Chapter 11 Notes
Sec. I: Plate Tectonics
I. Earth’s Moving Plates
A. plates- large pieces of rock that make-up the lithosphere
B. plates move centimeters a year
C. Pangea- supercontinent made up of all continents fit together
II. Theory of Plate Tectonics
A. Plates are in constant , slow motion
B. plates form and move
C. plates interact, produce volcanoes, mountain ranges, earthquakes, and features
of the ocean floor
D. plates move due to movement of material in the upper mantle
III. Effects of Plate Movement
A. plate boundaries- cracks between the plates of the lithosphere
1. plates slide past each other
2. plates pull apart
3. plates move together
Sec. II: Earth’s Crust in Motion
I. Stress in the Crust
A. Earthquakes- the shaking and trembling results from the movement of
rock beneath Earth’s surface
B. Stress- a force that acts on rock to change its shape or volume; adds energy to
rock
II. Types of Stress
A. Shearing- stress that pushes a mass or rock in two opposite directions
B. Tension- stress force that pulls on the crust, stretching rock so that it becomes
thinner in the middle
C. compression- stress force that squeezes rock until it folds or breaks
D. Stress works over millions of years
E. deformation- any change in the volume or shape of Earth’s crust
III. Kinds of Faults
A. fault- a break in the curst where slabs of crust slip past each other
1. rocks on either side move up or down or sideways
2. occur along plate boundaries, where forces of plate motion compress,
pull, or shear the crust so much it breaks
B. Strike-slip Faults
1. rocks on either side of the fault slip past each other sideways with little
up or down motion
2. transform boundary- strike-slip fault that forms the boundary between 2
plates
3. San Andreas Fault (California)
C. Normal Faults
1. fault is at an angle, so one block of rock lies above the fault, while the
other block lies below the fault
2. hanging wall- half of the fault that lies above
3. footwall- half of the fault that lies below
4. Sandia Mountains, NM
D. Reverse Faults
1. produced by compression forces
2. same structure as a normal fault, but the blocks move in the opposite
direction
3. Appalachian Mountains
IV. Friction Along Faults
A. Friction- the force that opposes the motion of one surface as it moves across another surface
B. moderate friction, sides of the fault jam together, produce small earthquakes
C. high friction, rocks lock together and do not move, produce large earthquakes
D. earthquakes release the stress and plates slide past each other
V. Mountain Building and Uplift
A. Mountains formed by faulting
1. two plates move away from each other
2. tension forces create many normal faults
3. when two of these normal faults form parallel to each other, a block of
rock is left lying between them
4. as the hanging wall of each normal fault slips downward, the block in
between moves upward
5. When a block of rock lying between two normal faults slides
downward, a valley forms
B. Mountains Formed by Folding
1. plate movement causes the crust to fold
2. folds- bends in rock that form when compression shortens and thickens
part of earth’s crust
C. Anticlines and Synclines
1. anticline- a fold in rock that bends upward into an arch
2. syncline- a fold in rock that bends downward in the middle to form a
bowl
3. found where compression forces have folded the crust
4. Black Hills
D. Plateaus
1. uplift can raise plateaus
2. plateau- a large area of flat land elevated high above sea level
3. Colorado plateau
Sec. 3: Measuring Earthquakes
I. Earthquakes
A. focus- point beneath Earth’s surface where rock that is under stress breaks,
triggering and earthquake
B. epicenter- the point on the surface cirectly above the focus
II. Seismic Waves
A. Carry the energy of an earthquake away from the focus, through Earth’s
interior, and across the surface
B. Energy is greatest at the epicenter
C. Categories
1. P waves
a. comes from focus
b. earthquake waves that can compress and expand the ground like
an accordion
c. first waves to arrive
d. can move through both solids and liquids
2. S waves
a. occur after P waves
b. earthquake waves that vibrate from side to side as well as up and
down
c. shake the ground back and forth
d. can not move through liquid
3. surface waves
a. when p waves and s waves reach the surface, some are
transformed into surface waves
b. move more slowly than p & s waves
III. Seismograph
A. records and measures the vibrations of seismic waves
B. records the ground movements caused by seismic waves
IV. Measuring Earthquakes
A. Magnitude- a measurement of earthquake strength based on seismic waves and
movement along faults
B. Mercalli Scale- rates earthquakes according to their intensity
C. Richter Scale- rating of the size of seismic waves as measured by a particular
type of mechanical seismograph
D. Moment Magnitude Scale
1. rating system that estimates the total energy released by an earthquake
2. can be used to rate earthquakes of all sizes, near or far
V. Locating the Epicenter
A. scientists measure the difference between the arrival times of P & S waves to determine epicenter
B. Farther away an earthquake is, greater the time between arrival of P & S waves
Sec. 4: Volcanic Activity
I. How Magma Reaches Earth’s Surface
A. Magma rises because it is less dense than surrounding solid material
B. Volcanic Eruptions
1. gases are trapped in magma under pressure
2. as magma rises, pressure is released
3. volcano erupts when an opening develops in weak rock on the surface
4. gases dissolved in magma rush out, carrying magma with them
II. Inside a Volcano
A. Magma chamber- pocket where magma collects beneath a volcano
B. Pipe- a long tube in the ground that connects the magma chamber to Earth’s
surface
C. Vent- opening in a volcano through which molten rock and gas leave
D. Lava flow- area covered by lava as it pours out of a vent
E. Crater- a bowl-shaped area that may form at the top of a volcano around the
volcano’s central vent
III. Characteristics of Magma
A. Temperature- determines if it is thick of fluid (hotter=more fluid)
B. Silica
1. material that is formed from the elements oxygen and silicon
2. determines how easily magma flows (more silica= thicker magma)
