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How Glaciers Shaped Indiana
Glacier Terms
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It's hard to imagine that the natural communities found in Indiana were created by a thick sheet of ice. Yet glaciers are responsible for the sandy dunes, the flat prairie land and the rolling hills, that is Indiana.
What are Glaciers?
Glaciers are massive bodies of ice that slowly move across the landscape. They are formed by layers of snow compacted over the years to form a very thick layer of ice. There are two primary types of glaciers: continental and alpine. Continental glaciers are large, dome-shaped sheets of ice and are vastly spread throughout the land. Alpine glaciers are found in mountain regions and in their valleys.
Under the pressure of its own weight and by the force of gravity, glaciers will flow outwards and downwards like a giant frozen river. These massive pieces of ice have a profound effect on the lay of the land as it moves the earth, breaks down rocks and creates hills. Our own landscape was transformed drastically during the last Ice Age. Without this natural phenomenon, Indiana wouldn’t be as unique as it is today.
How Glaciers Shaped Indiana
Around 16,000 years ago Indiana was covered in glaciers. For hundreds of years, the glaciers moved about a foot a day. While moving outward and then retreating back, the glaciers were carving the land. As the ice began to melt, what the glaciers created and left behind dunes, hills, rivers and lakes.
There are basically two types of landscape present in Indiana. In the northern and central parts of the state, the land is flat plains. In the southern region, the landscape is hilly with great stands of forests. It was during the last ice age where these stark differences developed.
Glacial ice extended and retreated several times in the Midwest during the Pleistocene epoch, or the Great Ice Age. Yet every glacier that spread over Indiana never extended past the central region of the state. Once the glaciers melted, the dirt, rocks and sand - or glacial till - that were picked up by the ice were all that was left behind. Any hills or valleys created by previous ice ages were filled with this till and left the land flat. Today this central area is known as Tipton Plain Till. In the northern part of the state, where glaciers retreated more quickly, moraines - or glacial till ridges - were left, but was still left relatively level.
Southern Indiana's landscape greatly differs then the rest of the state. As mentioned before, the glaciers of the last ice age did not extend past central Indiana. Instead, floods from the melted ice carved rivers and the hills that this part of the state is known for. The melted glacier water also created the karst topography by eroding and shaping the limestone bedrock that was left behinds thousands of years ago. That is why our caves, sinkholes and disappearing streams are found only in the southern parts of the state.
Glaciers not only shaped the landscape of Indiana, but encouraged evolution and adaptations in the flora and fauna that exist in Indiana today. Without glaciers, who knows what Indiana’s landscape would be?
For more information on the geology of our great state, check out the Indiana Geological Survey website.
Importance of Glaciers Today
Glaciers are not a thing of the past. Although they do not cover a third of the Earth’s surface as they did almost 16,000 years ago, glaciers can be found all over the world. In fact, they can be found on every continent – though more common in Arctic locations like Alaska and Antarctica.
Today, glaciers cover around 12% of the Earth’s surface and hold almost 75% of our freshwater. According to the National Snow and Ice Data Center, if the glaciers were all to melt, sea levels would rise about 230 feet. Not only would small islands and coastal areas be at risk, but a majority of our freshwater sources would be depleted or lost to salty waters. Since glaciers advance or retreat in response to changes in temperature, they can be sensitive indicators of climate change.
Climate change is a major concern when it comes to glaciers. If the climate continues to warm, then the glaciers will eventually melt away. High greenhouse gas emissions – like carbon dioxide, methane and nitrous oxide – contribute to the overall warming of the climate. These gases are by-products of every day human activities like driving our cars, heating our homes and using electricity produced in coal-burning plants. Deforestation – the mass cutting and burning of forests for agricultural purposes, manufacturing needs or land development – is another cause of global warming because fewer trees means less carbon dioxide conversion to oxygen.
They say that pictures are worth a thousand words. Well, these images may prove just how fact glaciers are melting. In 1940, this photo was taken of the Northwestern Glacier in Kenai Fjords National Park, Alaska.
In 2005, M.F. Bruce visited the Northwestern and captured this photo taken from the same location sixty-five years later.
The differences between these images are staggering. If temperatures continue to rise at the current rate, glaciers will certainly be affected. For example, it has been predicted that all glaciers in Glacier National Park of Montana will have melted away by 2030. Mt. Kilimanjaro, the highest mountain in Africa, has been topped with glaciers for the past 12,000 years. Scientists now believe that the ice cap glaciers will melt entirely by 2020. Therefore it is imperative that we are more aware of global warming and the ways to decrease our emissions of greenhouse gases. Visit the EPA's Climate Control page for tips on What You Can Do.
For More Information on Glaciers
The National Snow and Ice Data Center's All About Glaciers
Indiana Geological Survey's Freeze Frame: The Ice Age in Indiana
and Flat but not Dull: Understanding Central Indiana and Glaciers
NASA's Earth Observatory information on Monitoring Glaciers to Watch Global Change
USGS' Water Science for Schools information on Glaciers and Ice Caps and Water Storage in Ice and Snow
National Snow and Ice Data Center's Education Center and Education Resources
National Center for Atmospheric Research's Where Have All the Glaciers Gone? - educational material.
Indiana State Museum - Indiana's Ice Age Animals - for educators.
Nature picture credits (top to bottom, left to right): Photo © Bruce F. Molnia/Courtesy of the U.S. Geological Survey (Muir Glacier); Photo © Unknown (Northwestern Glacier - before); Photo © Bruce F. Molnia (Northwestern Glacier - after). Last two images courtesy of National Snow and Ice Data Center/World Data Center for Glaciology, Boulder.
