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Tuesday, July 16, 2024

This Land is Our Land

From glaciation to a changing river bend, the topography, physiology, and geology in southwestern Indiana is rich to say the least. At surface level it is easy to see why this land is special. But digging further into the underlying levels of bedrock, more and more explanations are revealed to just how unique the area Vanderburgh County occupies is.

Dr. William Elliott, associate professor of geology and chair of the geology and physics department at the University of Southern Indiana, describes topography as how much high elevation or low elevation is in an area.

“Topography is looking at the landscape, the hills, or how flat an area is,” says Elliott.

The physical shape of our area begins with topography, which starts by dividing the land into physiographic provinces. Elliott says the underlying rock, topography, sediments, and types of deposits define these sections. Southwestern Indiana has two provinces — Boonville Hills and the Wabash Lowland.

Boonville Hills makes up most of Vanderburgh, Warrick, Spencer, Pike and Dubois counties. It is characterized by rolling hills, low relief, and exposures of bedrock.

“There are some areas around Evansville where you can see that exposure,” says Elliott. “There are places around USI’s campus where you can see the limestone and sandstone.”

The Wabash Lowland is the area that lies adjacent to the Wabash River Valley. This area covers the northern tip of Vanderburgh, Posey, and Gibson counties. According to the Indiana Geological and Water Survey, this lowland is mostly covered in shale and nonresistant siltstone.

Bedrock and coal
Another way to section our land is by describing the bedrock that lies underneath it. Not only does this bedrock help shape our land, but the various layers also boost our economy.

Elliott says the bedrock is from the Pennsylvanian Age, which is about 300 million years old. The first layer is composed of Inglefield sandstone named after its locality of the town in northern Vanderburgh County.

The second layer is West Franklin limestone, also named after its locality. Limestone is Indiana’s state stone.

“In older areas of town, people used to use limestone blocks to build stone walls to prevent erosion,” says Elliott. “This is important economically, as well, as there used to be a limestone quarry on South Broadway.”

For Indiana, bedrock in the state is split by an axis that runs from Cincinnati to south of Chicago, says state geologist and Indiana Geological and Water Survey Executive Director Todd Thompson. According to Thompson, the rock dips away from this arch to the southwest and northeast.

“This dip is not recognizable to the eye, but can be traced from outcrop to outcrop and between rock cores,” he says. “The dip of the rocks means the age and type of rocks change southwestward away from the arch — along the arch is limestone and shale, then limestone, to interbedded limestone, sandstone, and shale, to mostly sandstone, shale, and coal.”

This means the type of rock most prevalent in Vanderburgh County and southwestern Indiana is a mix of rocks. Near the earth surface, Thompson says the county is home to rocks from siliciclastics (rocks composed of terrigenous material formed by the weathering of pre-existing rocks) such as sandstone, siltstone, and shale. And of course, there is the coal.

Springfield coal is what fuels our coal mining industry. According to the Department of Natural Resources, Indiana is in the top 10 coal producing states. It is estimated the coal industry supports more than 2,500 jobs adding $750 million dollars to the economy. According to the DNR, most of the coal produced in the state is from operations based in southwestern Indiana.

The long history of coal mining also has left several abandoned coal mines throughout the years. The most well known is Reitz Hill where F.J. Reitz High School sits. According to Vanderburgh County Historian Stan Schmitt, this shaft was owned by the Ingle family and is possibly the oldest mine in the state. It began operation in the 1850s.

“There were more coal mines at First Avenue and on Diamond, which is why Diamond Avenue has its name, from the Diamond Coal Mine,” says Schmitt.

Glacial Limits
Although it has been thousands of years ago since glaciers were present, the effects have been long lasting. The glacial effects begin in the far northwest corner of Vanderburgh County. This is the southernmost point of the Illinoisan glaciation line (or Pre-Wisconsin glacial advance) and marks the spot of a glacier more than 18,000 years ago.

The glaciation has an effect on everything, but most importantly it is one of the main reasons our region does so well agriculturally. Land smoothed by the glaciers were left with rich soil the glaciers deposited.

