Large planation surfaces have been documented around the world. Secular geologists are hard pressed to explain them, while diluvial explanations appear reasonable. Such a large-scale planation surface is documented on the Canadian seaboard. It appears to be a dissected planation surface covering over 800 km in Nova Scotia, Newfoundland, and Labrador. Of the possible explanations for its origin, only one appears to fit the facts of the field: A large, fast-flowing sheet of water eroding the rocks of the area. It has yet to be determined if erosion happened at today’s elevations or whether there has been subsequent uplift. It is possible that many identified unconformities are simply planation surfaces distorted during uplift.