Mean transverse H₂ column density profiles averaged in the longitudinal direction from 0 to 6 pc for the active region, and from 6 to 13.6 pc for the quiescent region. The left-hand-side (lhs) and right-hand-side (rhs) profiles denotes the eastern (i.e. from 0 to −0.63 pc) and western (from 0 to +0.63 pc) offsets from the spine centre. The red dashed line marks the position of a power-break that fits best the four profiles. We interpret this as the transition between the compact ridge and the more diffuse material surrounding the ridge.