“The Wabash River Valley has a lot of glacial sediments deposited by the ice and melting ice that washed a bunch of sediment down the valley,” says Elliott. “These produce good soils making our area pretty agriculturally successful.”

Not only have the glaciers had an effect on one of our area’s biggest economic industries, it also has had an effect on the physical shape of the land. The East Side of Evansville lacks strong bedrock; when glaciers came through our area it smoothed out the land. The West Side has copious amounts of underlying bedrock and was more resistant to the glaciation effects than the East Side, leaving the West Side with more hills.

The River Bend
According to state geologist Todd Thompson, the Ohio River was formed during the last glaciation of North America — a result of the drainages that flowed north across Indiana being forced southward, ultimately being directed to the Mississippi River.

“Today, the Ohio River meanders in its valley, creating new land in the inside of the meander and eroding its outer bank,” says Thompson.

It is assumed by most people the Ohio River is the dividing line between Indiana and Kentucky. But those living in Evansville and Henderson, Kentucky, realize this is not truly the case. There is one exception to the rule. Better known as the location of Ellis Park, the state line drifts farther north of the Ohio River in one spot.

The explanation is simple — when Indiana was declared a state in 1816 the current state line was where the Ohio River was 200 years ago. According to Elliott, over time as the coursing water flows through river bends, the water on the outside edge slowly pushes the river boundaries forward.

At this spot the river makes a smile shape, and the outside edge takes a dip to the south. Over the years, that dip has gotten more defined pushing the river farther into Kentucky, leaving a small stretch of land just north of the river’s edge.

Pigeon Creek

The Ohio River may get most of the credit for being the biggest waterway that shapes our county; but without Pigeon Creek, things may have been a bit more difficult for the earlier settlers of southern Indiana.

In its entirety, Pigeon Creek runs 47 miles starting at an eastern source in rural Gibson County near Princeton, Indiana, and a western source near Owensville, Indiana. After merging south of Fort Branch, the creek curves into Warrick County before cutting back west into Vanderburgh, trekking through Downtown Evansville before it finally empties into the Ohio.

As a large creek with many tributaries of its own, Pigeon Creek offered a way of accessible travel for settlers, says Vanderburgh County Historian Stan Schmitt. When the Wabash and Erie Canal was constructed in the 1800s, Pigeon Creek became a part of the waterway, allowing flatboats access to the Ohio River near its mouth. Its banks also offered space for Evansville industry to take off.

“Where Stringtown and Pigeon Creek are is where the mills were for years,” says Schmitt.

Today, Pigeon Creek plays into transportation in a different way. With the greenway passage, it offers scenic views for walkers, runners, and bikers.

Southwestern Indiana is close to two seismic zones — the New Madrid and the Wabash Valley. The New Madrid is located in Arkansas, Missouri, and Tennessee and The Wabash Valley zone is in southern Illinois and the Wabash River Valley.

There are no significant fault lines in the Evansville area, but since we are close we could potentially feel the earthquakes,” says Elliott.

The New Madrid fault line is responsible for some of the largest earthquakes in American history known as the “New Madrid earthquakes.” Elliott says the quakes — which occurred in late 1811 and early 1812 — measured 8.1 or 8.2 on the Richter scale, meaning the shaking would have been felt in Evansville.

The most common way to measure an earthquake is the Richter scale, but there is a second way. The Mercalli scale measures human experience. Elliott says the earthquakes in 1811 and 1812 would have been rated a seven on the Mercalli scale. According to this rating, everybody would run outdoors, damage to buildings would vary on quality of construction, and automobile drivers would notice the movement.

“Even if there was an earthquake along the New Madrid fault line, we would experience some shaking in Evansville,” says Elliott. “And if there were an earthquake along the Wabash Valley line, it would ramp it up and people would feel it even more.”

More than 40 earthquakes of a magnitude of 3.0 or greater have affected Indiana, with the largest in the southwestern part of the state, adds Thompson.

“Every couple of years there is a small earthquake that can be felt,” he says. “In the past 25,000 years, there have been eight or more large earthquakes.”

