Problem: In this location, the ocean plate to the west is subducting under the continental plate to the east. Comparing the diagram of a subduction zone below to the profile with earthquake locations that you just plotted, draw in the following features from the diagram onto your plot: Label the trench (zero on the x-axis) with an arrow pointing down and the word "trench". Draw a line on the cross section to show the subducting plate as it descends from the surface down into the earth. Draw arrows on the subducting and overriding plates to show their movement directions (on the diagram below, these are the fat gray arrows). Circle the zone of melting. At what depth (below the surface) and distance (horizontally, from the trench) does the magma that produces the volcanoes probably originate, and why? The crust-mantle boundary (aka "Moho" or Mohorovicic discontinuity) is about 10 km deep under oceanic crust and 50 km deep under continental crust. Draw a straight horizontal line at the depth of the Moho below the oceanic crust (from the left side of the profile to the trench), and another at the depth of the Moho below the continental crust (from the right side of the profile to the trench).