Von Huene et al.  outline a plan to study convergent margin processes in the Middle America Trench area. They describe the area as mainly an “erosional convergent margin,” which they represent as a fundamental feature of the circum-Pacific. The concept of tectonic erosion at this type of hypothetical margin has been reviewed by von Huene and Scholl . They portray tectonic erosion (or “subduction erosion”) to be occurring in a thrust fault zone located at the base of the landward wall of a trench. Tectonic erosion and subduction assisted by pore-pressure phenomena, alluded to in the subject article, are used to explain the perceived absence of material in the forearc—for example, absence of byproducts of thrust faulting such as accreted oceanic rocks and accreted trench fill. The concept of tectonic erosion is based on and requires the major thrust fault of the plate tectonic model. The fault accommodates the assumed long-term (millions of years), continuous, rapid convergence of the plates. This model convergence balances reported seafloor spreading.