(The following is taken from Centennial History of Polk County by T. M. McCall, McGarry Publishing Co., Crookston, MN. 1961.)
It may be difficult for people today to believe that great glaciers once moved down from the north and that these great sheets of ice moved across the length of Minnesota and extended down into Iowa~ that the great lobes of ice, as they planed off the surface of the land, left great deposits of soil and rocks which formed terminal moraines which held back the water as the ice melted. (Moraines are accumulations of debris along the edges of glaciers.) The enormity of the ice sheet and the volume of water challenges the imagination as geologists unfold the history to us.
Mute evidence that a great ice sheet did move over Minnesota can still be seen today in the planed-off outcroppings of the original granite near Clementson, and the bald granite ridges in southern Ontario, Canada. Other cumulative evidence of the action of the ice sheet lobe in this area can be seen in the terminal and lateral moraines of the southern counties of the Red River Valley and in the definite shore lines of the receding glacial lake which are apparent on both the Dakota and Minnesota sides of the Red River Valley.
A famed geologist, Warren Upham, did pioneer work in tracing shore lines of the great glacial lake for the Minnesota Geological Survey and the United States Geological Survey. The name Lake Agassiz was given this prehistoric glacial lake by Warren Upham in 1879 in the Eighth Annual Report of the Minnesota Geological Survey According to Upham, the first true explanation of the lake's existence was presented by a geologist professor of the university in 1872. Upham reports, "while the retreating ice sheet served as a dam to prevent water from the melting ice to flow northward, the overflow did go south through the Lake Traverse and Big Stone Lake area, through Brown's Valley to cut out the channel of what is now known as the Minnesota River Valley . This glacial river, which carved out the Minnesota River Valley , was named River Warren by Upham.
Another famed geologist, who collaborated with and followed up the work of Upham, was J. E. Todd. Todd, in Chapter V of the 1896-97 Report of the Minnesota Geological Survey, Volume 4, gives an excellent report on the geologic history of Norman and Polk (including Red Lake) counties.
In discussing the history of the glacial Lake Agassiz, Todd reports,. .."In its (the glacier's) recession, we suppose that it had periods of halting and possibly advancing for short distances, which has, as before explained, resulted in the accumulation of moraines. Between the Red River lobe, as we may call it, and the Lake Superior lobe, which occupied the upper Mississippi region, there was at one time no distinct separation upon the surface of the ice sheet, but as they melted away their margins would very naturally be more and more separated along the height of land or ridge forming the divide between the Mississippi basin and that of the Red River."
In tracing the shore lines of beaches of glacial Lake Agassiz, Upham found that their elevation of the highest crest of the Herman beach in Polk County was 1,173 feet above sea level, which would indicate that a water depth of 300 feet stood over what is now Crookston. Upham states: " Several successive levels of Lake Agassiz are recorded by distinct and approximately parallel beaches of sand and gravel due to the gradual lowering of the outlet by the erosion of the channel at Brown's Valley and these are named in their descending order, Herman, Norcross, Tintah, Campbell and McCauleyville beaches, because they pass through or near these towns. "
For more information see: