Unit at a Glance
Chapter 8: Earthquakes
Standards
S6E5: Students will investigate the scientific view of how the earth’s surface is formed.
d. Recognize that lithospheric plates constantly move and cause major geological
events on the Earth's surface.
e. Explain the effects of physical processes (plate tectonics, erosion, deposition,
volcanic eruption, gravity) on geological features including oceans (composition,
currents, and tides).
Unit Vocabulary
Seismology: the study of earthquakes.
Seismic Waves: waves of energy generated during earthquakes that travel through the Earth.
Primary Waves: the fastest seismic waves; also known as p-waves.
Secondary Waves: the second fastest seismic waves; also known as s-waves.
Surface Waves: the slowest seismic waves that travel along the surface of the Earth.
Deformation: a change in the shape of rock due to stress caused by tectonic plate
movements.
Elastic Rebound: the sudden return of elastically deformed rock to its undeformed shape (the
*snap* back).
Seismograph: an instrument (machine) that records seismic waves during an earthquake.
Seismogram: the tracing of earthquake motion created by a seismograph machine.
Focus: the point inside the Earth where an earthquake begins.
Epicenter: the point on Earth’s surface directly above an earthquakes starting point (the focus).
Fault: a break in Earth’s crust along which portions of Earth’s crust move relative to one
another.
Normal Fault: a fault in which the hanging wall moves down relative to the footwall. Occurs at
divergent boundaries.
Divergent Boundary: where two tectonic plates separate or divide.
Reverse Fault: a fault in which the hanging wall moves up relative to the footwall. Occurs at
convergent boundaries.
Convergent Boundary: where two tectonic plates collide.
Strike-Slip Fault: a fault in which opposing forces cause rock to break and move horizontally.
Occurs at transform boundaries.
Unit at a Glance
Transform Boundary: where two tectonic plates slide past one another horizontally.
Gap Hypothesis: the theory that states that sections of active faults that have had few
earthquakes are likely to be the sites of strong earthquakes in the future.
Seismic Gap: Any area along a fault where few earthquakes have happened recently but
where strong earthquakes have happened before.
Essential Questions
1. Where do earthquakes take place and why do they occur?
2. What are the three different types of plate boundaries, their motions, and their faults?
3. What are the three different types of seismic waves and their characteristics?
4. How do scientists measure the strength and intensity of earthquakes?
5. How do scientists predict where earthquakes will occur and how strong they will be?