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“Bite-Size Bits of Local, National, and Global History”
Idington in St. Louis County, Minnesota — The American Midwest (Upper Plains)
 

The Laurentian Divide

 
 
The Laurentian Divide Marker image. Click for full size.
By Christopher Light, July 12, 2009
1. The Laurentian Divide Marker
Inscription. The Laurentian Divide separates the watershed of streams that flow north to the Arctic Ocean from the watershed of streams that flow south through the Great lakes to the Atlantic Ocean. Where you are standing the divide is formed by a prominent array of hills known as the Giants Range. This ridge has been a highland for over two billion years.

The name "Laurentian" is used because the granites forming the ridge are similar to and were once thought to be related to, granites of the Laurentian Mountains in Quebec. Although this connection is no longer true, the name has remained.

The Giants Range is made up mostly of several types of granite formed several kilometers deep in the Earth's Crust about 2.7 billon years ago. Uplift and erosion slowly brought the granites to the surface: they have formed a highland throughout time because they are resistant to erosion. In the road cuts near the parking lot, crisscrossing bodies of darker and lighter granite record several successive intrusions of molten rock. Because of the complexity of the rocks, this site is known as "Confusion Hill" to local geologists.

About two billion years ago, the lower ground south of the highlands was covered by an ocean in which sediments were deposited. These sediments formed the rocks that include the world-famous Biwabik Iron Formation
The Laurentian Divide image. Click for full size.
By Christopher Light, July 12, 2009
2. The Laurentian Divide
of the Mesabi Range. About 80 million years ago during the Cretaceous period, sediments were again deposited in an ocean that lay south of the Giants Range.

Between two million and 10,000 years ago, glaciers that advanced and receded across this terrain removed most of the Cretaceous sedimentary rocks and scoured the older, underlying bedrock surface. Deposits of silt and gravel, and boulders left behind by these glaciers now cover most of the bedrock.
 
Erected 1998 by Geological Society of Minnesota, Minnesota Department of Transportation, and the Minnesota Geological Survey.
 
Location. 47° 45.099′ N, 92° 39.097′ W. Marker is in Idington, Minnesota, in St. Louis County. Marker is on U.S. 53 near Anchor Lake Road, on the right when traveling north. Touch for map. At the rest area on Anchor Lake Road. Marker is at or near this postal address: Forest Service Trailhead, Cotton MN 55724, United States of America.
 
Categories. Natural ResourcesScience & Medicine
 
The Laurentian Divide (Superior National Forest) image. Click for full size.
By Christopher Light, July 12, 2009
3. The Laurentian Divide (Superior National Forest)
The Laurentian Divide (Superior National Forest) image. Click for full size.
By Christopher Light, July 12, 2009
4. The Laurentian Divide (Superior National Forest)
Trailhead parking a Laurentian Divide
 
 
Credits. This page was last revised on June 16, 2016. This page originally submitted on July 23, 2009, by Christopher Light of Valparaiso, Indiana. This page has been viewed 3,600 times since then and 75 times this year. Photos:   1, 2, 3, 4. submitted on July 23, 2009, by Christopher Light of Valparaiso, Indiana. • Kevin W. was the editor who published this page.
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