The dune and swale topography is easiest to see in the Miller Woods area of the lakeshore. Much of the dune and swales was eliminated by the construction of the industrial plants of Gary, East Chicago, Whiting and Hammond.
Miller Woods is an example of a rare land form known as “dune and swale”. Many thousands of years ago, Lake Michigan extended into this area, and as the lake receded, it built and left behind a series of dunes along its edge.
This globally rare natural community only occurs along the Great Lakes shoreline. Water levels of nearby Lake Michigan often affect the swale, depending on the height of the dune ridge in relation to the water below. While the swales closer to the shoreline become flooded as water rises of the top of the ridge, inland lakes flood more often because of groundwater rolling down the hills and other drainage. Wind and weather also play integral roles in the formation of the dunes and swales.
Though not very tall, these dunes once extended lengthwise for miles, roughly parallel to the present-day lake shore. Between each adjacent pair of dunes was a low area, or swale. The result somewhat resembled a giant washboard, with dunes and swales paralleling and alternating with each other.
Old aerial photographs of this area reveal a striking striated pattern wherever the dune and swale system survived. The swales often fill with water; at the least, they tend to be wetter than the adjacent dunes, and this variation in soil moisture leads to an unusually high species diversity. Alas, commercial and residential development has obliterated most of the dune and swale complex.
The opening of U.S. Steel started a period of industrialization and growth in Gary. Prior to this industrialization and resultant commercial and residential development, Gary and the northern part of the Morainal Natural Region were characterized by a dune and swale system that includes upland dunes interspersed with wetland swales.
Dune and Swale Complex
A dune and swale complex is a series of roughly parallel, sandy ridges and low, wet swales formed from irregular cycles of high and low water levels. Dune and swale complexes are also commonly known as linear dunes, beach ridge complexes or shore parallel dune ridges. These natural communities are significant for their concentration of biodiversity in a small area.
Linear dunes are the high points above the valleys of swales in the dune and swale complex systems. These dunes also consist of four zones: beach and foredune, open interdunal swales, forested dune and ridges, and forested swales.
Open marsh with grasses, sedges, and ferns dominate the lower part, or swale, of the system. Cattails typically associated with wetlands do not occur in swales since the water level is too low and intermittent to sustain the viability of the plant.
Wooded dune and swale complex is a large complex of parallel wetland swales and upland beach ridges (dunes) found in coastal embayments and on large sand spits along the shorelines of the Great in Minnesota, Wisconsin, Michigan, Illinois, Pennsylvania, Ohio, Indiana, and Ontario. They were formed in two stages by retreating water levels and post-glacial uplift beginning with glacial Lake Algonquin approximately 12,000 years ago. As lake levels progressively receded, they deposited a series of low, parallel, sandy beach ridges ranging in height from 2 ft to 12ft. The alternating sequence of arced sand ridges and associated swales often extends up to two miles inland. The upland dune ridges are typically forested, while the low swales support a variety of herbaceous or forested wetland types, with open wetlands more common near the shoreline and forested wetlands more prevalent further from the lake.
Given the complexity and variation of wooded dune and swale complexes, soils can range from calcareous sands in the foredunes to deep acidic peat or alkaline marl in well-established swales.
Wooded dune and swale complexes formed as a result of receding Great Lakes water levels and post-glacial uplift that created a series of parallel, arced, low sand ridges and swales. Vegetative succession has since created a distinct pattern of communities or zones across this landscape complex. The flow of surface streams and groundwater is critical for maintaining saturated to inundated conditions in swales. Because of the close proximity to the shoreline, windthrow is common, especially on the loose organic soils of swales where anaerobic conditions limit the rooting depth of trees. Along-shore currents, waves, and wind create and continuously re-work foredunes along the shoreline. Additional important components of the natural disturbance regime include fire, beaver flooding, and insect epidemics.
Swales are the troughs or low-lying land separating the dune ridges. Originally wet and marshy, the swales dry out over time. The progression from wet to dry swales can be seen as one moves further inland.
Dune and swale complexes are series of roughly parallel dunes that form as the water level of the lake gradually drops. These dunes may form in bays which are gradually being filled in by sand deposits.
The complex is produced by a series of foredunes forming as the beach "grows" out into the lake. Each new foredune eventually cuts off the sand supply to the inland dune. The result is a series of low dunes, generally less than 15 feet in height.
The landforms along the Lake Michigan coast today have ages ranging from just a couple of months to thousands of years. Dunes started forming when the ice sheet retreated because the glacier left sediments behind and there were strong winds to move them around. The landscape changed as the level of the lake rose and fell, climate and ecosystems varied, and human activities took place along the coast. Dunes grew, eroded, became stabilized, were reactivated and were overridden by other dunes.
Coastal dunes are dynamic landforms—they grow, erode, change shape, and move across the landscape as wind interacts with the dune environment.
Coastal dunes are landforms of sand, shaped by the wind in coastal areas. For a coastal dune to form, three things are needed: 1) available sand, 2) winds of sufficient strength to move the sand, and 3) vegetation (or another obstacle) that causes the sand to pile up.
The shore of Lake Michigan is a great location for dune formation because there are large amounts of sand available along the coast, there are strong westerly winds to move the sand inland from the beaches, and the moist climate supports the vegetation that starts dune growth.
Here's map of the trail system. You will begin at the parking area and walk from the swale area to the dunes and back. Be prepared for a long hike. To answer the questions, you'll have to complete the entire trail.
1. Describe the swale that you see at the posted coordinates.
2. Describe the difference that you see when you get to the dunes. How different is it from the swale at the beginning of the trail.
3. How tall are the dunes at the lakefront end of the trail.
4. Post a picture of yourself (face not required) or a personal item at the Lakefront.