Download Volcanoes and Earthquakes

Volcanoes and Earthquakes
For two-column notes, underlined titles are main ideas
Volcanoes
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Volcanoes
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A mountain that forms in the Earth’s crust when
magma (molten material) reaches the surface and
cools to form solid rock.
When magma reaches the surface, it is called lava
Where volcanoes form
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At plate boundaries
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At divergent plate boundaries
At convergent plate boundaries
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where a continental and an oceanic
plate meet and the latter is subducted
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Example: Ring of Fire: a belt of volcanoes
along the edges of the Pacific plate
where two oceanic plate meet
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These often form island arcs, a string of islands
Examples: Japan, New Zealand, Caribbean
islands
Where volcanoes form
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Where volcanoes form
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At hot spots
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Places where material from the mantle rises
through the crust and melts to form magma
Hot spots stay in the same place while a plate
moves above them
– Example: The Hawaiian islands formed from a
hot spot under the Pacific plate
– Example: Yellowstone National Park is under a
hot spot in the state of Wyoming
Inside a volcano
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Inside a volcano
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Magma chamber
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Pocket where magma collects
Pipe
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Tube that extends from magma chamber to
top of volcano
Vent
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Opening in volcano (central vent on top;
may be several on sides)
Inside a volcano
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Inside a volcano
– Lava flow
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Spread of lava as it pours from vent
– Crater
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Bowl-shaped area that may form around
central vent
Inside a volcano
Draw this and label the diagram
Classwork 1
1.
2.
3.
4.
5.
6.
At what types of plate boundaries do volcanoes
form?
What is the difference between magma and lava?
What is a hot spot?
What is a magma chamber
What is a vent?
What is a pipe?
Volcanic eruptions
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Dissolved gases in magma expand, forcing
magma to flow through pipe and out vent
Eruption factors
– Silica is a mineral composed of the elements
oxygen and silicon and is found in magma
– Temperature determines whether lava is
thick or thin
Types of Eruptions
– Quiet Eruptions
– Explosive Eruptions
Volcanic eruptions
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Quiet eruptions - hazards
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Lava sets fire to or buries everything in its
path
Explosive eruptions - hazards
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Pyroclastic flow of hot gases, volcanic ash,
cinders and bombs can move quickly down
the sides of the volcano
Landslides of mud, melted snow and rock can
occur
Volcanic ash can be thrown high into the
atmosphere, where it can damage jet plane
engines
Volcanic activity
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Volcanic Activity
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Active
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Dormant
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Erupting or shows signs that it may erupt in
near future
“Sleeping” volcano expect to erupt again one
day
Extinct
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Unlikely to ever erupt again
Volcanic landforms
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From Ash and Lava
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Types of landforms
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Shield volcano – gently sloping lava flows
Cinder cone volcano – from explosive eruptions
Composite volcano – alternating layers of lava and
layers of ash, cinders, bombs
Lava plateau – Forms from repeated lava flows along
long cracks in an area
Caldera – hole left if magma chamber collapses after
eruption
Volcanic landforms – Ash and lava
Lava plateau
Volcanic landforms
How a caldera forms
Volcanic landforms
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From Magma
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Types of landforms
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Volcanic necks – Magma hardened in pipe, softer rock
around pipe eroded
Dikes and sills – Across rock layers, dike; between
rock layers, sill
Dome mountains – uplift pushes a hardened mass of
magma toward the surface
Batholith – Large body of magma forms inside crust
Volcanic landforms
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From Magma
Batholith
Classwork 2
1.
2.
3.
4.
5.
What are the two types of volcanic
eruptions?
What are the three types of volcanic
activity?
Describe the three types of volcano
How does a lava plateau form?
How does a caldera form?
