus.
Focus and Epicenter
• The epicenter of an
earthquake is the point
on the surface of the
ground directly above
the focus.
• If you were standing at
this point, you would
be the first to feel the
earthquake.
Earthquakes Today
• Today we have more than 4,000
seismograph stations in the world that
record 12,000 to 14,000 earthquakes per
year—that’s about 35 a day!
Some earthquakes
• Here are some earthquakes that have
caused great loss of life and great
damage:
– China, 1920, 7.6, 180,000
– China, 1976, 7.6, 250,000
– Japan, 1923, 8.3, 140,000
– Peru, 1970, 7.7, 70,000
– Mexico, 1985, 8.1, 10,000
– Afghanistan, 1998, 6.9, 5,000
San Francisco Earthquake
• "San Francisco and Oakland are
becoming as Sodom and Gomorrah, and
the Lord will visit them. Not far hence they
will suffer under His judgments."--Ms 30,
1903. Ellen G. White
Other quotes:
• On April 16, 1906, two days before the San Francisco earthquake,
Mrs. White said that,
• “While at Loma Linda, California, April 16, 1906, there passed
before me a most wonderful representation. During a vision of the
night, I stood on an eminence, from which I could see houses shaken
like a reed in the wind. Buildings, great and small, were falling to
the ground. Pleasure resorts, theaters, hotels, and the homes of
the wealthy were shaken and shattered. Many lives were blotted out
of existence, and the air was filled with the shrieks of the injured
and the terrified. The destroying angels of God were at work. One
touch, and buildings, so thoroughly constructed that men regarded
them as secure against every danger, quickly became heaps of
rubbish. There was no assurance of safety in any place. I did not
feel in any special peril, but the awfulness of the scenes that
passed before me I cannot find words to describe. It seemed that
the forbearance of God was exhausted and that the Judgment day
had come. “ (Testimonies, Vol. 9, pp. 92-93)
• Two days later, on April 18, 1906, a devastating earthquake struck
San Francisco
Where are the faults in the United
States?
San Andreas
Fault, California
New Madrid Fault,
Mississippi River Valley
Where are faults in the United
States?
California
Earthquake fault lines
• Earthquakes in the
United States have
happened in Hawaii,
Alaska, California,
and the Mississippi
River Valley.
Alaska is the most earthquake-prone state
and one of the most seismically active regions
in the world. Alaska experiences a magnitude
7 earthquake almost every year, and a
magnitude 8 or greater earthquake on average
every 14 years.
Earthquake Facts
•
•
•
The largest recorded earthquake in the
United States was a magnitude 9.2 that struck
Prince William Sound, Alaska on Good Friday,
March 28, 1964 UTC.
The largest recorded earthquake in the
world was a magnitude 9.5 (Mw) in Chile on
May 22, 1960.
The earliest reported earthquake in
California was felt in 1769 by the exploring
expedition of Gaspar de Portola while the
group was camping about 48 kilometers (30
miles) southeast of Los Angeles.
Earthquake Facts
•
•
It is thought that more damage was done by
the resulting fire after the 1906 San Francisco
earthquake than by the earthquake itself.
Each year the southern California area has
about 10,000 earthquakes. Most of them are so
small that they are not felt. Only several hundred
are greater than magnitude 3.0, and only about
15-20 are greater than magnitude 4.0. If there is
a large earthquake, however, the aftershock
sequence will produce many more earthquakes
of all magnitudes for many months.
Even a pool can be a seismometer
• A seiche (pronounced SAYSH) is what happens
in the swimming pools of Californians during and
after an earthquake. It is "an internal wave
oscillating in a body of water" or, in other words,
it is the sloshing of the water in your
swimming pool, or any body of water, caused
by the ground shaking in an earthquake.
• It may continue for a few moments or hours,
long after the generating force is gone. A seiche
can also be caused by wind or tides.
Earthquake facts
1.
•
•
The magnitude of an earthquake is a measured value of
the earthquake size. The magnitude is the same no
matter where you are, or how strong or weak the shaking
was in various locations.
The intensity of an earthquake is a measure of the
shaking created by the earthquake, and this value does
vary with location.
From 1975-1995 there were only four states that did
not have any earthquakes. They were: Florida, Iowa,
North Dakota, and Wisconsin.
The swimming pool at the University of Arizona in Tucson
lost water from sloshing (seiche) caused by the 1985
M8.1 Michoacan, Mexico earthquake 2000 km (1240
miles) away.