3. more silica= lighter color
IV. Types of Volcanic Eruptions
A. Silica content of magma determines if volcanic eruption is quiet or explosive
B. Quiet eruptions
1. magma flows easily
2. Lava types
a. Pahoehoe- fast moving, hot
b. aa- cooler and slower moving
C. Explosive eruptions
1. magma is thick and sticky
2. slowly builds up in volcano’s pipe, like a cork
3. trapped gas builds up pressure until it explodes
4. pyroclastic flow- occurs when an explosive eruption hurls out ash,
cinders, and bombs as well as gases
V. Stages of a Volcano
A. active- live volcano is one that is erupting or has show signs that it mnay erupt
in the near future
B. dormant- sleeping volcano
C. extinct- dead volcano unlikely to erupt again
VI. Monitoring Volcanoes
A. monitor magnetic field
B. monitor water level in a volcano’s crater lake
C. monitor temp. of water near surface
D. monitor the many small earthquakes in area around volcano
VII. Other Volcanic Activity
A. Hot springs- groundwater heated by a nearby body of magma collects in a pool
B. Geysers- a fountain of water and steam that erupts from the ground
C. geothermal energy- reliable energy source provided by water heated by
magma
VIII. Volcano Hazards
A. Quiet eruption- lava flows pour from vents, setting fire to and burying everything in their path.
B. Explosive eruption- volcano belches out hot, burning clouds of volcanic gas, ash, cinders, and bombs
Section 5: Volcanic Landforms
I. Landforms from Magma
A. Volcanic necks- forms when magma hardens in a volcano’s pipe
B. dikes- magma that forces itself across rock layers & hardens
C. sills- forms when magma squeezes between layers of rock
D. batholiths- large rock masses formed when a large body of magma cools inside
the crust
E. dome mountains- forms when rising magma is blocked by horizontal layers of
rock
II. Landforms from Lava and Ash
A. Shield Volcanoes- thin layers of lava pour out of a vent and harden on top of
previous layers to build a wide, sloping mountain
B. Cinder Cone Volcanoes- a steep, cone-shaped hill or mountain
C. Composite volcanoes- tall, cone-shaped mountains in which layers of lava
alternate with layers of ash
D. Lava Plateaus- high, level areas formed from lava eruptions
E. Calderas- huge hole left by the collapse of a volcanic mountain
III. Soils from Lava and Ash
A. soil is initially barren
B. over time, soil forms
C. soil becomes fertile
Sec. I: Plate Tectonics
I. Earth’s Moving Plates
A. plates- large pieces of rock that make-up the lithosphere
B. plates move centimeters a year
C. Pangea- supercontinent made up of all continents fit together
II. Theory of Plate Tectonics
A. Plates are in constant , slow motion
B. plates form and move
C. plates interact, produce volcanoes, mountain ranges, earthquakes, and features
of the ocean floor
D. plates move due to movement of material in the upper mantle
III. Effects of Plate Movement
A. plate boundaries- cracks between the plates of the lithosphere
1. plates slide past each other
2. plates pull apart
3. plates move together
Sec. II: Earth’s Crust in Motion
I. Stress in the Crust
A. Earthquakes- the shaking and trembling results from the movement of
rock beneath Earth’s surface
B. Stress- a force that acts on rock to change its shape or volume; adds energy to
rock
II. Types of Stress
A. Shearing- stress that pushes a mass or rock in two opposite directions
B. Tension- stress force that pulls on the crust, stretching rock so that it becomes
thinner in the middle
C. compression- stress force that squeezes rock until it folds or breaks
D. Stress works over millions of years
E. deformation- any change in the volume or shape of Earth’s crust
III. Kinds of Faults
