In three months time, us humans who live in Iowa will be anxiously waiting for a new year with its warmer spring, melting snow, protruding flowers and a re-awakening of nature’s plant life. A new cycle of the seasons awaits us.

Take a closer look at the big map color codes. Beginning in Central Iowa, you see a red “thumb print-like” area.

This illustrates the maximum extent of the Wisconsinan glacial ice that did not go any further south than the Des Moines vicinity. As the ice margins thinned over time (melted), its lateral and end moraines of ice went through pulses of smaller re-advances and lots of stalled out stagnant periods.

Many stagnant times seemed to dominate in eastern North Dakota, South Dakota, Minnesota, Iowa and many places along the Great Lakes states of Illinois, Indiana, Ohio, Pennsylvania, New York. Overall, earth’s naturally rewarming was set in motion even though it took about 18,000 years of retreat to reach where the ice is today.

Ice margins were at the Iowa/Minnesota border about 12,000 years ago, then perhaps 10,000 years ago to expose the land in and near Hudson Bay, Manitoba, Canada. Glacial ice continued to lose the battle of a warming climate.

Ice is water in frozen form, and when it melts, water will flow down the slope, pool and ultimately find outlets leading to streams, then rivers and many times all the way to oceans. If you are an avid fisherman for walleye, northern or smallmouth bass, then you may already know that northern Minnesota and Canadian landscapes are entirely formed and shaped by the cutting, grinding and rock removal of where the interface of glacial ice met the land surfaces.

Every depression in the land surface filled with water. Water locked up in glacial ice came from snowfall events of huge durations of tens to thousands of years, all of it evaporation from ocean water.

Thus, ocean levels at the peak of the Wisconsinan episode were in the range of 300 or more feet lower than today. You can see the old continental shelf shorelines by looking at ocean depth charts. Relatively shallow waters extend a long way away from the present shoreline before the ocean depths take over.

If one considers all rock history records of numerous glacial events worldwide, ocean levels went up and down like a yo-yo in direct response to glacial onsets and glacial demises. That is just how it works.

As land surfaces were exposed after all glacial ice melted, Mother Nature began her experiments of growing plant life on the mixed up glacial till, an undifferentiated pre-soil matrices. Vegetation took root to grow that can be generalized and documented by seeds left

behind, by pollen grains from tundra plants to forest types and ultimately grasses.

The timeline reads like this: in years before present (BP) as determined by Radiocarbon dates, 30,000 to 21,500 BP had Spruce dominated forests, all destroyed by advancing ice fronts. Then from 21,500 – 16,000 BP open tundra existed along ice margins.

Looking at 16,000 – 10,000 BP, the climate warming is gaining momentum as spruce forests return with the addition of larch and black ash and lots of sedge species, a wetland specialist plant type. At the 10,000 year mark, vegetation changes gave way rapidly to conifer-hardwood forest species mixes.

Time keeps marching so that between 10,000 – 9,000 BP, more warming ensued so that deciduous forests were common with oaks. This suggests a more moderately moist climate, which meant rainfall patterns were affecting and allowing various plant survival.

In fact, at the 9,000 year mark, prairie grasses were common in western Iowa. Then the time frame from 8,500 – 6,500 years before present has soil samples of pollen and seeds radiocarbon dated to show prairie expansion in central Iowa where it dominated best between 8,000 – 3,000 BP.

Forests of Iowa prevailed in eastern Iowa until about 5,400 BP. Prairie dominated during warmer and driest conditions of western and central Iowa. At 5,400 BP, the generalized pattern of mesic weather (moderate moisture) allowed deciduous forest to prevail and thereafter until modern times, some of those forests were replaced by prairie.

When settlers arrived in the Midwest and Iowa, about 85 percent of Iowa was tall grass prairie vegetative land cover. Many forest areas were also cleared for farming. Almost all except one-tenth of one percent of native prairie was converted to cropland.

Wetlands of Iowa pre-settlement are estimated at 1.5 million acres. Today natural wetlands sculpted into the land surface by previous glacial scouring only number collectively at 27,000 acres.

Taking the entire timeline into consideration of climatic and vegetation shifts in Pleistocene and post glacial times, caused adaptations in some cases, extinction in others, of animal life. Animal

fossil evidence tells of tiny air-breathing land snails.

Bigger stock lived here as told by the bones, teeth and tusks of woolly elephants, mastodon and mammoth, as one example. Other critter evidence tells of giant ground sloth, horse, peccary, camel, llama, deer, elk, caribou, reindeer, musk ox, bison, panther-like big cats, wolf, fox, and beaver.

Small rodents were present with hare, vole, shrew and lemming. Each life type existed in an environment of plants filling a large environmental spectrum.

Fossil beetles are documented in the time frame of 16,500 – 21,000 BP in which they had to have lived in tundra conditions. Incidentally for those beetles, tundra air temperatures in July averaged about 11 – 13 C cooler than today.

Humans lived on our landscapes as far back as 10,000 years ago. Back then, the climate was cooler and wetter than what we call normal today.

Clovis spear points were used. Other tools formed from rock types were adapted for skinning and butchering. The Early Archaic period is defined as 7,500 to 5,500 B.C.

As the environmental conditions changed, so did adaptable humans. They hunted bison, elk, deer and increasingly learned which plant foods to eat. Slowly, the nomadic follow the bison type of lifestyle gave way for some native cultures to cultivate and grow sources of food, and thus did not have to travel as far or as often to survive.

Human cultures are also classed as Middle Archaic, 5,500-2,500 B.C. and Late Archaic, 2,500 – 500 B.C. Next is the Woodland traditions from 500 B.C.-A.D. 1,000.

Technologies improved to make pottery, ceramics and practice horticulture. Fishing was a big thing, especially for clams in and along major rivers. Bison and deer were still favored items when available.

Selected grain crops were grown, long before corn and beans became important. Woodland cultures also built effigies, burial mounds, in linear, conical or animal shaped remembrances to past family members.

Effigy mounds of northeast Iowa are well known. Even Hardin County immediately to our north has several documented and preserved effigy mounds on county conservation lands.

I hope you enjoyed this very brief look into the natural history of Iowa, the northern USA and Canada when icy glaciers waxed and waned often.

Winter time for us is just beginning with all of its unpredictability involving cold air, wind and snow. Looking at history tells us of long ago animal and human life that learned to adjust and adapt. Now it is our turn.

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A reminder, Izaak Walton League Christmas Tree sales continue this weekend and next weekend, on Saturdays and Sundays from 10 a.m. to 4 p.m. Each tree costs $50 and is a cut your own experience.

The Ikes grounds is located two miles south of Iowa Avenue on Smith Avenue. Do have a Merry Christmas.

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Charles Dudley Warner said, “The excellence of a gift lies in its appropriateness rather than its value.”

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Garry Brandenburg is the retired director of the Marshall County Conservation Board. He is a graduate of Iowa State University with a BS degree in Fish & Wildlife Biology.

Contact him at:

P.O. Box 96

Albion, IA 50005