Geology and Geography of Arkansas

The geography of Arkansas is both rich and diverse with mountains, river valleys, delta farm land, forests, swamps, lakes, rivers, and bayous.

The state is divided into different destination regions for tourism purposes, but from a scientific point of view there are considered to be 6 natural geographic regions in Arkansas. These are:

• The Ozark Plateau
• The Arkansas River Valley
• The Ouachita Mountains
• The Gulf Coastal Plain
• The Mississippi Alluvial Plain
• Crowley’s Ridge.

These natural systems are divided by things like geology, climate, general plant communities, animals, soil, and land use.

Here is some basic information about the geography of Arkansas and the natural systems of the state.

For tourism purposes the state is divided into regions by location. We have another post about the destination areas of Arkansas if you want to learn more about that.

Geography of Arkansas

The Ozark Plateau

Northwest Arkansas contains the southern section of the Ozark Mountains. This area has flat topped mountains with steep sides and rocky valleys.

As you learn about the geography of Arkansas you might wonder why this mountainous area is called a plateau. This is because, in geological terms, the Ozark Mountains aren’t actually mountains. The deep valleys of the Ozarks were actually caused by erosion and the tops of the “mountains” are not only flat but approximately all the same height.

The Ozarks region of Arkansas is gorgeous with dense forests, stone crags, tall bluffs, stunning overlooks, clear springs, deep hollows, and running rivers.

However it was also a difficult region to farm and settle.

Even early native people tended to view the Ozarks as primarily their hunting territory. There were not many established native settlements here.

Hunting bands often found shelter in the many bluff caves that exist in the region. In fact, artifacts and petroglyphs can still be found in many of the overhanging bluffs in this area.

Later settlers were mostly “Americans” meaning they were second or third generation American-born people of northern European descent.

Settlers barely eked out a living in this heavily forested, steep, and rocky land. Cash crops were not very practical so settlers often turned their crops into moonshine and other products to make a living.

They hunted for meat, but were typically only able to farm enough food for subsistence for their own families.

The farms were far apart which resulted in an isolated way of life. These so called “hillbillies” of the past were characterized by a fierce independence, suspicion of strangers, resistance to authority, and a unique type of mountain music.

Today, those “difficult to farm” rocky hills and dense forests are attracting tourists, retirees, adventurers, and anyone who loves the outdoors.

One of the main tourist attractions in the Ozark Mountains of Arkansas is the Buffalo National River. The river flows freely for 135 miles and is one of the few remaining un-dammed rivers in the lower 48 states. It is a popular place for kayaking, camping, and hiking.

In addition to tourism some of the largest companies in the US are located in the Ozark Plateau. Huge companies such as Walmart, JB Hunt, Tyson and others got their start here.

The quickly growing city corridor of Fayetteville, Bentonville, Springdale, and Rogers is located in the Ozarks Plateau as well as smaller tourist friendly towns like Eureka Springs, Ponca, and Mountain Home.

The Arkansas River Valley

The Arkansas River Valley lies between the Ozark Mountains and the Ouachita Mountains. The geography of Arkansas in this region includes the fertile farmland alongside the river as well as a 40 mile wide swath of low rolling hills between the two mountain ranges.

Besides farmland, coal and natural gas resources are also found in this area.

Because this area is called a “valley” you might be surprised to learn that there are also mountains here. In fact, the highest peak in the state, Mount Magazine, is not found in the Ozark or Ouachita Mountains but in the Arkansas River Valley!

Mount Nebo, Petit Jean Mountain, and Mount Magazine together comprise the Tri-Peaks. These three mountains are flat topped mesas that rise steeply from the flat river valley land below.

All three mountains are now state parks and are very popular places for camping, hiking, and other forms of recreation.

The Arkansas River provided the earliest form of transportation within the state. People came through this area first by boats and then by stagecoach. With the advent of the steamboat farmers were able to transport their crops. At this point the small family farms began to consolidate into larger plots.

Some farmers even began to grow crops like tobacco and grapes for wine. Yes, there are wineries in this area which is unusual in such a warm climate.

Farming is still an important part of the economy of the Arkansas River Valley.

Small towns first began to develop along the river and then the stage line. Today, Interstate 40 runs through the valley connecting the cities of Ft. Smith, Clarksville, Ozark, Russellville, Morrilton, Conway, and Little Rock.

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The Ouachita Mountains

The two mountain systems in the geography of Arkansas are the Ouachitas and the Ozarks.

However, these two natural systems have very different geological histories. The Ouachita Mountains are more like wrinkles in the earth where tectonic plates were pushed together raising up the land. The Ozarks were carved by erosion.

This means that the Ouachitas are less flat topped than the Ozarks. The Ouachita Mountains tend to be long narrow ridges that run from east to west.

Even the soil is different. The Ouachitas are made up of sandstone and shale while the Ozarks are mostly limestone and dolomite.

In addition, the valleys in the Ouachitas are wider than those in the Ozarks with deeper and richer soil and more sunlight which meant that the land was much better for farming both by the original native people who lived in communities here and by later settlers.

This combination of more sunlight and sandy soil means that the Ouachita Mountains have the right conditions for more pine forests while the Ozarks have more hardwoods.

Where rocks are exposed in the two mountain ranges you can see that the Ozarks will typically have horizontal layers while in the Ouachitas the layers are slanted. Sometimes the rocks in the Ouachita mountains are so sharply slanted as to appear almost vertical.

Yes, there were definitely some aggressive geological processes that went on in this area many eons ago!

That same pressure that caused the cracked and sharply tilted mountains Ouachita Mountains also had a hand in creating some of the most fascinating geological phenomena in this area: the presence of hot springs, quartz crystals, and even diamonds.

