Primary waves travel ____ as fast as secondary waves. a. half ...

[joe]

Primary waves travel ____ as fast as secondary waves.
  a. half
  b. twice
  c. three times
  d. at the same speed

Question 2

What prevents the subduction of terranes?
  a. The relative thin layer of crusts
  b. The low density
  c. The proximity from plate boundaries
  d. The compression of continental crust

[eliasc0401]

Answer to Question 1

ANS: B
Although the primary and secondary waves are generated at the same time, primary waves move faster
than the secondary waves. Their behavior through the Earth's interior affects their speed. Information
can be found in the section The Study of Earthquakes Provides Evidence of Layering.

Answer to Question 2

ANS: B
The thickness and low density of the terranes prevent subduction. Terranes are ancient island arcs and
parts of continental crust that are squeezed and sheared off onto the face of a continent. Information
can be found in the section Contemporary Oceanography Makes Use of Modern Technology.

[joe]

Great answer, keep it coming

[sultansheikh]

Excellent