1. The problem statement, all variables and given/known data (Picture is attached) a. Based on island arc-trench geometry in Fig 2.17, what factors determine the width of the arc-trench gap, and explain your answer? 2. Relevant equations None 3. The attempt at a solution 1. I think it is the subducting plate and the melting that occurs above the plate that determines the width of the gap, and that the accretionary wedge and the fore-arc basin are just part of the gap. However I honestly don't know and would really like help!