whole arc, sometimes in questioning quotes, by some sort of analogy, perhaps because the zone once was or could be a convergent subductive plate border. The basis of the analogy is the Hellenic arc, the raised border. It could not have been raised all the way around without a subduction zone all the way around. The search for data revealing possible reasons for the asymmetry is an area of active research. If the problem is in part a matter of definition of terms, then the answer as far as it goes is a matter of redefinition. One redefinition distinguishes the Hellenic Trench from the Hellenic Trough, or Hellenic Subduction Trough. The Trench is only the foredeep of the Hellenic arc on the west side. It is possibly the location of the line of subduction, but the subduction begins with the first flexure of the African Plate downward (deformation front), which at least one source places at the Libyan continental margin. The Mediterranean Ridge is in this theory an accretionary complex associated with the subduction; that is, a collection of loose material left over from previous subduction. The term “subduction zone” also includes the slab of the overridden Wadati–Benioff zone. These definitions appear to solve the contradiction of the Hellenic Trench not going far enough around the arc to account for the eastern side. The Trough and the zone go all the way around. Subduction zone geometry Hellenic Arc amphitheater The Hellenic Arc seen on a map or in high-altitude photographs appears to be, if not actually is, an amphitheater, at least a bilaterally symmetrical arc about a N-S axis, with vertex on Crete, opening to the north. The wings of the arc are somewhat flatter than the vertex. The radius has been calculated at , which places the center at about , in the middle of the north Aegean Sea. The parallel trend of the volcanic arc at a radius of seems to give some approximate verification. One might suppose at first glance that some anomalous curvature of the African Plate had surrounded the Aegean Sea and was compressing it inward toward a point in the north Aegean, and that one might expect a mountain range to arise there. The western side of the trench has the appropriate faulting, a destructive convergent border in a reverse fault with a dip under the Hellenic Arc perpendicular to the strike. Further investigation