Figure 11: GPR profile (ESTR) from the southern end of the Clatsop subcell. The profile shows two slump scarps on the seaward side (figure left) of the Big Dune Ridge. The landward-most extents of the foredune ridge disturbance zones (FDDZ) occur at 280 m and 330 m distance along the profile. These two distances (280 and 330 m) are used to establish the maximum landward positions of the prehistoric shoreline for the last two prehistoric retreat events, A and B respectively, on the ESTR profile.