Download Name: ___________________________ Chapter 6 Notes: Earthquakes Stress 

Forces in Earth’s Crust
Name: ___________________________
Chapter 6 Notes: Earthquakes
 Stress
 Stress: A force that acts on rocks to _______________ its shape or volume.
 Stress _______________ , pulls, or _______________ the rock in Earth’s crust
 Types of Stress
 Tension: a force that _______________ on the crust.
 It stretches the rock so it is _______________ in the middle.
 Occurs at _______________ Plate Boundaries
 Compression: the stress force that _______________ rock until it folds or breaks
 Occurs at _______________ Plate Boundaries
 Landforms from Compression
 _______________
 Shearing: a stress that _______________ rock in opposite directions
 Occurs at _______________ Plate Boundaries
 Landforms from tension
 _______________
 Faults
 Fault: is a break in the rock of the _______________ where rock surfaces slip past
each other.
 Faults occurs along plate _______________ where forces of the plate motion push
or pull the crust so much that the crust breaks.
 Hanging wall: block of rock that lies _______________ the fault.
 Footwall: rock that lies _______________ the fault.
 Types of Faults
 Normal Faults: fault in which the hanging wall has moved
_______________ relative to the footwall
 Occur where plates _______________
 Ex: Along the Rio Grande (rift valley)
 Reverse Faults: Faults in which the hanging wall moves
_______________ relative to the footwall

_______________ of normal fault

Occurs where plates _______________
 Ex: in Canada & Northern Rocky Mtns
 Strike-Slip Fault: fault in which the rocks slide
_______________ each other without up and down motion
 Occurs at _______________ boundaries
 Changing Earth’s Surface
 The forces of plate movement have added ________ , anticlines, synclines, and plateaus.

Folded Mountains: plate movement and _______________
of crust cause Earth’s crust to fold
 Anticline: the fold in the rock that bends ___________

Syncline: the fold in the rock that bends ____________
 Examples of Folded Mountains
 _______________ Appalachian Mountains
 Himalayas in _______________
 _______________ in Switzerland

Fault Block Mountains: forms when 2 _______________
Faults cut through a block of rock

Plateau: large area of flat land _________ high above sea level
 Formed when forces uplift some areas _______________ much folding
Earthquakes and Seismic Waves:
 Earthquake
 Earthquake: shaking and _______________ that results from the movement of rock
_______________ earth’s surface
 Caused by _______________ of plate movement.
 The movement causes _______________ in the crust
 At the fault
 Stress _______________ until the rock breaks
 _______________ an enormous amount of energy

Focus: the area ___________ Earth’s surface where rock is under stress and breaks.
 Triggers an _______________
 Usually about 100 km _______________ the surface
 Epicenter: The point on Earth’s surface directly _______________ the focus.
 Seismic Waves
 Seismic Waves: vibrations that travel through Earth _______________ the energy
released during an earthquake
 Types of Seismic waves
 P waves: the __________ wave to arrive
 _______________ waves
 They _______________ and expand
 Like an accordion

S



waves: come _______________ the P waves
_______________ waves
Vibrate ___________ to side and up and down
Cannot move through _______________

Surface Waves: P waves and S waves that reach the _______________
 They move ________ but still cause severe ground movement because it has
_______ soil, sand, gravel, mud, and small rocks that can move, _______ and slide.
Measuring Earthquakes
 Scientists use 3 main methods to _______________ Earthquakes
 Mercalli Scale: rates earthquakes according to _______________
 The same earthquake can have _______________ Mercalli ratings
 Different amounts of ground _______________ at different places
 Richter Scale: rates earthquakes according to the _______________ of the seismic waves.
 Magnitude: is the _________ assigned to the earthquake based on the ___________
 The magnitude tells how much _______________ was released by an earthquake.
 Moment Magnitude Scale: rating that estimates the _________ released by an earthquake.
 Scientists study _______________
 Seismograph: instrument that _______________ and measures seismic waves
 These show the ____________ of waves present and how __________ they were.
 Comparing Magnitude
 For each point increased in magnitude, 32 times as much _______________ is released
 Earthquakes below a 3 are barely _______________ .
 Magnitudes between 5-6 causes _______________ damage.
 Magnitude 8 or greater causes _______________ damage.
 Locating the Epicenter
 Geologists use the seismic waves to _______________ an earthquake’s epicenter
Monitoring Earthquakes
 Geologists us seismograph
 Seismogram: the pattern of zigzag lines on paper as a _______________ of an earthquake’s
seismic waves
 Instruments used to monitor faults
 _______________
 Creep Meters
 _______________ -Ranging Devices
 GPS _______________
Earthquake Safety
 _______________ from Earthquakes
 Shaking
 Can cause _______________ and avalanches
 Damage or destroy _______________ , bridges, utilities, pipes
 S-waves and Surface waves can _______________ buildings apart
 Loose soil shakes _______________ than solid rock
 Liquefaction
 Liquefaction: the result of the Earth’s shaking that turns _______________ to
liquid _______________ .
 Aftershocks
 Aftershock: an earthquake that occurs _______________ a larger earthquake in
the same area.
 May strike hours, _______________ , or months later
 Tsunamis
 Waves produced from earthquake under _______________
 Steps to Safety
 Drop, cover & hold

Indoors:
 Go under _______________ table or inside corner
 Avoid windows, _______________ , wall hangings, furniture

Outdoors:
 Go to _______________ area
 Avoid vehicles, power lines, trees, _______________