Unit 2:  Earthquakes and Earth's Interior

Big Idea:  A model of the structure and dynamics of Earth's interior where the transfer of heat 
                     from the interior towards the surface causes slow movement of Earth's tectonic 
                     plates is based largely on recordings of seismic waves.
Learning Targets:

  • I can describe natural processes in which heat transfer in the Earth occurs by conduction, convection, and radiation.
  • I can describe the interior of the Earth (in terms of crust, mantle, and inner and outer core) and where the magnetic field of the Earth is generated.
  • I can explain how scientists infer that the Earth has internal layers with discernable properties using patterns of primary (P) and secondary (S) seismic wave arrivals.
  • I can describe the differences between oceanic and continental crust (including density, age, composition).
  • I can explain the uncertainties associated with models of the interior of the Earth and how these models are validated.
  • I can describe how the sizes of earthquakes and volcanoes are measured or characterized.
  • I can describe the effect of earthquakes and volcanic eruptions on humans.
  • I can explain why fences are offset after an earthquake using the elastic rebound theory.

Bill Nye: Inside Our Planet

This video segment examines Earth's inner and outer cores.

E2.2A - I can describe the interior of the Earth (in terms of crust, mantle, and inner and outer cores) and where the magnetic field of the Earth is generated.

Greatest Discoveries with Bill Nye: Earth Science Science Channel,  2005 . Full Video.
Discovery Education. Web. 29 September 2014. <http://www.discoveryeducation.com/>.

Unit 2 Notes: Earthquakes and Earth's Interior
Exploring Inside Earth
E3.2b & E3.2d

These notes describe how scientists use models and seismic wave arrivals to help determine the layers of the Earth.
unit_2_notes_-_exploring_earths_interior.pdf
File Size: 39 kb
File Type: pdf
Download File

Kahn Academy:  Seismic Waves

This video explains P-waves and S-waves.

P waves are also know as primary waves.  These are the first ones to arrive.  P waves are seismic waves that compress and expand the ground like and accordion.  P waves can travel through both solids and liquids.

S waves are seismic waves, also known as secondary waves, that vibrate from side to side as well as up and down.  These shake the ground back and forth.  S waves cannot move through liquids.

Kahn Academy:  

The amount of time that it takes for a seismic wave to pass through the earth is dependent on the material that it encounters along its path.

By monitoring arrival times of seismic waves throughout the earth we can make determinations about what types of materials are found in the earth.

For example, S waves do not reach from an earthquake to the opposite side of the earth--indicates presence of a liquid core.

When traveling through the earth, seismic waves frequently pass through materials that transmit them more or less quickly. Remember that the speed of seismic waves depends on variations in strength and density of the rocks that they pass through.
Refraction: When seismic waves pass through different types of materials their speed is altered and consequently their path through the materials may be bent.

Kahn Academy:

The Mohorovicic Discontinuity, or "Moho", is the boundary between the crust and the mantle. The red line in the drawing at right shows its location. 

In geology the word "discontinuity" is used for a surface at which seismic waves change velocity. One of these surfaces exists at an average depth of 8 kilometers beneath the ocean basin and at an average depth of about 32 kilometers beneath the continents. At this discontinuity, seismic waves accelerate. This surface is known as the Mohorovicic Discontinuity or often simply referred to as the "Moho". 

Kahn Academy:

Scientists infer Earth's inner structure by recording and studying how seismic waves travel through Earth.

Kahn Academy:

The three main layers of the Earth are the crust,the mantle, and the core.  These layers vary greatly in size, composition, temperature, and pressure.

Check out these iPad apps...

Earthquakes:
Folds and Faults - Folds and Faults provides an illustrated overview of two significant topics in geology: folds and faults. Understanding folds and faults helps to explain how mountains form, how layers of rock change shape over time, and the underlying cause of earthquakes.  $0.99
Focus on Earthquakes - Focus on Earthquakes provides a comprehensive description of the causes and consequences of earthquakes. In addition to the text, this new-media textbook provides illustrations, photos, narrated animations and slide shows that aid in understanding the concepts presented. Interactive quizzes and review questions are provided throughout the text to test and reinforce one's understanding.  $3.99
Disaster Alert - Disaster Alert (by Pacific Disaster Center) provides a listing and an interactive map of Active Hazards occurring around the globe. Additional hazard information can be viewed and shared.  Free