Teaching with the EarthChem Geochemical Database Integrating
Research and Education > EarthChem > NAVDAT animations > Study
questions  Study questions  The following study questions are
arranged in chronological order. Use the slider and pause button
on the NAVDAT animation to examine in more detail the volcanic
activity which occurred during the time periods listed below. If
you prefer a printout of the full set of study questions, choose
Print from the File menu.      65-25 Ma    1. During this
period, what type of plate boundary was located along the
western margin of North America? Which plates were in contact at
this boundary, and in what direction was the subducting plate
moving relative to the upper plate? (to answer these questions,
see Tanya Atwater's animation)   2. subduction zone
Continental-margin subduction zone     Image courtesy of the
USGS.     In your introductory geology course, you learned that
a common feature found on the upper plate of a subduction zone
is a linear chain of volcanoe