Movers and Shakers: Vanderburgh County does not sit directly on a fault line, but its proximity to the Wabash Valley seismic zone has made the county and its residents subject to some sizable earthquakes over the years. This map of the New Madrid and Wabash Valley seismic zones indicates the magnitudes of earthquakes in the region. Red dots denote magnitudes larger than 2.5 occurring from 1974 to 2002 , while green dots are quakes that occurred prior to 1974.

Into the Woods

Legend has it that before Indiana was settled, a squirrel could travel from Vanderburgh County all the way to Michigan without touching the ground. Today, southern Indiana’s landscape looks a little different, with urbanization and agriculture clearing out a majority of the trees over time.

“In this area in particular, we have a good amount of bottomland forest because of the soil that we have, so it’s much wetter,” says Shelby Hall, natural resources and operations manager at Wesselman Nature Society.

Indiana is home to 101 native trees, and more than 50 of those species can be found in Vanderburgh County. Hall says the county is unique because it is right on the border between being southern and northern.

“We kind of have a mixture of both you wouldn’t think we would have,” she says. “We have both types of hackberries here — northern hackberry and southern hackberry — and the same with red oaks — we have a northern and a southern red oak — which not many places can say they do. We also have bald cypress trees, which often are considered a southern tree. Only a handful of counties in the state have them.”

Wesselman Woods also is a unique part of the county as one of the largest old-growth forests within a city throughout the country, boasting 200 acres of trees that have never been touched or cut down. At Wesselman Woods, pawpaw trees are one of the most common understory species; but throughout Vanderburgh County, other popular species include sweetgums, maples, and tulips (understandably as they are the state tree).

While much of the change to the county’s forest landscape is due to human interference, change also is part of the circle of life. Hall says succession is the term for the change of a forest as one community of tree species replaces another and also is inevitable whether a forest is in the middle of a city or not. Being surrounded by the city of Evansville at Wesselman Woods, they are seeing unpredictable successional changes. She also stresses, however, taking care of the area’s trees and forests still is vital.

“Our volunteer and tree expert Dennis Pepper told me it takes seven trees to produce enough oxygen for one person,” says Hall. “If you think about that, we definitely don’t have that. It’s kind of one of those accountability things. Where are your seven trees? Have you contributed to what’s out there?”

Vanderburgh County, Inc.

Two hundred years ago in southern Indiana, political tensions were high. At that time, Warrick County ran from the Wabash River all the way to Corydon, Indiana, a 120-mile stretch along the Ohio River that today holds seven separate counties.

Hugh McGary Jr. had succeeded in his campaign to make his little town of Evansville the county seat. Then, Posey County was split off of Warrick at Fulton Avenue, leaving Evansville on the western edge of a county spanning almost 100 miles. During this period, Ratliff Boon, the namesake of Boonville, Indiana, was the representative for Warrick County; however, the young, up-and-coming politician Joseph Lane was quickly becoming a threat.

Realizing how large Warrick County was and to ensure all parties remained happy, a deal was struck to split the county into three separate counties — Vanderburgh, Warrick, and Spencer. Ratliff Boon remained the representative for Warrick County with Joseph Lane taking Vanderburgh, which officially was formed on Jan. 7, 1818. With McGary’s championing, Evansville was named the county seat for Vanderburgh. The only other incorporated city in the county was Darmstadt, which still is the case today.

Early into the county’s history, a coal boom throughout southern Indiana proved to be important to the area’s culture, economy, and geography for almost a century. Remnants of the mining industry still are apparent today, from webs of abandoned mines that weave beneath the city to markers like Diamond Avenue named after the Diamond Coal Mining Company.

Even as gasoline and oil were discovered early in the 20th century, the industry found it was cheaper to strip-mine coal in Warrick County than it was to dig 275 feet down in Vanderburgh County. With its prime spot along the Ohio River, the mines were not only supplying coal to the county, but also the steamboats and railroads passing through.

The river was a major factor in McGary’s decision to settle in the area and, along with impacting the economy and industries of the county, it has greatly influenced the shape of the county itself. Today, the U.S. Army Corps of Engineers adjusts the banks of the river to ensure it keeps its shape and to allow barges to pass through the bend. As time flows, however, the river will inevitably continue to move, keeping the area and land dynamic.

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