Lakes are a disruption of surficial runoff processes and are typically formed after disturbances, such as glacial deposits, landslides, eruptions which disturb river flow. They may last many lifetimes of people, but they don’t last long in a geological sense. The old shorelines of Lake Superior record old lake levels that have changed since the glacial retreat. In the future we should expect Lake Superior to drain away as a new outlet for its water naturally develops. The same applies to the inland lakes of Minnesota, Wisconsin and Michigan: they are all relicts of those glacial times. Some of the inland lakes will develop into bogs and others will drain away into extending river systems.
Lake Superior is considered a “young” lake (Oligotrophic), and is likely to last millenia unless man’s activity impacts.
Satellite View of effects of the floods of May 2012 which produced dramatic sediment increases in Western Lake Superior (NOAA and Minn Sea Grant).
