Drive in from Esch Road
Traversing
up the East Side of the Empire Escarpment of the dunes N44° 53' 29.26" W86° 02' 39.03"
Sleeping Bear Dunes
I recently spent some time at Sleeping Bear Dunes -located near Empire, Michigan (zoom out on the map a bit, it's ridiculously close). The Dunes are interesting in a unique way because of the height from the Lake Shore and the nearness to the shoreline. However, the visitors center display tells us these formations are not really dunes, they are stratified glacial deposits. And in truth, as I tried to point out with some of my photographic efforts, there is a goodly mixture of pebbles, rocks and sand all through out the region. True dunes are pictured on the right column and are purely the resulting deposit of wind forces-From Wikipedia
In physical geography, a dune is a hill of sand built by aeolian processes. Dunes occur in different forms and sizes, formed by interaction with the wind. Most kinds of dunes are longer on the windward side where the sand is pushed up the dune and have a shorter "slip face" in the lee of the wind. The valley or trough between dunes is called a slack. A "dune field" is an area covered by extensive sand dunes. Large dune fields are known as ergs.
Some coastal areas have one or more sets of dunes running parallel to the shoreline directly inland from the beach. In most cases the dunes are important in protecting the land against potential ravages by storm waves from the sea. Although the most widely distributed dunes are those associated with coastal regions, the largest complexes of dunes are found inland in dry regions and associated with ancient lake or sea beds.
The shoreline along Lake Michigan has become a new fascination for me. I plan to go back and would like to eventually live much closer to that area. I wanted to present a smidgen of the literature that I have been perusing by gathering it all on one or two pages rather than have the reader chase around the web with a plethora of web links.
The U. S. Geological Survey website has an interesting bit about Sleeping Bear and this will be my starting point for this discussion The writer discusses the formation of beach ridges-some of those are visible in the pictures on the right-these indicate former positions of the shoreline and are a clear indication that the lake levels are continuously dropping. Indiana Dunes is along the Southern shore of Lake Michigan that stretches between Michigan City and Gary, IN. It is in many ways, a sister site to Sleeping Bear and is equally popular for visitors to hike, swim and camp. From the U. S. Geological website:
Bedrock lies far beneath the surface and large moraines, beach ridges, and sand dunes preserve a record of the glacial history and subsequent lake-level changes of this area. Indiana Dunes NL at the southern end of Lake Michigan represents the largest strandplain of beach ridges in the Great Lakes with about 150 distinct ridges that have evolved over the past 6000 years (Thompson, 1992). In the past 2600 calendar years beach ridges have formed about every 30 years due to lake level changes and the rate of sediment supply to the area (Thompson and Baedke, 1995). Colman and others (2000) estimated that sediments are being deposited in the basin of southern Lake Michigan between 4 and 11 times faster than in the 5,000 years before human settlement, which would suggest a higher rate of erosion of the lakeshore due to lake-level change or changes in land use. Indiana Dunes National Lakeshore is home to one of the most diverse biological communities per unit area of any of the national parks. For more information on Indiana Dunes National Lakeshore see: http://www2.nature.nps.gov/geology/parks/indu/index.cfm
I have some pics of the Platte River mentioned above-in the first one on the right the river shoreline is barely a thin trace as it merges into the lake. -Copy and paste the coordinates into Google Maps -satellite version-to find the exact location of each photo. From Wikipedia
The Platte River is about 28 miles (45 km) in length from its origin in Lake Dubonett. The watershed area is about 193 square miles (500 km2). The land coverage is 82% forested, open lands or wetlands; 12% agriculture, and 7% urban. Approximately three quarters of the watershed is publicly owned lands. Water in the river is clear due to extensive wetlands. Mixed conifer and hardwood wetlands give way to tamarack and arborvitae swamp near Platte Lake.
From the scientific literature and I will subsequently post some pictures of the phenomena listed here; popularity of the Lake Michigan dunes, the human impacts of building and developing (even a National Park-when it is heavily utilized-counts as a development) and the formation of the earliest ridge and trough just before the current tree line. The Sleeping Bear dunes are termed perched Dunes because they were moved on top of glacially deposited till that in itself is quite high off the water line. Traversing the dunes on foot, a person can actually see the sand formations changing in some places (especially on top of the escarpments) as the sand blows across the landscape.
Scientific observations of the dunes start with the fact that they are unique to the area-the Michigan coast of Lake Michigan-and have a large number of potential users-35 million people live in the Great Lakes basin.
