GLACIAL ROCKS

A million years ago glaciers moved into what became Iowa. Most of the northern hemisphere was covered by great ice sheets during the Pleistocene epoch. Mile-thick rivers of ice flowed down from the north to grind, tear, and pile the earth, creeping across parts of Iowa at least four different times between one million years ago and 11,000 years ago. The last two glaciers didn’t extend as far south as Jones County, so it has been 500,000 years since ice covered our local countryside. Still, our undulating hills that Grant Wood loved to paint were sculpted during the periods of glaciation in which the action of ice shaped the land.

Grant Woods Young Corn

Grant Wood’s Young Corn

When the glaciers receded about 11,000 years ago, they left behind rich soil. The extreme fertility of our soil is due to the climate and the prairie grasses, the earlier earthquakes, volcanoes, floods, and those four glaciers that ground rock into “glacial till”, mixing it with crushed and dieing vegetation. It is estimated that 70% of original American grasslands were formed on deposits created by glacial ice, lakes, stream, and winds.

Iowa is covered with glacial drift — rich soils evolved from rock, minerals, plants, animals, bacteria, temperature extremes, moisture, fire, insects, decay, time, and sun. The prairie soil that blankets Jones County developed in a temperate, relatively humid climate under tall grass. It is alluvial soil, made from sand, mud, etc. formed by flowing water. And it is loam — consisting of a friable (easily crumbled) mixture of varying proportions of clay, silt, and sand. The Iowa board of Immigration’s 1870 publication describes the soil: “It is supposed that there is no where else on the globe an equal area of surface with so small a proportion of untillable land as we find in Iowa. The soil is generally a drift deposit, with a deep covering of vegetable mold, and on the highest prairies is almost equal in fertility to the alluvial valleys of the rivers in other States. The soil in the valleys of our streams is largely alluvial, producing a rapid and luxuriant growth of all kinds of vegetation….”. In 1881 the state geologist pronounced 95% of the surface of Iowa to be tillable. Our land is among the richest in the world.

Besides the shape of our hills and the soil under our plow, the glaciers left us some mementos — rocks! Technically called glacial erratics, boulders that were drug from other places can be seen in our area. Some are so large that they are in the same exact spot where a glacier left them.


John Lacock’s farm, 11806 Hwy 64, Wyoming, In Madison Twp., just n.e. of Olin corners.

The sea covered the central part of North America, resulting in the development of thick marine limestone. Varieties of fossilized marine animals were once commonly found in rocks along the Wapsipinicon River. Our county lies in the Southern Iowa Drift Plain and the Mississipian system of rocks. The vast majority of erratics are igneous or metamorphic rocks, rather than the usual sedimentary rocks of sandstone, limestone, dolomite, and shale that constitute the bedrock under most of Iowa. A granite erratic would be rare but the glaciers did bring some. There are more erratics in northwest Iowa which had all four glaciations. Most erratics appear worn and rounded from their journey under and in the ice:

North side of road E63, about 3 miles west of Welton in Clinton County


Allen Cook’s farm, 66 Rd. Y24, approx. 2 miles n.e. of Massillon in Cedar Co.

Pioneer farmers were the first generation of several to deal with the immovable objects. The flat prairie land was often full of large rocks. After the stumps were pulled, it was time to remove the rocks. The smaller rocks were hauled over to the fence rows. The larger ones were left in the fields for the 20th century’s bulldozers and end loaders, but the largest of all still lay where mother nature placed them. Allen Cook claims to have a 14 foot glacial rock buried on his farm north of Massillon. The largest rock that I located in Jones County happened to be on the farm where I grew up, now owned by Dennis and Diane VonSprecken, 3272 Massillon Rd., Oxford Jct. in Oxford Township. In the 1980s, after having damaged farm equipment when they hit it, VonSpreckens tried to excavate it with a bulldozer and discovered it to be approximately 20 feet by 20 feet, too big to budge. It was covered with a layer of soil, promised it would be avoided with equipment, and left in its final resting place. From the road one can only see the hump:

VonSprecken farm, 3 1/2 miles s.e. of Oxford Jct. in Jones Co., looking north

The VonSpreckens have an impressive rock collection around their farmhouse. It includes the two below which were from the nearby Wapsi River and could still be glacial erratics, and two that are not erratics but are native Iowan and beautiful:

Rounded “river rocks” at VonSprecken’s

Probably shale

 

 

 

 

Quartz rock,

VonSprecken ‘s

 

 

 

I wish I was a little rock
A-sittin’ on a hill,
Doin’ nothin’ all the day
But just a-sittin’ still.
I wouldn’t eat, I wouldn’t sleep,
I wouldn’t even wash,
I’d just sit still a thousand years
and rest myself, b’gosh!

 

Scott Andresen’s farm, first farm no. of O. Jct. on Hwy 136, Jones Co.. Rock in center

James Murray’s farm, 1684 50th St., Oxford Jct., Jones Co. The rock is abt. 4 ft. high.

Owner unknown. 1/8 mile south of Hwy 136 & 1/2 mi. east of road between Jones & Clinton counties.

From the book This Is The Place — Iowa: “The first glacier, called Nebraskan, covered all of Iowa and extended as far south as the Ohio and Missouri rivers. It brought a deep layer of drift soil. (Drift soil was made by the ice sheet, and included the sand and gravel washed into the valleys by the streams.) Hundreds of thousands of years passed. The Nebraskan glacier melted and the rich drift soil produced plentiful amounts of food….. “

An Iowa farmer told me a method for breaking a big rock: Make a ribbon of sulfur and molasses on the rock where you want it to break. Set it on fire and as soon as it burns out, when it is still the hottest, drip (or pour?) cold water on the ribbon. The rock will split.

Jim Murray of Oxford Township showed me “glacial till”, a thin layer of loose debris (pebbles and soil) in the otherwise “normal” dark soil, this sample reddish in color. Jim and others who let me photograph their rocks were hospitable and helpful. Thanks to all of them. The information for this essay came from many sources. A particularly rich one was the Iowa Geological Survey website, http://www.igsb.uiowa.edu
Should you drive to see the rocks I’ve described, please remember not to trespass. Ask permission to enter private property.

Glacial rocks are popular as decorating elements. An example is the one below on Hwy 136, north of Oxford Jct. and just south of 60th St. (Slouha road), on a farm owned by Ron Nowachek. Jones County.


Glacial rocks were used as survey markers. This one at Allen Hronik’s lane on Massillon Rd, the first farm southeast of Oxford Mills, was believed to be a section marker. While the section line isn’t at that corner, the rock lies 1/4 mile north of a section line, marking the standard 40 acre measure. Allen said there is another working rock on his farm. He was told by a firm in Anamosa that they know where all the rocks are and still use them for surveying. Allen believes that they are granite and may have come from the west by rail.


The “pointed rock” referenced in an 1832 survey is/was probably marking the southeast corner of section 1 of Massillon Twp., Cedar County. This is how it looked in 2009 on the farm of Allen Cook, 66 Rd Y24, Massillon.

End.                            Judy Nelson, December 2009

Found another in Oxford Twp. in 2010!  Owners do not want the location published.  It is approx. 8 X 14:


Photo’d in 2011:

At a secret location, southwest of Oxford Mills, is this glacial rock.  I hope to take better photos when the weeds die. It is at least 10 feet high and 12 feet wide.  No attempt to move it has been made.

 

At Clarence IA in Cedar County, south of Jones, this glacial rock lays on private property.  Attempts to pull it out of the ground failed but there are plans to try again, then have an image imprinted on the granite rock for use as a monument in Clarence.