Glaciers Shaped the Ohio River

Weak Ice Ages began occurring as early as 5 million years ago.  Gradually, they became more severe.  1.4 million years ago, for the first time, glaciers advanced through valleys incised by the Erigan River drainage.  This river system flowed through the present day sites of the Great Lakes which didn’t exist yet.  The Laurentide ice sheet obliterated the Erigan River system and advanced beyond another major, now extinct, river–the Teays.  The Teays River began in the North Carolina mountains and flowed in a northwesterly direction through what today is Virginia, West Virginia, Ohio, Indiana, and Illinois before emptying into the Mississippi River.  Glaciers formed a dam, blocking the northwesterly flow of the Teays River and creating the massive Lake Tight, a 7000 square mile body of water as deep as 800 feet in some spots.   Lake Tight must have been quite a sight–gray gravel and ice on the northwestern side and green boreal forests of spruce, pine, and northern hardwoods on the southeastern shore.  Many species of fish lived in the water, attracting great flocks of gulls; and it was a summer destination for duck, goose, and swan.  The churning waters spawned big waves like those of an ocean rather than a lake.  Overflow from the lake was captured by a minor tributary of the Cumberland River.  The ice forced the water to erode backward into bedrock, lengthening this tributary. This large creek/small river became the mighty Ohio river.  When the glacier retreated, the ice dam melted, releasing an incredible quantity of water into the Ohio river and incising a deeper valley toward its outlet, the Mississippi River.

The ancient Teays River was  a major regional drainage system during the Pliocene and early Pleistocene.  The advance of glaciers during Pleistocene Ice Ages dammed this river, allowing a minor tributary of the Cumberland River to capture the stream flow.  This small river became the mighty Ohio.

Map of Ohio River drainage. Glaciers pushed the water content of the Teays River south, creating the Ohio River instead.  Formerly, it was a small tributary.

Subsequent glacial advances during Ice Ages over the past 1.4 million years have had a major influence on the shape of the Ohio River.  The southern lobe of the Laurentide ice sheet frequently advanced far enough south to push sediment into the northern part of the Ohio River, damming tributaries and creating an extensive network of lakes.  During glacial maximums there were always a chain of lakes along the Ohio border with West Virginia and Kentucky.  The Illinois Ice Age was 1 of the most severe.  It lasted from ~240,000 BP-~135,000 BP.  The Laurentide ice sheet advanced as far south as northern Kentucky–its greatest extent ever.  This backed up lakes from the present day site of Louisville to the Pennsylvania border, forcing water into the Ohio River headwaters and incising 45 feet of bedrock.

Though the Wisconsin Ice Age (~114,000 BP-~11,000 BP) was not as severe as the previous glacial advance, the Ohio River valley was frequently incised by pulses of glacial meltwater.  A recent study of river sediment found that changes in the Ohio River were closely correlated with global climate change.  Warmer climate phases within the Ice Age were associated with greater incising and erosion, resulting from melting ice and large water discharge.  Colder climate phases and lower water discharge caused greater sediment build-up, known as aggradation.

Today, the Teays River valley is mostly hidden by sediment, but its descendent is clearly visible on maps.  Government officials used the Ohio River as a convenient demarcation to draw up borders between states.  Imagine how different a modern day map of the United States would look, if there had been no Ice Ages, and accordingly, no Ohio River worth noting.

Reference:

Counts, Ronald; et. al.

“Late Quaternary Chronostratigraphic Framework of Terraces and Alluvium along the lower Ohio River, Southwestern Indiana, and Western Kentucky”

Quaternary Science Reviews February 2015

 

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