Discover the Biggest Impact Crater in Ohio – It’s 9 Miles Wide!

Written by Drew Wood
Published: July 28, 2023
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If you’re from the Ohio area, you’ve probably heard of Serpent Mound. It’s an amazing 1,348-foot-long raised mound in the shape of a snake, built by ancient Native Americans. Sites like this had great religious and cultural significance for the people who built them. But why did these ancient people choose this particular building site? As it turns out, the area has fractured and unusual geological formations that were the result of a meteor impact millions of years ago. After such a long time, most traces of the crater were no longer visible. But the Native Americans could tell from the fractured landscape that this was an unusual, special place. Let’s discover more about the biggest impact crater in Ohio, along with Serpent Mound.

View of the great Serpent Mound.

Serpent Mound is the largest serpent effigy in the world.

©Justin Lee DeLong/

Serpent Mound


Serpent Mound is located in Adams County, Ohio, about 64 miles southeast of Cincinnati. Situated on a plateau in Brush Creek Valley, the mound is a 3-foot high, 1,348-foot-long earthen effigy of a snake. The design is sinuous and winding, with a coiled tail. The mouth of the snake holds a hollow 120-foot oval structure that aligns with the summer solstice. Serpent Mound is the largest of its kind in the world. There are also three burial mounds nearby dating between 800 BC and AD 1650. Archaeologists disagree about when ancient people built the mound, but agree it was anytime from 300 BC to about AD 1100.

Serpent Mound Ohio

Serpent Mound is made of piled and compacted earth and stone, on average 3 feet high.

©Seen Unseen Media/


Archaeologists think a supernova that appeared in 1054 and Halley’s Comet in 1066 may have inspired prehistoric Native Americans to build Serpent Mound. It’s possible the long tail of the comet inspired the idea of a snake. Some researchers think the winding shape of the mound aligns with solstices and equinoxes. This would make it useful as a lunar calendar. It may be a depiction of a Native American creation myth about a great serpent. This lord of the underworld impregnated the first human woman. It may have also had ceremonial religious purposes, as many indigenous cultures considered snakes to have supernatural powers.

Halley's Comet, photographed during its last appearance in 1986. Amateur image made using a 35mm SLR camera and film, with a 135mm telephoto lens.

This is Halley’s Comet at its last appearance, in 1986. It’s 1066 visit may have inspired Serpent Mound.

©Brian Donovan/

The Meteor Crater Beneath Serpent Mound

The meteor crater beneath Serpent Mound is known as the Serpent Mound Crater or the Serpent Mound Disturbance. It is located mainly in Adams County, but parts of it extend into Highland County and Pike County. Although it is highly eroded, scientists can tell it is a “complex crater.” This type of crater includes a central uplift, a transition zone, and a ring-shaped trough in the outer part, called a graben.

The crater is absolutely massive, but difficult to distinguish from the surface because it is highly eroded. Geologists research it by collecting and analyzing rocks samples from across the region. It was previously thought to be five miles in diameter, but a 2010 study revealed it is actually closer to an astounding nine miles across! The impact that caused it likely was the result of a comet or meteor that hit Ohio anywhere from 256 and 330 million years ago. The video below describes the Serpent Mound Impact Structure:

How Big was the Explosion that Created the Crater?

Estimating the size of the object that caused the Serpent Mound Crater is difficult. Explosions and the resulting craters can differ greatly in size depending. It depends on factors like the composition of the object, whether it explodes in the air or on the ground, what kind of rock and soil is in that location, and how fast the object is moving. As an example, a meteor 1,640 feet in diameter could cause an 88-megaton explosion. This would leave behind a nine-mile crater such as the one at Serpent Mound. For comparison, the Tsar Bomba, the largest nuclear weapon ever detonated, created a 50-megaton explosion.

If the same explosion happened in the same place today, it would create a fireball five miles wide that would tower into the stratosphere. Everything within a 12-mile radius would sustain heavy to moderate damage. