Transcript Earthquake and Volcanoes - Grants Pass School District 7

This map shows only the known faults in Oregon.
Faults that have moved most recently are shown in red.
Earthquake and Volcanoes
Seismologist
I. Earthquakes
A. Earthquake: the shaking and
trembling that results from
the movement of rock
beneath the Earth’s surface.
1. Seismology – the study of
Earthquakes
2. Seismologist – geologist
that studies earthquakes
3. Stresses causing
earthquakes
a. Shearing
b. Compression
c. tension
Questions
1. ____________________________ is the study of
earthquakes.
2. A ___________________________ is a person who
studies earthquakes.
3. Stress at tectonic plate boundaries causes
earthquakes. The three types of stress are:
a._____________________________
b._____________________________
c. _____________________________
Questions
1. Seismology is the study of earthquakes.
2. A seismologist is a person who studies earthquakes.
3. Stress at tectonic plate boundaries causes
earthquakes. The three types of stress are:
a. compression
b. tension
c. shearing
Earthquakes cont.
4. Detecting earthquakes
a. Seismic waves – vibrations that
travel through the Earth
carrying the energy released
during an earthquake /
Earthquake waves.
b. Seismograph – instrument
that detects and measures
seismic waves
1. Primary Waves – P
waves
–
–
–
Push/pull waves (accordion
style)
Travel fastest
Travel through solids, liquids
and gases
Earthquakes cont.
•
2. Secondary Waves – S waves
– Arrive after P waves
– Waves vibrate or move side
to side and up and down
– Travels through solids only
3. Long or Surface Waves – L
waves
– Slowest moving
– Originate on the surface at
the epicenter
– Rolling or side to side
motion
– Travels through solids only
•
•
•
•
A highly simplified simulated recording
of earthquake waves (a seismogram)
can be seen to the left. Study this
sample seismogram and be sure you
can identify these parts:
P-waves and the P-wave arrival time
S-waves and the S-wave arrival time
S-P interval (expressed in seconds)
S-wave maximum amplitude
(measured in mm)
The seismogram below shows the arrival times of an earthquake’s
P -wave and S -wave recorded at a seismic station in Portland ,Oregon.
Questions
1. ________________________________ are vibrations that travel through
the Earth.
2. _____________________ waves (P-waves) have a
____________________________ motion.
3. S-waves, or __________________________ waves, arrive after the Pwaves, and move in a __________________________________ motion.
4. Long or ______________________ waves (L-waves) originate on the
surface and have a _________________________________ motion.
5. Fill in the chart by placing check marks in the appropriate boxes that show
through which states of matter each type of wave can travel:
solid liquid
P-waves
S-waves
L-waves
gas
Questions
1. Seismic waves are vibrations that travel through the Earth.
2. Primary waves (P-waves) have a push-pull motion.
3. S-waves, or secondary waves, arrive after the P-waves, and move in a side
to side and up and down motion.
4. Long or surface waves (L-waves) originate on the surface and have a rolling
or side to side motion.
5. Fill in the chart by placing check marks in the appropriate boxes that show
through which states of matter each type of wave can travel:
P-waves
S-waves
L-waves
solid liquid
x
x
x
x
gas
x
Earthquakes cont.
c. Focus – point beneath the
surface where the
earthquake begins.
d. Epicenter – point on the
surface where the
earthquake is located.
– Directly above the focus
– Energy of the seismic
wave is the greatest here
– The types of rock and soil
around the epicenter
affect how much the
ground shakes.
– Most violent shaking
occurs here
e. Earthquakes
occur along
fault lines at
the edges of
the tectonic
plates.
Questions
1.The __________________ is the point beneath
the surface of the earth where the earthquakes
originate.
2.The __________________ is the point on the
surface of the earth directly above the focus.
3.Earthquakes occur along
_____________________ lines on the edges of
____________________ plates.
Questions
1.The focus is the point beneath the surface of the
earth where the earthquakes originate.
2.The epicenter is the point on the surface of the
earth directly above the focus.
3.Earthquakes occur along fault lines on the edges
of tectonic plates.
Earthquakes cont.
Measuring Earthquakes
a. Magnitude – is a measurement of
earthquake strength based on seismic waves
and movement along faults.
b. Three ways of measuring earthquakes:
• 1.Richter Scale – a rating of the size of seismic
waves as measured by a mechanical or
electronic seismograph.
Earthquakes cont.
–
Provides accurate
measurements for small,
nearby earthquakes
– Less reliable for distance
or large quakes
2. Mercalli scale – rates
earthquakes according to
their intensity.
– Not a precise
measurement
– Describes how the
earthquake affects
people, buildings and the
land surface
Earthquakes cont.
–
Same quake can have
different ratings because
of different amounts of
damage at different
locations.
3. Moment Magnitude Scale –
estimates the total energy
released by an
earthquake.
