



You are looking at old interglacial shorelines. During those brief (between Ice-Age) warm periods, sea level rose higher than today's level. About 110,000-years ago, the ocean rose perhaps three- or four-meters (10- to 13-feet) higher than present. Even without taking into account global warming's effects, we have not reached our "normal" interglacial high-stand.



All kidding aside, I understand that what you are building consumes many hours and involves many different steps to produce an interactive map. I am just very curious to what forgotton agriculture is still visible around Colliers Mills.
Unfortunately the USGS server maintenance schedule makes this impossible. In fact, I had planned to include those quads in last night's update but I couldn't download anything from USGS. So instead, I just built all the remaining quads that I could from data I already had.