A. fault- a break in the curst where slabs of crust slip past each other
1. rocks on either side move up or down or sideways
2. occur along plate boundaries, where forces of plate motion compress,
pull, or shear the crust so much it breaks
B. Strike-slip Faults
1. rocks on either side of the fault slip past each other sideways with little
up or down motion
2. transform boundary- strike-slip fault that forms the boundary between 2
plates
3. San Andreas Fault (California)
C. Normal Faults
1. fault is at an angle, so one block of rock lies above the fault, while the
other block lies below the fault
2. hanging wall- half of the fault that lies above
3. footwall- half of the fault that lies below
4. Sandia Mountains, NM
D. Reverse Faults
1. produced by compression forces
2. same structure as a normal fault, but the blocks move in the opposite
direction
3. Appalachian Mountains
IV. Friction Along Faults
A. Friction- the force that opposes the motion of one surface as it moves across another surface
B. moderate friction, sides of the fault jam together, produce small earthquakes
C. high friction, rocks lock together and do not move, produce large earthquakes
D. earthquakes release the stress and plates slide past each other
V. Mountain Building and Uplift
A. Mountains formed by faulting
1. two plates move away from each other
2. tension forces create many normal faults
3. when two of these normal faults form parallel to each other, a block of
rock is left lying between them
4. as the hanging wall of each normal fault slips downward, the block in
between moves upward
5. When a block of rock lying between two normal faults slides
downward, a valley forms
B. Mountains Formed by Folding
1. plate movement causes the crust to fold
2. folds- bends in rock that form when compression shortens and thickens
part of earth’s crust
C. Anticlines and Synclines
1. anticline- a fold in rock that bends upward into an arch
2. syncline- a fold in rock that bends downward in the middle to form a
bowl
3. found where compression forces have folded the crust
4. Black Hills
D. Plateaus
1. uplift can raise plateaus
2. plateau- a large area of flat land elevated high above sea level
3. Colorado plateau
Sec. 3: Measuring Earthquakes
I. Earthquakes
A. focus- point beneath Earth’s surface where rock that is under stress breaks,
triggering and earthquake
B. epicenter- the point on the surface cirectly above the focus
II. Seismic Waves
A. Carry the energy of an earthquake away from the focus, through Earth’s
interior, and across the surface
B. Energy is greatest at the epicenter
C. Categories
1. P waves
a. comes from focus
b. earthquake waves that can compress and expand the ground like
an accordion
c. first waves to arrive
d. can move through both solids and liquids
2. S waves
a. occur after P waves
b. earthquake waves that vibrate from side to side as well as up and
down
c. shake the ground back and forth
d. can not move through liquid
3. surface waves
a. when p waves and s waves reach the surface, some are
transformed into surface waves
b. move more slowly than p & s waves
III. Seismograph
A. records and measures the vibrations of seismic waves
B. records the ground movements caused by seismic waves
IV. Measuring Earthquakes
A. Magnitude- a measurement of earthquake strength based on seismic waves and
movement along faults
B. Mercalli Scale- rates earthquakes according to their intensity
C. Richter Scale- rating of the size of seismic waves as measured by a particular
type of mechanical seismograph
D. Moment Magnitude Scale
1. rating system that estimates the total energy released by an earthquake
2. can be used to rate earthquakes of all sizes, near or far