– Rates all size
earthquakes, near and far
–
Example: a magnitude 6
earthquake compared to a
magnitude 5, releases 32
times as much energy as a 5
and nearly 1000 times as
much as a 4 earthquake.
•
The Richter scale
measures the energy
released in an
earthquake by measuring
the size of the seismic
waves.
• The Mercalli scale
measures the results of
an earthquake, such as
the shaking and damage
that people actually feel
and see.
Modified Mercalli Scale
Questions
1.What is magnitude?
2. What are the three ways of measuring
earthquakes?
a.
b.
c.
Questions
1.What is magnitude? A measurement of
earthquake strength based on seismic waves
and movement along faults.
2. What are the three ways of measuring
earthquakes?
a. The Richter Scale
b. Mercalli Scale
c. Moment Magnitude Scale
Earthquakes cont.
B. Earthquake Hazards and
Safety
1. How earthquakes cause
damage – the severe
shaking produced by seismic
waves can cause damage
near the epicenter or at great
distances.
a. Local soil conditions – the
thick, loose soil shakes more
violently than dense rock
b. Liquefaction- occurs when
an earthquake’s violent
shaking turns loose, soft soil
to mud which can sink
buildings, or cause landslides
Earthquakes cont.
c. Aftershocks – an
earthquake that occurs after
a larger earthquake in the
same area
d. Tsunamis – tidal wave
e. Indirect damage from fire
or flooding
2. Monitoring Faults –
earthquakes are very
unpredictable but certain P &
S wave patterns can be
monitored.
a. seismograph readings
Thursday, January 04, 2007 at 08:30:11 UTC
Earthquake Location
Major Tectonic Boundaries: Subduction Zones -purple, Ridges -red and Transform Faults -green
Description
Richter Magnitudes
Earthquake Effects
Frequency of Occurrence
Micro
Less than 2.0
Micro earthquakes, not felt.
About 8,000 per day
Very minor
2.0-2.9
Generally not felt, but recorded.
About 1,000 per day
Minor
3.0-3.9
Often felt, but rarely causes
damage.
49,000 per year (est.)
4.0-4.9
Noticeable shaking of indoor
items, rattling noises. Significant
damage unlikely. Much like a
passing truck
6,200 per year (est.)
Moderate
5.0-5.9
Can cause major damage to
poorly constructed buildings over
small regions. At most slight
damage to well-designed
buildings.
800 per year
Strong
6.0-6.9
Can be destructive in areas up to
about 100 miles across in
populated areas.
120 per year
Major
7.0-7.9
Can cause serious damage over
larger areas.
18 per year
Great
8.0-8.9
Can cause serious damage in
areas several hundred miles
across.
1 per year
Rarely, great
9.0 or greater
Devastating in areas several
thousand miles across.
1 per 20 years
Light
The Richter Scale
Magnitude
Effects
Estimated Number
Per Year
less than 2.5
Usually not felt, but can be recorded by
seismograph
900,000
2.5 to 5.4
Often felt but only causes minor damage
30,000
5.5 to 6.0
Slight damage to structures
500
6.1 to 6.9
May cause much damage in populated areas
100
7.0 to 7.9
Major earthquake; serious damage
20
8.0 or greater
Great earthquake; can totally destroy
communities near the epicenter
One every 5-10 years
Earthquakes cont.
b. satellite monitors
c. laser-ranging devices
d. creep meters – wire
stretched across a fault to
measure horizontal
ground movement
3. Making buildings safer
a. Location
b. Construction methods
–
Materials used
– Building codes
Earthquakes cont.
4. Safety
a. Drills
b. Take Precautions during
and after quake
c. Preparedness – earthquake
kit
Questions
1. What are three things that can cause damage after an earthquake?
a.
b.
c.
2. Two ways scientists can monitor earthquakes are:
a.
b.
3. What are two ways to make buildings safer in case of earthquakes?
a.
b.
4. What are two things people can do to be safer in case of earthquakes?
a.
b.
Questions
1. What are three things that can cause damage after an earthquake?
a. Loose soil, liquefaction, aftershocks, tsunamis, fires, flooding
b.
c.
2. Two ways scientists can monitor earthquakes are:
a. seismograph readings, satellite monitors, laser devices, creep meters
b.
3. What are two ways to make buildings safer in case of earthquakes?
a. location, materials used, building codes
b.
4. What are two things people can do to be safer in case of earthquakes?
a. safety drills, precautions during and after quake, earthquake kits
b.
II. Volcanoes
A. Volcano: a weak spot in the
earth’s crust where molten
material, or magma, comes to
the surface as lava.
1. Volcanology – study of
volcanoes
2. Volcanologist – geologist that
studies volcanoes
3. Volcanoes and Plate Tectonics
a. Most volcanoes occur along
divergent plate boundaries
such as the mid-ocean ridge,
or in subduction zones around
the edges of oceans.