You might know that the Crater of Diamonds State Park is a place where you can go and dig for actual diamonds and keep whatever you find. But were you aware that it sits in an actual ancient volcanic crater?

Eons ago instability in this same area caused a volcanic eruption that blew an 83-acre crater near the current town of Murfreesboro. This left diamonds near the surface of this soil where they can now occasionally found by visitors to the state park.

Today the Ouachita Mountain region is still important for tourism, timber and agriculture.

The Gulf Coastal Plain

The Gulf Coastal Plain covers most of south Arkansas.

It might seem weird to label a part of the geography of Arkansas as a gulf coastal plain since Arkansas is a landlocked state. However, the Gulf Coastal Plain was once under the sea.

The water was shallow and had beds of mollusks leaving deposits of chalk. You will also find large deposits of sand, gravel, and clay in this area.

We know that after the waters receded dinosaurs roamed the area as their tracks and bones have been found here.

Once humans arrived they began farming this flat to slightly rolling land. The Caddo Indians lived in large farming settlements in this area. The first white settlers had small farms, but eventually there were larger land holders here.

Row crop farming is not nearly as important in this region today as it was in the past. Today, you will find beef, poultry and aquaculture farms in the area. In addition much of it this region is covered with managed pine forest and used for timber.

The main rivers in the Gulf Coastal Plain are the Ouachita, the Red River, and the Saline River. The Ouachita has moved back and forth enough to leave several lakes that are popular fishing sites.

This land also has fossil fuel. Oil was discovered here in the 1920’s. This created a few boom towns such as El Dorado which is still a major headquarters of the Murphy Oil Company.

Historic Washington State Park is a great place to visit in this geographical region of Arkansas in order to learn more about what life was like here in the past.

The Mississippi Alluvial Plain

The Mississippi Alluvial Plain is more commonly known as the Delta. The Arkansas Delta encompasses the eastern part of the state all along the Mississippi River.

Due to its rich and fertile soil this is one the most productive agricultural regions in the world.

This area, like the Gulf Coastal Plain, was once covered by the ocean. As those waters receded they left sand, silt, and gravel and large rivers.

The flooding of the Mississippi River that used to happen regularly in this area deposited dark, rich soil in the Delta. The forest trees, especially Cypress trees, grew to enormous size.

The native residents of the region were known for building mounds many of which can still be seen. They had an extensive culture and traded with other groups. You can see some of the remnants of their culture at the Hampson Archeological State Park located in the historic town of Wilson.

The first white settlement in Arkansas was in the Mississippi Alluvial Plain. It is called the Arkansas Post and the location can seen at the Arkansas Post National Memorial.

As the cotton gin made cotton planting more profitable, large land owners moved in with slaves to tame the wilderness in the Delta and grow cotton. After the Civil War many of the former slaves remained in the area and become sharecroppers.

In addition to forests and farmland there were swamps in this Mississippi Alluvial Plain.

At first the swampland was not considered to be viable for food production. However, in the early 1900’s rice was introduced here and now Arkansas is the top producer of rice in the United States.

Unfortunately, in the early 1900’s the lumber industry also discovered the timberland of the Delta and clear cut entire old growth forests. This combined with the Great Depression and drought led to the suffering and poverty of the Dust Bowl era.

Sadly, about 90% of the forests were cleared and many of the original plants and animals that once thrived in the Delta are gone.

Due to the changing course of the Mississippi River, oxbow lakes are another important part of the character of the Delta. An oxbow lake is formed when a river changes course and leaves behind a bend (or oxbow) filled with water.

The largest oxbow lake in the US is Lake Chicot in the Arkansas Delta.

Today, the Delta is still the heart of Arkansas’ agricultural economy.

Crowley’s Ridge

Crowley’s ridge is the smallest of the natural divisions in Arkansas and one of the most interesting. It is the only division located within another division and is also one of the great geological oddities of the world.

The truth is that geologists don’t really know why Crowley’s Ridge exists.

Perhaps it was formed by a massive change in the Mississippi River, or perhaps it came from the folding of the earth’s crust. It seems that Crowley’s Ridge is still very, very gradually rising.

Crowley’s Ridge is in the Delta region of the state. It runs about 150 miles from southeastern Missouri to the city of Helena-West Helena but is only about half a mile to twenty miles wide.

The top of the ridge is 200 to 250 feet higher than the flat Delta land which surrounds it. The slopes rise sharply making the ridge very visible as you approach through the Mississippi Alluvial Plain.

Even the soil of Crowley’s ridge is different from the rich Delta soil. The ridge is topped with a wind blown dust called loess. This blanket of loess on Crowley’s Ridge is up to 50 feet deep. However it is very fragile.

Loess is highly susceptible to erosion and mud slides and can’t support the type of farming that was used in the Delta land below.

Because the ridge, unlike the rest of the Delta, was not prone to flooding farmers would often build their homes here. It also became the roadway for travelers as it helped them to avoid the mud, floods, and mosquitoes of the Delta.

The cities of Jonesboro, Paragould, Forest City, and Helena-West Helena are part of Crowley’s Ridge.

I hope that you have enjoyed learning more about the geography of Arkansas.

Just so you know…I am not a scientist by any stretch of the imagination, just a researcher who loves my home state of Arkansas.

If you are interesting in learning more about the geography of Arkansas here are some sites you can check out:

• Arkansas Quartz Crystals
• Geology and Geography of Arkansas
• Regions and landforms in Arkansas
• Why are there diamonds in Arkansas
• Arkansas Geological Survey

Thanks for stopping by.