As human impacts on these sensitive landscapes increase, however, they may be destabilized and extensively mobilized (Santer 1993, Harding 1994). Thus, critical habitats may be lost and significant dollars spent by various agencies and landowners to control dune erosion (Harding 1994) To plan for protection and use of coastal dunes in Michigan their natural evolution must be fully understood. In terms of genesis, Great Lakes coastal dunes have been broadly classified in two ways: 1) as foredunes or beach-margin dunes (Olson 1958a); and 2) as “perched” dunes (Olson 1958, Marsh and Marsh 1987).
Of the two categories, beach-margin dunes have been studied the most, particularly in association with beach ridges and late Holocene lake-level change. Beach ridges form when lake level falls and sand from the new (lakeward) beach is deflated and deposited on the wider back beach such that a sublinear dune a few meters high is constructed. Further fall in lake level builds a similar ridge lake- and parallel to the first and, eventually, in a series of ridges roughly paralleling the shore. Whenever a new ridge begins to build the older ridge stabilizes and peat begins to develop in the poorly drained, intervening swale. The base of these peats can then be radiocarbon dated, which provides an estimate of when building of the more lakeward ridge in a ridge couplet began. This age, in conjunction with the elevation of foreshore deposits buried by the more lakeward ridge, can thus be used to reconstruct lake elevation at the time of ridge formation. Using this approach, extensive beach ridge sequences (100 + ridges) have been used to develop late Holocene hydrographs of Lake Michigan (Larsen 1994, Thompson 1992, Johnson et al. 1990, Dott and Mickelson 1995, Lichter 1995, Thompson and Baedke 1997).
Some details regarding the geomorphic evolution
of perched dunes have recently emerged. Two
prominent perched dune systems in Michigan,
Sleeping Bear Dunes and Grand Sable Dunes, are
located leeward of lake-facing bluffs that are approximately
90-m high (Santer 1993). In contrast to
the low-lying beach ridges, the sediment source for
perched dunes is the upper part of the adjacent
bluffs, which destabilize when the lower bluff is
undercut during high water. This disruption subsequently makes eolian transport of sediment
(from
the upper bluff face) more likely (Olson 1958, Snyder
1985, Marsh and Marsh 1987). At the Grand
Sable dune field, Anderton and Loope (1995) correlated
episodes of dune building and stability with
the late-Holocene lake hydrographs reconstructed
from beach ridge studies (Thompson and Baedke
1997). They argued that dunes began to develop as
the rising waters of ancestral Lake Nipissing cut a
bluff into a high forested plateau of unconsolidated
sand about 6,000 radiocarbon years before present
(yr B.P.) Subsequently, between four and eleven
major periods of dune building buried former stable
surfaces (represented by soils). This model supports
previous research (Olson 1958, Marsh and Marsh
1987) linking building and immobilization of
perched dunes to high and low water, respectively.
According to unpublished reports by Snyder (1985)
and Loope et al. (1995), the Sleeping Bear Dunes
on Lake Michigan probably evolved in a similar
manner.
In addition to the well-defined beach-margin and
perched dunes, another type of dune system exists
along the eastern shore of Lake Michigan that is
unique but poorly understood. These dunes are
similar to beach-margin dunes because their base is
relatively close to the shore when compared to
dunes perched on high bluffs. The dunes are much
larger (> 30 m) than beach ridges, however, and are
parabolic rather than sublinear in plan view. These
dunes are also comparable to classic perched dunes
because they mantle elevated surfaces. In contrast
to high plateaus (Sleeping Bear, Grand Sable), however,
these surfaces are much lower pro-glacial lake
terraces (Taylor 1990). Overall, these lake-terrace
dunes are easily the most common dune type along
the eastern shore of Lake Michigan, extending from
Manistee, Michigan to Indiana (Fig. 1). Contained
within this belt of dunes are some of the most spectacular
parks in the region, including Indiana
Dunes, Warren Dunes and Saugatuck.
Ecology, Evolution and the physical environment of our world
Ecology is the science devoted to finding order in the natural world; this is done by determining a frequency distribution pattern for all living things. In other words ecologists pose and answer question such as: why are there a certain number of maple trees in the Northeastern forests, or why are that many penguins standing on the coast line of Antarctica?
The Natural world is held in dynamic equilibrium as life replenishes it. The natural world is shaped by physical and bilogical forces that process the influx of light and heat the flows ultimately from the sun. Patterns in nature are understood by a study of evolution. Ecology involves the study of how organisms spend much of their effort in living out of equilibrium-heat, water and nutrients are not always available in exactly the optimal quanities-an organsim will have to rely on built in mechanisms to pull the internal temperature, water or nutrient balance in line with the external availability. If this is not possible, the organism may move or perish. The life on the Dunes gives one a chance to see how this is done as the environment for say Dune grasses moves from a population of zero to a maximum sustainable number. This is the theoretical limit or carrying capacity that a particular spot, region, ecosystem has.