New Madrid Fault
Earthquakes occur in the central portion
of the United States too! Some very
powerful earthquakes occurred along the
New Madrid fault in the Mississippi
Valley in 1811-1812. The effects of
shaking from these magnitude 8+
earthquakes caused church bells to ring
in Boston, Massachusetts, nearly 1600
km (1000 miles) away.
China Earthquake Facts
1. The world's deadliest recorded earthquake
occurred in 1556 in central China. It struck
a region where most people lived in caves
carved from soft rock. These dwellings
collapsed during the earthquake, killing an
estimated 830,000 people. In 1976 another
deadly earthquake struck in Tangshan,
China, where more than 250,000 people
were killed.
2. The earliest recorded evidence of an
earthquake has been traced back to 1831 BC
in the Shandong province of China, but there is
a fairly complete record starting in 780 BC
during the Zhou Dynasty in China.
Earthquakes can cause tsunamis
• If an earthquake occurs under the ocean, a large
wave called a tsunami may form.
• Tsunamis can travel at nearly 400 mph across the
ocean.
• Some tsunamis cause waves several hundred feet
high. When they hit land, they are extremely
destructive.
Tsunamis
• In the last few
years, several
tsunamis have
caused
hundreds of
thousands of
deaths as well
as massive
property
destruction
worldwide.
Earthquake & tsunami Summer
2006
• Off the island of Java, Indonesia, an earthquake rumbled
under the ocean on July 17, 2006. The motion triggered
a tsunami that struck the island about an hour later. At
5:07pm local time on July 17 a 10 foot high tsunami hit
the Indonesian island of Java.
• According to news reports, the area most devastated
was the area around Pangandaran, located about 25
miles (40 kilometers) west of the city of Cilacap. This
area is a fishing community and resort area. Larger
structures withstood the tsunami, but many smaller
buildings and homes were washed away.
• The death toll has now reached 525 people with 273
people still missing. More than 35,000 people were
displaced by the wave.
……summer 2006
• According to the U.S. Geological Survey, the
tsunami was caused by a 7.7 magnitude
earthquake with an epicenter about 155 miles off
the coast of the island. The earthquake occurred
in a shallow part of the boundary between the
Australia Plate and the Sunda Plate. The two
tectonic plates meet offshore of the island of
Java. Java is located to the north of the Java
trench, the surface expression of a subduction
zone.
(summer) July 19, 2006 tsunami
December 2004 Tsunami
• The video clips on this website were taken
by ordinary people with ordinary video
cameras. These people were trapped in
the tsunami.
• http://www.asiantsunamivideos.com/
December 2004 Tsunami
(article by Wikipedia)
The 2004 Indian Ocean earthquake, known by the scientific
community as the Sumatra-Andaman earthquake, was an
undersea earthquake that occurred at 00:58:53 UTC (07:58:53
local time) December 26, 2004, with an epicentre off the west
coast of Sumatra, Indonesia. The earthquake triggered a series
of devastating tsunamis that spread throughout the Indian
Ocean, killing large numbers of people and inundating coastal
communities across South and Southeast Asia, including parts
of Indonesia, Sri Lanka, India, and Thailand. Although initial
estimates have put the worldwide death toll at over 275,000
with thousands of others missing, recent analysis compiled lists
a total of 229,866 persons lost, including 186,983 dead and
42,883 missing. The figure excludes 400 to 600 people who are
believed to have perished in Myanmar which is more than that
government's official figure of only 61 dead.
(article from Wikipedia)
• This catastrophe is one of the deadliest disasters in modern
history. The disaster is known in Asia and in the international
media as the Asian Tsunami.
• The magnitude of the earthquake was originally recorded as 9.0
on the Richter scale, but has been upgraded to between 9.1
and 9.3. At this magnitude, it is the second largest earthquake
ever recorded on a seismograph. This earthquake was also
reported to be the longest duration of faulting ever observed,
lasting between 500 and 600 seconds, and it was large enough
that it caused the entire planet to vibrate at least half an inch, or
over a centimetre. It also triggered earthquakes in other
locations as far away as Alaska.
