GEOLOGY is a very interesting subject of scientific research. The clues are all over the landscape, in its soil profiles, and in the buried rock layers underlying all of the Midwest and Iowa. Deciphering these clues is part of what geologists do. Geologists have long recognized the value of understanding, or at least trying to understand, how our earth came into being. It is this understanding that helps humans find water, find and use resources that allow us to thrive and survive, find resources to use for construction, and develop our knowledge of methodologies of construction. proper stewardship to conserve soil, air and water. Understanding how our Earth functions and reacts to galactic-sized forces of nature is an important clue in trying to predict events in Earth’s future.
Phil Kerr and I have had several email conversations over the past year. And the virus was planted to return to Marshall County to present an information program on local landforms. Kerr received contact information from the Marshall County Conservation Board to organize a program. I am happy to know that this useful program will help educate all participants about the geological forces that have made Marshall County what it is today. Phil Kerr will explain and provide a brief summary of bedrock and glacial geology. He will also talk about the Iowa River and its history with regards to land forms.
In the current large map of the Midwest, the type of map is referred to as shading. This type of relief representation emphasizes topographic features and elevation differences. It becomes easy to recognize patterns on the earth as if an astronaut in his space station observatory could look at us on a cloudless day to take such a photograph. Well, that’s not how this composite image was created, but you get the idea. This image allows us, and in particular geologists, to tell stories and make interpretations of land forms from a very long time ago.
Note the thick black line that plots and indicates the Last Glacial Maximum (LGM) of the Wisconsin Glacial Episode. Far north of the black line was glacial ice. And this glacial ice covering northern North America stretched from Washington State, Idaho, Montana, the Dakotas, Minnesota, Iowa, Wisconsin and east to ‘northeast to Newfoundland. The name that geologists have given to this ice is the Laurentide ice cap.
In the past 2.9 million years alone, the climate of the northern hemisphere has fluctuated between hot and cold conditions. According to the Wisconsin Geological Natural History Survey, Division of Extension, University of Wisconsin-Madison, these cycles are the result of changes in the shape of Earth’s orbit and the tilt of the Earth’s axis. Colder periods allowed the expansion of glaciers over large segments of the North American continent. And Nick Zentner, a geologist at Central Washington University, notes that over those 2.9 million years, 33 glacial cycles have followed one another, each a little different in duration and flow, and each interglacial warming between advances. ice cream was also not all equal. The point to emphasize is the effect of these advances and retreats of the glacial system that shaped the terrain of North America.
Climate change, all natural, enormous and unstoppable, has followed a steady pattern over the past 700,000 years. Each cycle tends to last around 100,000 years and consisted of a long period of generally cold climate during which glaciers developed, followed by shorter periods of similar or warmer conditions than today. PS. If this is the trend of Earth’s huge natural climate cycles, then why does the mainstream media continue to try to brainwash us today that humans are the cause of climate change? Because they lie to us, ignore the facts, ignore the science, and use disinformation for political power purposes, in false hopes of spending our money somehow on schemes that don’t fit the bill. reality.
The U of Wisc-Madison article continues its analysis of the most recent glacial event. About 100,000 years ago, the climate cooled again and ice spread across the continent. 31,500 years ago, a major advance in ice spread through Wisconsin and continued to expand for 13,500 years before temperatures warmed again. This warming triggered the retreat of the glacial ice (melting faster than any force to advance). A similar story of glacial ice in north-central Iowa can be told from ice originating in Minnesota. And a similar story exists for the James Lobe of Ice in the East Dakota states. Part of where the glacial ice traveled, or where it did not flow, was due to characteristics of the underlying landscape. The highlands diverted the glacial ice into lobes, or tongues or fingers, so that the ice followed paths of least resistance to the lowlands.
The amount of water trapped in the Laurentian ice cap was enormous. As the climate warmed naturally, the ice melted over thousands of years. However, the water has loosened the landscapes of all the territories beneath the once prominent LGM ice. The streams were cut into exposed glacial tills of crushed rock and debris. The valleys were defined by water and these valleys filled with silt, clay, sand and gravel. Tundra-like vegetation eventually took root. And as warmer climates began to dominate, boreal forests flourished, giving way over time to a mix of deciduous trees and, ultimately, grass-dominated landscapes in the Midwest.
On today’s large map, also notice the dark dotted line that crosses eastern Nebraska, northeastern Kansas, Missouri, Illinois, Indiana, and Ohio. This dotted line represents another Ice Age with maximums much older than the Wisconsin system. Geologists call these moments pre-Illinois episodes. Indeed, our landscape has been shaped by past geological events over extremely long periods of time. The red line in eastern Iowa represents an ancient location of part of the Mississippi River. It’s amazing the amount of information that can be discovered from an incredibly detailed map like the one you are looking at today.
And since our human lifespans are very short, where it is easy to ignore the past, it will benefit us to know that Nature reigns. We can only adapt. Geology says that “The present is the key to the past. Let’s learn the facts that made our landscape what it is.
To attend this free geology program, call the Conservation Council office at 641-752-5490 to register. Please do so by September 23 at 4:00 p.m. for the program date of September 28, from 11:30 a.m. to 12:30 p.m. Come see and learn for yourself what geology can tell us. Learn what a geologist sees that we need to know. Appreciate lifelong learning.
Take Home Quote: “People try to do all kinds of smart and different things to improve life instead of doing the simpler thing – refusing to participate in activities that make life bad. ”
– Leo Tolstoy, writer.
Garry Brandenburg is the retired director of the Marshall County Conservation Board. He graduated from Iowa State University with a bachelor’s degree in fish and wildlife biology.
Contact him at:
P.O. Box 96
Albion, IA 50005