A Hope College professor is taking the long view of sand dune movement, tracking the way they've behaved for the past 5,000 years.
"The basic idea is to find out when the dunes began to form; find out when they were active -- in other words, when were they growing and moving; and find out when they were stable -- when they were sitting in one place," said Dr. Ed Hansen, professor of geology and environmental science and chairperson of the department. "And eventually to try to figure out why they're sometimes active and sometimes stable."
He is interested in the topic as a research question, but he also appreciates the practical benefits of better understanding the dunes' behavior. "If we've got an idea of what the natural history is, it would be easier to manage them," he said.
Hansen recently received support for his research through a $50,000 grant from the Petroleum Research Fund. The grant will provide stipends for Hope student researchers, laboratory testing and materials for the next three years.
Hansen has been studying the dunes in the Holland area since 1998.
"We now have worked out a really detailed history around Holland," he said. "We probably have one of the most detailed histories of a dune complex ever worked out."
Through the new grant, he will choose four or five other sites along the eastern coast of Lake Michigan to develop a more complete view. "When we're done we should be able to generalize--to have a general dune history--for the southern part of the lakeshore, for the area roughly from Muskegon south," he said.
According to Hansen, the dunes formed about 5,000 years ago. The lake prior to that time had been much lower than it is today. It subsequently rose to a height several feet higher than its present level and then fell quickly, which is when the dunes developed.
In the Holland area, he noted, the more inland dunes stabilized and became forested, as they still are, about 4,000 years ago. The dunes closer to shore were fairly fluid until about 2,000 years ago, at which time they became stable for some 1,500 years.
The dunes locally started shifting again about 500 years ago, behavior that continues. Hansen and his team have tracked one area shore dune moving inland at a rate of about 4.5 feet per year.
Hansen notes that researchers don't yet know what prompted the times of stability and movement. "We would love to know why," he said.
One implication, however, is clear: the phenomenon of dune movement isn't man-made. "Certainly some of the things we do may enhance it, but it started before any Europeans came and cut down the first tree or someone rode the first off-road vehicle," he said.
To map the history of the shoreward dunes, Hansen has charted tell-tale signs in the sand: visible lines of dark soil that run horizontally through today's dunes. "What they are is the top soil, essentially, of a former surface of the dune," he said. Radio carbon dating helps determine the age of the former surfaces.
For the wooded back dunes, where former surface soils are hidden, he and his team do some digging to collect soil samples, and have another form of testing done to determine how long the sand has been buried: optically stimulated luminescence, a new technique that essentially reveals how long the sand has been out of the sun.
Hansen is conducting his work on dune history in collaboration with Alan Arbogast of the Michigan State University faculty. He is also engaged in another project that looks at more recent dune behavior, work that he conducts with Deanne van Dijk of the Calvin College faculty.
He has made multiple presentations at professional conferences concerning his research. During the 2003 annual meetings of the Michigan Academy of Science, Arts and Letters, held at Hope in March, he led a special session on "The Geology and Geomorphology of the Lake Michigan Coast" that included a trip to the area dunes and presentations by specialists from Michigan, Indiana, Wisconsin and Canada.