A professor and a postdoctoral fellow at Northwestern who are part of an international geological research team will present their findings on post-glacial land movement today in Montreal at the Spring Joint Assembly of several scholarly geological organizations, including the American Geophysical Union and the Canadian Geophysical Union.
The glaciers that covered the Central Midwest melted thousands of years ago, but the land still move as much as a half-inch per year in the area, their research shows.
Although much of geological research focuses on events that occurred thousands or millions of years ago, the team’s research involves current issues and future concerns.
The team — composed of geological sciences Prof. Seth Stein and Giovanni Sella, who is a postdoctoral fellow, and other specialists from the U.S. and Canada — positioned between 100 and 150 antennae throughout the Midwest. Using Global Positioning System satellites to track the changing antenna heights, the researchers can to “see” how the land moves.
“Eighteen thousand years ago the glaciers compressed the land in the Midwest,” Stein said. “Once the glaciers melted, the land started rebounding, and is continuing to do that today.”
Rebounding occurs when the viscous mantle of the Earth fills in underground spaces previously blocked by the glaciers, Stein said.
The team decided to use GPS satellites to track the continent’s motions because the system can detect changes in level as small as 1/25 of an inch per year, Stein said.
This movement in the land is affecting the levels of the Great Lakes. The harbors on the south side of the lakes are sinking, causing water levels to rise, while the north side harbors are rising, leading to decreasing water levels. Shipping industries are impacted greatly by this change in the Great Lakes, Stein said.
Stein said another aspect part of the research is whether earthquakes in the Central Midwest and Canada are caused by glacial rebounding. If researchers can understand what causes the earthquakes, such as slow movement of the land, scientists can predict more accurately where earthquakes will occur, and use the knowledge to choose where buildings should be erected.
Geologists are especially interested in using the team’s research to gain a better understanding of the ice age and its climate. Stein said he and his colleagues are trying to establish a glacier history, in particular to determine how the ice melted.
But it is the main focus of the research — on changing land levels — that is exciting, said Prof. Donna Jurdy, chairwoman of NU’s geological sciences department.
“(This research) has a lot of significance in peoples’ lives,” Jurdy said. “New Jersey is sinking because Canada is rising.”
