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Forces in Earth ’ s Crust . Earthquakes. What is stress?. A force that acts on rock to change its shape or volume. What are the three types of stress acting on rocks?. Tension Compression Shearing. - Forces in Earth ’ s Crust. Types of Stress: Tension.

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Presentation Transcript
what is stress
What is stress?
  • A force that acts on rock to change its shape or volume.
types of stress tension

- Forces in Earth’s Crust

Types of Stress: Tension

The stress force called tension pulls on the crust, stretching rock so that it becomes thinner in the middle.

types of stress compression

- Forces in Earth’s Crust

Types of Stress: Compression

The stress force called compression squeezes rock until it folds or breaks.

types of stress shearing

- Forces in Earth’s Crust

Types of Stress: Shearing

Stress that pushes a mass of rock in two opposite directions is called shearing.

what is the difference between an anticline and a syncline

- Forces in Earth’s Crust

What is the difference between an anticline and a syncline?

Over millions of years, the forces of plate movement can change a flat plain into landforms such as anticlines (fold that bends upward) and synclines (folds that bend downward), folded mountains, fault-block mountains, and plateaus.

Appalachian Mtns.

what causes these changes
What causes these changes?
  • The slow shift of Earth’s plates cause these changes.
what is a fault
What is a fault?
  • It is a break in the rock of the crust.
why do faults occur along plate boundaries
Why do faults occur along plate boundaries?
  • The forces of plate motion push or pull the crust so much that the rocks break.
  • Pull apart = Divergent Boundary = Tension Forces
  • Push together = Convergent Boundary = Compression Forces
  • Slide past = Transform Boundary = Shearing Forces
what is the difference between a hanging wall and a footwall
What is the difference between a hanging wall and a footwall?
  • Hanging wall – above the fault line
  • Footwall – below the fault line
slide18

- Forces in Earth’s Crust

Tension in Earth’s crust pulls rock apart, causing normal faults.

building vocab
Building Vocab
  • Shearing = stress that pushes a mass of rock in 2 opposite directions
  • Hanging wall = the block of rock that lies above a fault
  • Syncline = a fold in rock that bends downward to form a valley; youngest rock as center
  • Footwall = the block of rock that lies below the fault
  • Stress = a force that acts on rocks to change its shape or volume
  • Anticline = a fold in rock that bends upward in an arch; oldest rock as center
  • Plateau = a large area of flat land elevated high above sea level; Grand Canyon
earthquakes and seismic waves
Earthquakes and Seismic Waves
  • The point at which a rock under stress breaks and triggers an earthquake is called the focus.
  • The point on the surface directly above the focus is called the epicenter.
what are seismic waves
What are seismic waves?
  • Seismic waves are vibrations that travel through Earth carrying the energy released during an earthquake.
earthquakes and seismic waves1
Earthquakes and Seismic Waves

True or False?

The categories of seismic waves are:

(A.) P-wave

(B.) S-wave

(C.) Surface wave

Surface waves move more quickly than P waves and S waves.

False!

  • Seismic waves carry the energy of an earthquake away from the focus in all directions.
  • True!
slide28

Type of Wave Effect

  • P wave a. Shakes buildings from side to side
  • S wave b. Shakes buildings violently
  • Surface wave c. Causes buildings to contract and expand
  • A device that records the ground movements caused by seismic waves is a seismograph.
measuring earthquakes
Measuring Earthquakes
  • Mercalli Scale – damage
  • Richter Scale – magnitude/ size of seismic waves
  • Moment Magnitude Scale – amount of energy released
locating the epicenter
Locating the Epicenter

True or False?

  • The closer an earthquake, the greater the time between the arrival of P waves and S waves.
  • False!
  • The center of each circle represents a
  • Seismograph Station
  • The radius of each circle represents the
  • distance to the epicenter