Acoustic data from Lake Johnson is generally poor due in part to a strong lake bottom multiple, signal attenuation and technical difficulties. Parallel, horizontal reflections are present above 12 ms (8.7 m below lake surface) that may represent in situ and transported Plio-Pleistocene sands (Type 6, A-A’). Below 12 ms, only “windows” of interpretable data are present. Sections of the data can be resolved to approximately 32 ms (10 m). High angle reflections suggest collapse of material into a large sink (Type 1, A-A’) and smaller, concave reflections that suggest subsidence into smaller sinks or dissolution pipes (Type 4, A-A’).

Lake Johnson appears to have formed by the coalescing of many collapse sinkholes. After the initial collapse of an individual sinkhole, the sides have eroded into the central portion of the sink, flattening the banks and filling the center. A very steep-sided, deep sink is located near the entrance of the adjacent Gold Head Branch State Park and may represent the younger stages of this process. The area where the seismic profiles were run is relatively flat bottomed and shallow, indicating a more mature feature. Flow into Lake Johnson with no outflow indicates direct recharge to the aquifer.