V. Locating the Epicenter
A. scientists measure the difference between the arrival times of P & S waves to determine epicenter
B. Farther away an earthquake is, greater the time between arrival of P & S waves
Sec. 4: Volcanic Activity
I. How Magma Reaches Earth’s Surface
A. Magma rises because it is less dense than surrounding solid material
B. Volcanic Eruptions
1. gases are trapped in magma under pressure
2. as magma rises, pressure is released
3. volcano erupts when an opening develops in weak rock on the surface
4. gases dissolved in magma rush out, carrying magma with them
II. Inside a Volcano
A. Magma chamber- pocket where magma collects beneath a volcano
B. Pipe- a long tube in the ground that connects the magma chamber to Earth’s
surface
C. Vent- opening in a volcano through which molten rock and gas leave
D. Lava flow- area covered by lava as it pours out of a vent
E. Crater- a bowl-shaped area that may form at the top of a volcano around the
volcano’s central vent
III. Characteristics of Magma
A. Temperature- determines if it is thick of fluid (hotter=more fluid)
B. Silica
1. material that is formed from the elements oxygen and silicon
2. determines how easily magma flows (more silica= thicker magma)
3. more silica= lighter color
IV. Types of Volcanic Eruptions
A. Silica content of magma determines if volcanic eruption is quiet or explosive
B. Quiet eruptions
1. magma flows easily
2. Lava types
a. Pahoehoe- fast moving, hot
b. aa- cooler and slower moving
C. Explosive eruptions
1. magma is thick and sticky
2. slowly builds up in volcano’s pipe, like a cork
3. trapped gas builds up pressure until it explodes
4. pyroclastic flow- occurs when an explosive eruption hurls out ash,
cinders, and bombs as well as gases
V. Stages of a Volcano
A. active- live volcano is one that is erupting or has show signs that it mnay erupt
in the near future
B. dormant- sleeping volcano
C. extinct- dead volcano unlikely to erupt again
VI. Monitoring Volcanoes
A. monitor magnetic field
B. monitor water level in a volcano’s crater lake
C. monitor temp. of water near surface
D. monitor the many small earthquakes in area around volcano
VII. Other Volcanic Activity
A. Hot springs- groundwater heated by a nearby body of magma collects in a pool
B. Geysers- a fountain of water and steam that erupts from the ground
C. geothermal energy- reliable energy source provided by water heated by
magma
VIII. Volcano Hazards
A. Quiet eruption- lava flows pour from vents, setting fire to and burying everything in their path.
B. Explosive eruption- volcano belches out hot, burning clouds of volcanic gas, ash, cinders, and bombs
Section 5: Volcanic Landforms
I. Landforms from Magma
A. Volcanic necks- forms when magma hardens in a volcano’s pipe
B. dikes- magma that forces itself across rock layers & hardens
C. sills- forms when magma squeezes between layers of rock
D. batholiths- large rock masses formed when a large body of magma cools inside
the crust
E. dome mountains- forms when rising magma is blocked by horizontal layers of
rock
II. Landforms from Lava and Ash
A. Shield Volcanoes- thin layers of lava pour out of a vent and harden on top of
previous layers to build a wide, sloping mountain
B. Cinder Cone Volcanoes- a steep, cone-shaped hill or mountain
C. Composite volcanoes- tall, cone-shaped mountains in which layers of lava
alternate with layers of ash
D. Lava Plateaus- high, level areas formed from lava eruptions
E. Calderas- huge hole left by the collapse of a volcanic mountain
III. Soils from Lava and Ash
A. soil is initially barren
B. over time, soil forms
C. soil becomes fertile
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