DUNE FORMATION This beautiful wildlife poster is brought Winds, blowing shoreward at speeds of 8 to 25 to you by the thousands of citizens who miles per hour, begin to move the sand grains. The have contributed to the Nongame Wildlife size of the grains which are moving is directly re- Fund on their state tax form or by a direct lated to wind velocity – lager grains require higher donation to the fund. It portrays the unique, wind speeds. These bouncing sand grains resemble tiny, skipping ping pong balls as they are moved by fragile, beauty and ecological value of sand the wind through a process called saltation (see fig- dune habitats, one of the most important el- ure 1). Colliding with each other, barely a foot or two ements of Michigan’s rich natural heritage. off the ground, they may meet a slight obstruction, such as a clump of grass, which deflects the wind and allows sand grains to drop. Thus a slight mound MICHIGAN COASTAL DUNES or hummock is created. INTRODUCTION Michigan’s shoreline is a showcase for 275,000 acres of sand dune formations. An interaction be- tween blustery winds and waves has moved and Suspension carved fine sands into the largest display of fresh- water dunes in the world. These beautiful sand Wind Saltation formations contain a diversity of life, climatic con- ditions, and geological relief unique to Michigan. Saltation Creep A visit to a sand dune provides an opportunity to experience a landscape of natural sounds, smells, and sights. Feeling the clean sand beneath your feet as the fresh lake breezes bathe your face is one of the values of Michigan’s magnificent sand dunes. We have a responsibility to protect and preserve this natural legacy for the enjoyment and Figure 1. Sand movement by wind: saltation and wise use by our present and future generations. surface creep. We hope this poster will enhance your enjoy- The wind continues to push sand grains up the wind- ment and appreciation of the sand dune ecosys- ward side of the dune crest, causing the dune to grow tem by introducing you to its geology and ecology, in the downward direction. Many sand grains continue as well as to the human impact of this unique, moving and eventually roll down the steep backslope. A fragile environment. dune is slowly being formed, and its continued growth depends upon perennial vegetation, wind, and sand. GEOLOGY Because dune plants act as barriers to sand move- Michigan’s glacial history provides an explana- ment and hold migrating sand, they play a critical role tion for the formation of dunes. The Great Lakes in the formation and stabilization of dunes. dune complex is relatively young, in terms of geological time. As recently as 16,000 years ago, MAJOR DUNE TYPES Michigan was covered with glacial ice thousands Parallel dunes are a series of low, linear dunes of feet thick. The glacial ice contained a mix of formed parallel to the shores of large shallow bays. boulders, cobbles, sand, and clay. During glacial The parallel dunes along the eastern shore of Lake melting, this deposit was left and is known as gla- Michigan were formed about 4,000 years ago during cial drift. the Lake Nipissing stage of Lake Michigan, when wa- ter levels were 25 to 30 feet higher than present day This glacial drift is the source of sand in most Lake Michigan water levels. Rivers entering the bays of Michigan’s dunes. The sands were either erod- carried abundant sand, which was then moved along ed from glacial drift along the coast by wave ac- the shore by lake currents. tivity or eroded from inland deposits and carried by rivers and streams. Only the hardest, smallest, On-shore winds formed these sands into low-laying and least soluble sand grains were moved. Waves dunes. As the water level of ancient Lake Nipissing and currents eventually moved these tiny rocks dropped, a series of parallel dunes were created. They inland, creating beaches along the Great Lakes occurred in areas that were formally wide bays in Lake shoreline. Nipissing. Parabolic Today, some examples of parallel dune complex- Dunes es can be seen at the mouth of rivers, including the Muskegon, Kalamazoo, and Grand. Remnants of several ancient bays now are coastal lakes, such as dunes Axis of dune Hamlin Lake in Mason County, Silver Lake in Oceana County, and White Lake in Muskegon County. Parallel Onshore Wind Blowout Blowouts are saddle-shaped or U-shaped (para- bolic) depressions in a stabilized sand dune, caused Beach by the local destabilization of the dune sands. Blow- outs, which originate on the summit or windward face of a dune, are often rapidly formed by the wind, Figure 2. A blowout and parabolic dune inter- creating narrow channels and exposing plant roots. ruption of a Michigan shoreline. From: Bird, 1969, Blowouts can create interruptions in the shape of page 139 parallel dunes that may