Cops lock denser. the farther it is from the ridge axis, the lower the oceanic lithosphere sits on the asthenosphere and the deeper the water will be. this concept is known as the age versus depth relationship. (b) keeping in mind the age versus depth relationship, why is the belt of shallow sea wider over the east pacific rise than over the mid-atlantic ridge? exercise 2.9 subduction zones (a) based on island aro-trench geometry illustrated in figure 2.11, what factors determine the width of the arc-trench gap? explain. (c) based on your answer to (a), sketch two island arc-trench systems one with a wider arc-trench gap than the other narrow arc- trench gap wide arc-trench gap review the figure of profiles across four segments of the aleutian island arc page 42), which extends westward from mainland alaska. based on the positions of the volcanic arc and trench are indicated in each profile, answer the following questions (d) at what depth does meting apparently begin beneath the amchitka segment of the arc? explain your reasoning. (0 from these profiles four segments of the aleutian arc