Active and passive continental margins. These cross sections (or vertical slices) through the Earth illustrate the differences between active (top) and passive (bottom) continental margins. A continental margin is the boundary between continental and oceanic crust. In the top diagram, it occurs at the trench, the topographic feature marking a convergent plate boundary. In the bottom diagram, the continental margin occurs below the continental slope. NJ is situated on a passive margin. The part of the cross section below from "rift basin" and to the right is very similar to the actual geology of the NJ continental margin.