Earthquakes
Forces in Earth’s Crust
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Stress
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Tension
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Compression
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Force that pulls crust and thins rocks in the
middle
Force that squeezes rocks until they fold or
break
Shearing
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Force that pushes mass of rock in two
opposite directions
Earthquakes
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Stress
Draw these
three types
of stress
Earthquakes
Forces in Earth’s Crust
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Faults
A fault occurs when enough stress builds up in
rock to break it
– Types of faults
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Normal
– Fault cuts through rock at an angle
– One block of rock sits over fault (hanging wall)
– Other block sits under the fault (footwall)
– During movement, hanging wall move
downward, footwall moves upward
Forces in Earth’s Crust
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Faults
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Types of faults
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Reverse
– Same structure as normal fault
– During movement, hanging wall moves
upward, footwall moves downward
Strike-Slip Faults
– Rocks on either side of fault slip past each
other
– Little up or down motion
Forces in Earth’s Crust
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Faults
Draw this
normal
fault and
label the
footwall
and
hanging
wall
Forces in Earth’s Crust
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Faults
Draw this
reverse
fault and
label the
footwall
and hanging
wall
Earthquakes
Forces in Earth’s Crust
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Faults
Draw
this
strikeslip fault
Forces in Earth’s Crust
Creating new landforms
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Folding Earth’s crust by compression
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Anticlines
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Fold that bends upward into an arch
Synclines
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Fold that bends downward like a V
Folded mountains
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Himalayan mountains in Asia
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Alps in Europe
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Process requires millions of years
Forces in Earth’s Crust
Creating new landforms
Draw this
diagram,
label the
syncline and
anticline and
draw in the
arrows
showing the
direction of
force
Forces in Earth’s Crust
Creating new landforms
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Stretching Earth’s Crust
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Fault block mountains
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Two normal faults cause valleys to drop down
on either side of a block of rock
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As hanging walls of each fault drop down, block
in between stands above surrounding valleys
Forces in Earth’s Crust
Creating new landforms
Draw this
diagram
Forces in Earth’s Crust
Creating new landforms
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Uplifting Earth’s Crust
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Plateaus
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Large area of land elevated high above sea level
Classwork 3
1.
2.
3.
4.
5.
Describe the three types of stress
What is a fault?
Describe the three types of faults
Describe three types of folds in the Earth’s
crust
How is a plateau formed?
Earthquakes
Earthquakes and Seismic Waves
Seismic Waves
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Waves produced by earthquakes that travel
through the Earth
Earthquakes
Types of Seismic Waves
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P Waves
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Seismic waves that compress and expand ground
like an accordion (longitudinal)
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Fastest waves of the three
S Waves
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Seismic waves that can vibrate side-to-side or up
and down (transverse)
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Arrive after P waves
Surface Waves
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Similar to waves in water; can make ground roll
like ocean waves (also transverse)
Earthquakes
Earthquakes and Seismic Waves
Draw and label these
P, S and surface wave
diagrams
Anatomy of an earthquake
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An earthquake is the shaking and trembling
that results from movement of rock beneath
the surface
The point beneath Earth’s surface where
rock breaks under stress and
triggers an earthquake is called the focus
The point on Earth’s surface directly above
the focus is called the epicenter
Measuring earthquakes
Monitoring Earthquakes
How do seismographs work?
Measuring earthquakes
Monitoring Earthquakes
Reading a Seismogram
Measuring earthquakes
Earthquakes and Seismic Waves
How is an epicenter located
Measuring earthquakes
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Modified Mercalli Scale
Rates the amount of shaking from an
earthquake
– Done by observation (no instruments)
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Richter Scale
Measures earthquake magnitude (size)
– Measure small earthquakes using
seismographs
– Take distance into account
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Moment Magnitude Scale
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Measure total energy of an earthquake using
seismographs
Measuring earthquakes
Earthquakes and Seismic Waves
How are earthquakes measured
Moment Magnitude Scale
Modified Mercalli Scale
Measuring earthquakes
Monitoring Earthquakes
Earthquake risk in the United States
Earthquake Hazards
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Ground Shaking
– Buildings can be damaged by the shaking
– Buildings can be damaged by subsidence (the
ground beneath them settling to a different
level
– Soil liquefaction (mixing of sand or soil and
groundwater) causes ground becomes very
soft and acts similar to quicksand. Ground Displacement
– Land on sides of fault moves in different
directions
Earthquake Hazards
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Flooding
– Dams or levees break
– Tsunamis (huge wave caused by an
earthquake under the ocean) 2004 Indian
Ocean tsunami killed over 230000 people
– Seiches (occur on lakes shaken by
earthquakes)
Fires
– Broken gas lines and power lines
– Tipped over wood or coal stoves.
Earthquake risk in the world
Pacific Ring of Fire
Mid-Ocean Ridge
Eurasian-Melanesian
Where Earthquakes Occur
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Most Earthquakes occur on plate boundaries
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There are three zones:
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Some earthquakes can occur on plate boundaries that
aren’t active anymore (like in Missouri, US or in central
China)
Pacific Ring of Fire (mostly subduction but some transform
plate boundaries)
Mid-Ocean Ridges (diverging ocean plates)
Eurasian-Melanesian (continental plates colliding)
If there are several faults in an area they can form an
interconnected fault zone
Classwork 4
1.
2.
3.
4.
5.
How does a seismograph work
How do you read a seismogram?
What is the risk of an earthquake in Florida?
What part of the United States has the highest
earthquake risk?
Where do most earthquakes occur?