• The earthquake originated in the Indian Ocean just north of
Simeulue island, off the western coast of northern Sumatra. The
resulting tsunami devastated the shores of Indonesia, Sri
Lanka, India, Thailand and other countries with waves up to
30 m (100 ft). It caused serious damage and deaths as far as
the east coast of Africa, with the furthest recorded death due to
the tsunami occurring at Port Elizabeth in South
Africa(5,000 mi) away from the epicentre.
This is a very short video clip. It was taken by a tourist on the 3rd floor of a hotel.
This video clip from the 2004 tsunami shows the earthquake first, which then
causes the tsunami to start. About 3 minutes.
December 2004 Tsunami
Seismographs
• A seismograph records the
shock waves created by
earthquakes.
• A seismograph consists of
a rotating drum that moves
a strip of paper at a
constant speed. Resting
on top of the paper is a
pen that draws a straight
line as the paper moves
beneath it.
• Vibrations caused by
earthquakes waves make
the pen scribble on the
paper
Seismograph
Chinese earthquake
detector
Three kinds of shock waves:
• An earthquake produces three kinds of
shock waves:
– Primary waves
– Secondary waves
– Surface waves
They are also known as “P-waves”, “S-Waves”,
and “L-Waves”.
Primary Waves
• Primary Waves (P-Waves) are
like those made by pushing a
Slinky in a forward direction.
They are created by the backand-forth movements of rock
that makes up the crust.
• Primary waves travel more
than 28,000 mph and are the
first to reach the seismograph.
• But although P-waves travel
fast, they DO NOT cause
damage on Earth’s surface.
Primary Waves
Secondary Waves
• Secondary Waves (S-Waves) are created
by the up-and-down movements of
underground rock.
• S-Waves are the second earthquake wave
to reach the seismograph and also DO
NOT cause surface damage.
Surface Waves
• Surface waves (L-Waves) are created on the
surface of the earth.
• They move more slowly than the other type of
waves and are created by the movement of the
S-waves.
• L-waves are similar to the ripples created when
you throw a large rock into a pond of lake.
• They make earth’s crust move and are the
waves that cause earthquake damage.
Surface Waves
Key Concepts:
• Body waves travel through the earth
• there are two types of body waves
– P-waves (Primary waves) and S-waves (Secondary waves) are body
waves
• P-waves arrive first and are small
• S-waves arrive second and are bigger
• Surface waves arrive last, and they are the biggest
– The particles do not travel with the wave, they return to their original
position
• P-waves move particles parallel to the direction of wave propagation
• S-waves move particles perpendicular to the direction of wave
propagation
• P-waves can travel through solids and liquids
• S-waves can only travel through solids
Charles Richter
• In the 1920s when scientists began to study earthquakes,
Charles Richter, a physics student, was given the job of
studying the readings of seismographs to determine the
epicenters of earthquakes.
• He had to describe the size and strength of each
earthquake. By 1935, he developed a better method of
measuring earthquakes.
• He used the seismograph readings and compared the
largest surface waves of each earthquake. He assigned
each one a number from 1 to 10. Each step was ten
times the strength of the step before.
• So a magnitude 3 earthquake would be 1 x 10 x 10, or
100 times a magnitude 1 earthquake.
What is a small earthquake?
• Earthquakes measuring 4 or less on the
Richter scale are considered small.
• Small earthquakes occur more than 700
times a day.
• Large earthquakes, those measuring
greater than 7 on the Richter scale, occur
less frequently.
• Usually fewer than 20 large earthquakes
happen each year throughout the world.
Predicting Earthquakes
• So far, scientists have been able to predict
only where most earthquakes will probably
occur, not when.
Connections Between Volcanoes
and Earthquakes
• In 1980, when Mt. St. Helens, a volcano in Washington
state, erupted it showed the relationship between
earthquakes and volcanoes. Mt. St. Helens is along the
Ring of Fire.
• From 1975 to 1980, more than 45 earthquakes occurred
on or near the mountain.
• In the month before the eruption, there were as many as
15 earthquakes happening there each hour.
• The earthquakes culminated in a large-magnitude
earthquake just as the volcano erupted.
Connections between earthquakes and tsunamis
• This animation shows the
connection between
earthquakes and tsunamis
in the December 2004
event. On Sunday 26
December 2004, a
Magnitude 9.0 earthquake
occurred off the West
Coast of Northern
Sumatra in the Indian
Ocean. The world’s
strongest for forty years,
it generated a massive
tsunami that is known to
have claimed around
300,000 lives. Animation
credit: NOAA