Mt. Etna, Sicily (2002-03)
Volcanoes cont.
b. Magma – molten mixture of
rock-forming substances,
gases and water vapor from
the mantle. Occurs
underground.
c. Lava – when the magma
reaches the surface.
d. Hot spot – an area where
magma from deep within the
mantle melts through the
crust like a blow torch.
e. Hot spots in the ocean floor
create islands such as the
Hawaiian Islands
Volcanoes cont.
e. a volcano forms where magma
breaks through the earth’s
crust and lava flows to the
surface
Volcanic vent on the
Big Island, Hawaii
Questions
1. A volcano is a _______________________________ in the Earth’s
________________ where ________________________ comes through.
2. The study of volcanoes is called
____________________________________________.
3. What is the difference between magma and lava?
______________________________________________________________
______________________________________________________________
4. ________________________ are areas where magma melts through the
crust. This phenomenon created the __________________________________.
Questions
1. A volcano is a weak spot in the Earth’s crust where
magma comes through.
2. The study of volcanoes is called volcanology
3. What is the difference between magma and lava?
Magma is molten material below the earth’s surface;
lava is molten material on top of earth’s surface.
4. Hot spots are areas where magma melts through the
crust. This phenomenon created the Hawaiian Islands.
Volcanoes cont.
4. Volcanic Activity
a. Inside a Volcano
• Magma chamber – pocket of magma beneath the volcano
• Pipe – a long tube in the ground that connects the magma
chamber to the surface, magma flows through this tube
• Vent – opening where molten rock and gas leave the
volcano
Volcanoes cont.
b. Lava flow – the area
covered by lava as it
pours out a vent.
c. Crater – a bowl-shaped
area that may form at
the top of a volcano
around the volcano’s
central vent.
Questions
1. Diagram a volcano. Draw and label the following parts in the correct places:
magma chamber, vent, and crater.
Questions
1. Diagram a volcano. Draw and label the following parts in the correct places:
magma chamber, vent, and crater.
Volcanoes cont.
5. Types of Volcanic Eruptions – the silica
content of the magma influences how
the volcano erupts.
a. Quiet Eruption – magma flows easily.
Volcanoes cont.
• Gas dissolved in the magma
bubbles out gently
• Runny lava “oozes” quietly
from the vent
• Produces two kinds of lava
1. pahoehoe – slow-moving,
hot lava; cooled surface looks
like wrinkles , or coils of
hardened rock.
2. aa – faster-moving, cooler
lava; cooled surface forms
jagged lava chunks.
• Ex. Mount Kilauea
pahoehoe
Aa lava (14 cm x 12 cm). Kilauea,
Most Dangerous U.S. Volcanoes, in Descending Order
1. Kìlauea, Hawaii
2. Mount St. Helens, Washington State
3. Mount Rainier, Washington State
4. Mount Hood, Oregon
5. Mount Shasta, California
6. South Sister, Oregon
7. Lassen Volcanic Center, California
8. Mauna Loa, Hawaii
9. Redoubt Volcano, Alaska
10. Crater Lake area, Oregon
11. Mount Baker, Washington State
12. Glacier Peak, Washington State
13. Makushin Volcano, Alaska
14. Akutan Island, Alaska
15. Mount Spurr, Alaska
16. Long Valley caldera, California
17. Newberry Crater, Oregon
18. Augustine Island, Alaska
Only three of the most dangerous U.S. volcanoes are sufficiently monitored, according to the report:
Kìlauea in Hawaii, Mount St. Helens in Washington State, and the Long Valley caldera in California.
Volcanoes cont.
b. Explosive Eruptions – magma
does not flow but is blown
out the volcano.
•
Magma is thick and sticky
building up in the volcano’s
pipe, plugging it
•
Trapped gases build up
pressure until they explode
•
The explosion breaks the
lava into fragments that cool
quickly in different sizes.
1. volcanic ash
2. cinders
3. volcanic bomb
Volcanoes cont.
c. Pyroclastic Flow – occurs when
an explosive eruption hurls
out pyroclastic materials:
ash, cinders, bombs and
gases. Example – Mount St.
Helens
6. Stages of a Volcano
a. Active – a volcano that is
erupting or has shown signs
that it may erupt in the near
future. Ex. Mt. St. Helens
b. Dormant – a “sleeping”
volcano, may erupt in the
future. Ex. Mt. Hood
Hualalai volcano, on the west side of the island, is also
considered to be active. Its last eruption occurred in
1802.
Volcanoes cont.
• c. Extinct- a dead
volcano, unlikely to
erupt again. Ex.
Crater Lake
Volcanoes cont.
