The sediment swirls in this image extend out to the Duluth City limits near the intersection of Mc Quade Road and North Shore Drive, and just south of the Talmadge River. The water depth halfway across to Wisconsin's south shore is about 55 meters (180 feet).

Dynamic Lake Superior

You can also see that wave action along the south shore in Wisconsin is eroding the clay shoreline (the light tan area). It also appears that there is a a darker brown mass of material near the Duluth Inlet at the Aerial Lift Bridge which is an area where Harbor sediment is deposited, primarily from the discharge of the St. Louis River into the main lake. The striking swirls of turbid water illustrate how dynamic the lake is and how materials can be transported quickly from one area to another. Currents don't always follow the wind and water masses from coastal areas don't necessarily get diluted out with "cleaner" lakewater very fast. That is why it's so important to reduce Duluth's stormwater discharges and its connections to our sanitary sewers (WLSSD). Sewage spills during storms and spring runoff don't necessarily get instantly diluted out into the huge volume of Lake superior.

You can tell that it hasn't been raining because the St. Louis River and most of the Harbor are very blackish indicating that the river is not running very turbid as it would be after a big rainstorm or during high snowmelt runoff. But notice how reddish brown the southern part of the Harbor is where the red-clay laden Nemadji River enters the harbor.