Lake Whittlesey was a proglacial lake that was an ancestor of present-day Lake Erie. It formed about 14,000 years ago. As the Erie Lobe of the Wisconsin Glacier retreated at the end of the last ice age, it left meltwater in a previously-existing depressional area that was the valley of an eastward-flowing river known as the Erigan River that probably emptied into the Atlantic Ocean following the route of today's Saint Lawrence River. The lake stood at to above sea level. The renament beach is not horizontal as there is a ‘hinge line’ southwest of a line from Ashtabula, Ohio, through the middle part of Lake St. Clair. The hinge line is where the horizontal beaches of the lake have been warped upwards towards the north by the isostatic rebound as the weight of the ice sheet was removed from the land. The rise is north into Michigan and the Ubly outlet. The current altitude of the outlet is above sea level. Where the outlet entered the Second Lake Saginaw at Cass City the elevation is above sea level. The Lake Whittlesey beach called the Belmore Beach and is a gravel ridge to high and one-eighth mile (18 meters) wide. Lake Whittlesey was maintained at the level of the Ubly outlet only until the ice melted back on the "Thumb" far enough to open a lower outlet. This ice recession went far enough to allow the lake to drop about below the lowest of the Arkona beaches to Lake Warren levels.