Week 4


  1. Figure 2 shows a large lateral velocity variation in the upper mantle. The author suggests that these differences could be a reflection of the temperature variation within the asthenosphere. Could there be other factors that contribute to the velocity variation within the Asthenosphere ?

  2. The article suggests that western North America (e.g., from the Canadian shield to the Pacific plate margin) contains the largest mantle-velocity gradient on Earth. If this is true, what do you think causes this phenomenon ?

  3. What do you think is the origin of the high velocity lower crustal layer?

  4. Why authors selected North America for such study?

  5. How the Proterozoic lithosphere of Colorado and New Mexico differs from lithosphere beneath the Archean core of the continent?

  6. How Moho layer formed at Rocky Mountains as per the authors' point of view?

  7. What does the combined geophysical and geologic data from the CD-ROM experiment provide?

  8. What does the integrated data set for the Cheyenne belt, the Farwell-Lester Mountain zone, and the Jemez lineament, and their corresponding velocity anomalies in the mantle (to >200 km) indicate?

  9. What are the two provocative and testable hypotheses concerning lithospheric evolution?

Questions or Comments?
Dr. Ali O. Oncel