Mono Hot Springs
7. Other Types of Volcanic
Activity
a. hot spring – forms where
underground water heated by
a nearby body of magma
rises and collects in a natural
pool.
b. Geothermal energy –
energy source produced by
water heated in volcanic
areas and used for electricity.
Yellowstone National Park
Questions
1. The two types of volcanic eruptions are
______________________ and ______________________.
2. Pyroclastic flow consists of __________________,
____________________,__________________________, and
____________________.
3. Please complete the following chart:
Volcano Stage
Description
May erupt in the future.
Is unlikely to ever erupt again.
Is erupting or may erupt soon.
4. What are two other types of volcanic activity?
a.
b.
Questions
1. The two types of volcanic eruptions are quiet and explosive.
2. Pyroclastic flow consists of ash, cinder, volcanic bombs, and toxic
gases.
3. Please complete the following chart:
Volcano Stage
dormant
extinct
active
Description
May erupt in the future.
Is unlikely to ever erupt again.
Is erupting or may erupt soon.
4. What are two other types of volcanic activity?
a. hot springs
b. geothermal energy
Shield
Volcanoes cont.
Shield cone
B. Volcanic Landforms
1. Shield Volcanoes – thin layers
of lava pour out a vent and
harden on top of previous
layers.
– Quiet eruptions
– Wide, gently sloping
mountain
cinder
shield
– Ex. – Hawaiian Islands
2. Cinder Cone Volcanoes – thick
and stiff lava produce
pyroclastic material: ash,
cinder and bombs which pile
up around the vent.
Cinder cone
Volcanoes cont.
–
–
Explosive eruptions
Steep, cone-shaped
–
Ex. Mt. Paricutin in Mexico
C. Composite Volcanoes -lava
flows alternate with explosive
eruptions of pyroclastic
material: ash, cinder and
bombs.
– Quiet and Explosive
eruptions
– Tall, cone-shaped
– Layers of alternate ash
and lava
–
Ex. Mt. St. Helens , Mt. Fuji
Mount St. Helens in Washington State is an active
composite volcano, towering in a conelike shape
more than 8,000 feet (2,400 meters) above sea level.
USGS/Cascades Volcano Observatory
Quintessentially Japan ... Mt Fuji in the spring. Cherry season in Japan is a Barbara Cartland
fantasy of pink flowers and purple prose. Picture: Brian Johnston
Table Rock
Background:
Table Rock is a pint sized and remarkably symmetrical extinct volcanic cone, with a
summit elevation of 5621’. It stands roughly 1000’ higher than the surrounding desert in a setting
isolated from any nearby hills or peaks, which results in a unique and spectacular appearance. I
t’s classic and distinctive shape can be seen for many miles in any direction. This structure appears
to be a classic volcanic cone, but is actually a unique ‘maar’ cone created by the interaction between
groundwater and magma.
Volcanoes cont.
4. Lava Plateaus – high level
areas formed by layers of
lava.
5. Caldera – the hole left by the
collapse of a volcanic
mountain.
•
Example Crater Lake
caldera
Volcanic neck
That's a volcanic neck in the center, with a waterfall
Question
1. List and describe the three types of volcanoes:
a.
b.
c.
2. ________________________ are high, level areas
formed by layers of lava. A caldera is formed by the
___________________________ of a
___________________________ mountain.
Question
1. List and describe the three types of volcanoes:
a. Shield: made from thin layers of lava that build up
b. Cinder Cone: made from piled up pyroclastic materials
c. Composite: lava flows alternate with layers of
pyroclastic materials
2. Lava plateaus are high, level areas formed by layers of
lava. A caldera is formed by the collapse of a volcanic
mountain.
Volcanoes cont.
C. Landforms from Magma
1. Volcanic Neck – formed when
magma hardens in a
volcano’s pipe
2. Dike – magma forcing its way
across underground rock
layers and hardening
Shiprock, in New Mexico, also a volcanic neck.
Once again, the remainder of the volcano has eroded
away, leaving only the relatively hard rock that cooled
within the conduits feeding lava to the surface. In
addition to the vertical pipe at the center, a series of
dikes may be seen radiating away from the center.
These formed when lava entered fractures which formed
in the sides of the volcano
Volcanic Dike along Ross Maxwell Scenic Drive
Volcanoes cont.
3. Sill – magma squeezes
between rock layers and
hardens
4. Batholith – is a mass of rock
formed when a large body of
magma cools inside the crust
Below is a volcanic sill near Edinburgh, Scotland. Like a dike, a sill
forms when magma fills fracture in the rock, then cools in place.
A sill is largely horizontal, however, so it seems the magma
spreading out between the layers of sedimentary rock.
batholith
Volcanoes cont.
5. Dome Mountains – formed
when rising magma is blocked
by horizontal layers of rock,
forcing the layers of rock to
bend upward into a dome
shape. Eventually the rock
above the dome wears away
leaving the dome mountain
exposed.