result in deeply carved in- dentions called parabolic dunes (see figure 2). It is Parabolic Dune the combination of interwoven parallel dune ridges that characterizes the classic dunes from Indiana, northward to Ludington, in Michigan. The moving sand from the blowouts often buries forest on the steep lee slopes. Blowouts may also AXIS uncover the bleached trunks of trees still standing after being buried in the dry sand for hundreds of years. These “ghost forest” are silent testimonials to ancient forests buried by blowouts in the past. DUNE LIFE ZONES Blowouts have historically been caused by natural The dune ecosystem is made of several zones disturbances, such as fires, wind storms, or plant with very different physical characteristics. They diseases. However, in recent decades, human activi- are as follows: ties and disturbances or destruction of sand-hold- ing vegetation has initiated blowouts. Off-road vehi- Beaches are zones where water meets land. The cle traffic and human foot traffic are major causes, constant movement of sand by the wind, pounding but clearing of protective dune vegetation to build storm waves, and winter ice and snow make this a homes, cottages, and commercial buildings has formidable habitat for any living thing. For this rea- also resulted in large-scale wind erosion-man –made son, few plants or animals live on the beach. Most blowouts. Continuous human disturbance has the wildlife seen there are just visitors. Among these potential for much more widespread destabilization visitors are scavengers ranging in size from small because it does not allow blowouts to stabilize. flies and beetles to shore birds, herring gulls, and even bald eagles. The remains of fish, birds, and Perched Dunes are some of the more famous and insects washed ashore provide food. most spectacular land features in Michigan. They are actually wind-blowing sand dunes perched atop glacial Mammals that venture down the beach include moraines. Glacial moraines, common landforms in the raccoon, skunk and fox, which wait until dark Michigan, are ridges of sand, gravel, stone or clay left to search the shoreline for food. A recent study by retreating glacial ice. The moraines lying along the conducted on North Manitou Island revealed an present shoreline of the Great Lakes were subjected unexpected scavenger: white-tailed deer that feed to wind and wave erosion. Sand, moved by waves and on dead alewives. long-shore currents, was blown up the steep faces of the moraines by on- shore winds, accumulating along The sea rocket is one of the few plants special- the summits and leeward sides, forming perched ly adapted to withstand the pounding of waves dunes. The famous dunes at Sleeping Bear Dunes and other adverse conditions. It sinks its roots to National Lakeshore are a well-known example. Others the water table and stores water in its succulent include those on the Manitou and Fox Islands in north- leaves. ern Lake Michigan and Grand Sable Banks near Grand The foredune is the first ridge behind the beach. Marais in Lake Superior. Although foredune are above wave action most of the time, they are regularly subject to storm es and sedges grow in the shallows. waves. Dune forests can be found on stabilized dunes protected from intense wind erosion. The domi- Like the beach, life in the foredune is a daily nant forest type varies as one travels north along struggle against shifting sand, scarcity of nu- the coastline. In southern Michigan dunes, oak- trients, rapid water drainage, high evaporation hickory forests are common. Northern dune for- rates, and storms. Out of the reach of waves, a ests are dominated by beech, maple and hem- few hardy plants, such as marram grass and sand lock. reed grass, are able to survive. These grasses are The uniqueness of dune forests stems from known as pioneer species, because they are one the fact that they develop on steep, barren sand of the first plants to become established, and slopes that are a short distance from open dunes. they create habitat for other plants by stabilizing The contrast between cool, shaded dune forest the soil with their extensive root systems, thus and the extreme temperatures and intense sun- increasing the soil’s capacity to retain water and light of the open dune can be striking. Through nutrients. Marram grass spreads quickly by send- thin and slow to accumulate, the topsoil of dune ing stems to the surface to form new plants. As forests supports a variety of spring wildflowers drifting sand accumulates in the marram grass, and woodland plants. the central stem continues to grow, keeping the plant’s leaves exposed to the sun and air. This Studies of dune slopes reveal varying patterns keeps the grass from being buried and increases of vegetation, depending on the direction of sun- the height of the foredune.