Thunder Bay Shoal, also known as Thunder Bay Reef, is a notable geological feature located in Lake Huron within Thunder Bay National Marine Sanctuary, near Alpena, Michigan. It is one of the largest and most significant underwater reefs in the Great Lakes region.
The Thunder Bay Shoal is an expansive limestone reef that stretches over 7 miles (11 kilometers) in length and rises to within 3 to 6 feet (1 to 2 meters) of the water’s surface. The reef is made up of ancient fossilized coral formations and is home to diverse marine life, including fish, invertebrates, and plant species.
Due to its shallow depths and proximity to major shipping channels, the Thunder Bay Shoal has been the site of numerous shipwrecks over the years. More than 100 shipwrecks have been discovered in the vicinity of Thunder Bay, making it a popular destination for divers and maritime archaeologists.
To protect and preserve the historical and ecological significance of the area, Thunder Bay National Marine Sanctuary was established in 2000. The sanctuary encompasses an area of approximately 4,300 square miles (11,100 square kilometers) and includes the Thunder Bay Shoal and surrounding waters. It serves as a sanctuary for shipwrecks and promotes research, education, and the conservation of Great Lakes maritime heritage.
