Sponsored by the Geomorphology Specialty Group
Association of American Geographers 102nd Annual Meeting
Chicago, Illinois, March 7-11.
Aeolian Geomorphology IV
Paper Session 4417
Friday, 3/10/06, from 2:00 PM - 3:40 PM
Geomorphology Specialty Group
Coastal and Marine Specialty Group
Jean Taylor Ellis - Texas A&M University
Deanna Van Dijk - Calvin College
Deanna Van Dijk - Calvin College
2:00 PM Author(s):
*Deanna Van Dijk, Geology, Geography and Environmental Studies - Calvin College
Melinda C. Campbell, Geology, Geography and Environmental Studies - Calvin College
Anelia L. Tinklenberg, Water Resources Program - University of New Mexixo
Abstract Title: Foredune evolution on the east shore of Lake Michigan
Lake Michigan coastal dunes are dynamic landforms that respond to seasonal and year-to-year variations in wind, temperature, precipitation and lake levels. From 2000-2005, we studied the evolution of an active foredune in P.J. Hoffmaster State Park on the east coast of Lake Michigan. We used ground surveys, erosion pins and sand traps to measure erosion, deposition and sand transport. We installed instruments at the site to measure wind, temperature and humidity, and we recorded soil moisture, snow-cover, ice, ground-freezing and beach width during site visits. The foredune grew during the five years of study, with most of the growth occurring during the fall and winter when winds are seasonally strong. Dune growth varied considerably from year to year, with annual sediment inputs to the foredune ranging from 1.9 to 4.8 cubic meters per meter-width. Results also show significant variations in overall winter conditions and subaerial beach width. On the Lake Michigan coast, fall and winter sand transport by wind is not solely a function of wind speed. Wet, frozen or snowcovered surfaces reduce sand transport rates, and total amounts of transport depend on the size of the area which supplies sand to aeolian processes. At the time-scale of hours to days, surface conditions and weather dominate foredune changes, but lake-level changes determine the long-term evolution of the foredune.
Keywords: aeolian geomorphology, coastal dunes, Lake Michigan
- 2:20 PM Author(s):
*Edward Hansen, Dr. - Hope College
Abstract Title: Morphology of Massive Parabolic Dune Complexes, Southeastern Coast of Lake Michigan
Complexes containing massive (relief 25-50 meters) parabolic dunes along the southeastern shore of Lake Michigan fall between two extremes. Simple complexes contain a single set of massive parabolic dunes. Compound complexes consist of several generations of overlapping parabolic dunes behind a linear coastal dune ridge. Foredunes develop during low lake levels in both types, but are more extensive in the compound complexes. Relatively low, wooded beach dunes occur along the inland edges of both types of complexes. Radiocarbon ages from dune paleosols and OSL ages below dune surfaces suggest that the timings of episodes of dune growth, migration, and stabilization were the same for both kinds of complexes. Exposures of paleosols along the lakeshore indicate that simple complexes developed in areas with a net eastward (landward) migration of the shoreline. In these areas net erosion has been greater than sediment supply and the massive parabolic dunes migrated inland as their lakeward edges were destabilized by wave erosion. Fragments of older coastal dune ridges in the compound complexes suggest that they were formed in areas where net sediment supply was greater than erosion causing a net westward migration of the coast. Accretion of foredunes formed successive generations of coastal dune ridges. Blowouts in these ridges led to different generations of massive parabolic dunes. Thus, while climate or lake level may determine the timing of dune growth and migration, relative rates of sediment supply and erosion appear to determine the morphology of dune complexes.
Keywords: dunes, Lake Michigan, coasts
- 2:40 PM Author(s):
*Robert Vink, Geology, Geography and Environmental Studies - Calvin College
Deanna Van Dijk, Geology, Geography and Environmental Studies - Calvin College
Abstract Title: Wind or Human Activity? Changes to a Michigan Landmark Dune
Mt. Pisgah is a large parabolic dune in Holland, MI, on the east coast of Lake Michigan. The dune is a historic landform located near Holland State Park, the most-visited state park in Michigan with more than 1.5 million visitors per year. Prompted by local concern that Mt. Pisgah is shrinking, this study investigated the current activity of the dune, along with historic changes to the dune. We mapped dune topography and surface characteristics with an electronic total station. We used photographs, interviews, and questionnaires to collect information on the history of Mt. Pisgah and visitor activities. We also recorded numbers and activities of people on the dune. Results show that Mt. Pisgah is an active parabolic dune shaped by aeolian processes and human activities. The dune has no sediment inputs from the beach, but local reworking by the wind moves sand from the exposed upper backslope to the dune crest and upper slipface. Distinctive signs of human influence are the enlargement of the exposed area on the dune backslope, the development of a notch across the dune crest, and a protruding lobe of sand?not aligned with the main axis of the dune?where there is a pathway on the dune slipface. Observations suggest that more than 3200 people climb Mt. Pisgah each year. Dune managers could mitigate the impacts of the visitors by installing a stairway and boardwalk to the dune crest, closing many surplus dune trails, stabilizing the exposed upper backslope with sandfencing, and planting vegetation.
Keywords: aeolian geomorphology, dunes, Lake Michigan, human impacts
- 3:00 PM Author(s):
*Mary-Louise Byrne, Geography and Environmental Studies - Wilfrid Laurier University, Waterloo,Ontario,Canada
Abstract Title: Sand transport and coastal dune evolution at Pinery Provincial Park, Ontario, Canada
Sand transport through a tough blowout at Pinery Provincial Park varies seasonally with smaller amounts during summer and larger amounts during the winter months. Morphologic changes in the dune occur over longer time spans. Examination of the erosion pin data collected over 11 years reveals that the surface of the lake-side of the dune is generally accreting in the late summer and fall and then eroding during the winter months. Lee slope erosion pins revealed patterns of deposition with significant volumes of sand contributed to the lee face of the dune during the winter months as snow and sand are blown up the throat of the dune. Summer erosion results in the lakeward transport of sand up the lee slope as ripples migrate with the prevailing summer winds. The result is a change in the morphology of the lee face of the dune. The toe of the lee face is building slowly outward (landward) while the upper portions of the lee face increase in slope. The lee slope builds landward and upward, dominated by tractional movement of sand punctuated by brief periods of avalanching.
Keywords: geomorphology, sand transport, GIS, GPS
Session Description: This series of three special paper sessions are co-sponsored by the Coastal and Marine Geography (CoMa) and Geomorphology specialty groups. The research presented in the paper sessions cover a broad spectrum of spatial and temporal scales within aeolian geomorphology.