While Great Lakes barrier systems look very much like oceanic barrier systems, in some cases their origins and the controls on their barrier systems are not as similar as their landforms make them appear. Here are some of the main comparisons this site has covered:
- Longshore drift. Regardless of location this is the dominant process that forms and nourishes both oceanic and lacustrine barrier landforms.
- Sediment supply. Both systems have a wide range of possible inputs, including input from rivers, reworking of the coastal platform, erosion of bluffs and headlands, nourishment from backshore dunes, deltaic deposits, glacial deposits, artificial nourishment, runoff from human-developed land, and biogenic material. In oceanic systems, river input and the reworking of the coastal platform create the largest barrier systems, while in the Great Lakes, bluff erosion of glacial sediments feeds the largest lacustrine systems.
- Coastal Platform. Both oceanic and lacustrine barrier systems require a shallow and flat shelf on which to build. In oceanic systems, the continental shelf most commonly provides the foundation, while in the Great Lakes, the platform can be provided by wave-cut glacial sediment or the deposition of river sediment.
- Influence of Glaciers. While glacial activity can provide sediment to and affect the formation of barrier systems, its role in oceanic environments is minor compared to that of Great Lakes systems. In the Great Lakes, they are responsible for most of the sediment (whether through coastal bluff erosion or eroded from the surrounding land and delivered through streams and rivers), for raising lake-levels due to glacial meltwater which cut platforms that serve as foundations, the deposition of debris and glaciolacustrine sediment that creates the substrate of the wave-cut platforms, and for the continued fluctuation of lake levels from isostatic rebound.
- Wind and Waves. In both systems, winds create waves which cause longshore drift, and erode, rework and transport sediment. In oceanic systems, wind a nd waves are extremely important as they shape the available sediment into the familiar barrier landforms.. Lakes, however, are more likely to be fetch-limited, which will also limit wave heights.
- Aeolian processes. Winds can also transport sand from the beach back into the dunes, removing it from the beach system. Additionally, Crowe, Coakley and Ptacek (1998) make mention of the fact that in the Great Lakes, the predominant winds blow directly onshore in many locations, increasing wind erosion, compared to the Atlantic coastline, whose predominant winds are not blowing east into coast.
- Landform Frequency and Size. In the Great Lakes, barrier systems tend to be smaller than oceanic systems, both in the size of the landforms and the overall extent and complexity. There are also no large barrier island complexes. There could be many explanations for this, including (1) like the Pacific coast, the coastal platforms are small compared to continental shelves, especially those of the Atlantic coast and its large systems of barrier islands; (2) there are no large rivers with extensive drainage basins, like the Mississippi River, that provide enormous amounts of sediment; and (3) the colder climate of the Great Lakes prevents high erosion rates year-round.