My favorite cruise follows the St. Clair River northward from Detroit to Lake Huron and continues along the Canadian shore some 250 nautical miles to Georgian Bay and the North Channel. For generations this area has been widely regarded by cruising sailors as America’s premiere cruising area. Rugged and isolated, it is characterized by rocky shores and islands, deep crystal-clear water and excellent anchorages. En route, a series of day-long sails link small Canadian port towns which welcome sailors with safe harbors and modern, well- equipped marinas. Local grocery stores provide reprovisioning opportunities and restaurants offer a break from our galley fare. Typically, it takes 40 to 50 hours to sail to or from Detroit and the Georgian Bay, but progress is highly dependent on weather and winds. The Great Lakes form a chain. Lakes Michigan and Superior flow into Lake Huron, which empties into the St. Clair River to Lake St. Clair, a small (20x20 mile) and relatively shallow lake alongside Detroit. Lake St. Clair, in turn, empties into the Detroit River which flows into Lake Erie. Lakes Michigan, Huron, St. Clair and Erie can all be reached without canals or locks. The Georgian Bay amd North Channel are part of a geological feature called the Niagara Escarpment, a ridge of rock several hundred meters high in some places that stretches from Ontario to Wisconsin. The Niagara Escarpment dates back some 430 to 450 million years when the area lay under a shallow warm sea. It was located in a depression in the Earth's crust, the center of which is now the State of Michigan. Now geologically known as the Michigan Basin, the outer rim of the gigantic saucer-shaped depression forms the Escarpment, a horseshoe- shaped ridge that stretches from Tobermory, Ontario to Door County, Wisconsin. Rivers flowing into this ancient sea carried sand, silt and clay to be deposited as thick layers of sediment. At the same time lime-rich organic materials from the abundant sea life were also accumulating. Over millions of years these materials became compressed into massive layers of sedimentary rock and ancient reef structures now visible along the Escarpment. Sedimentary rock is clearly visible throughout the Georgian Bay and North Channel, such as at Flowerpot Island (photo) and George Island adjacent to Killarney. In addition, massive salt deposits lay under the area. These are still mined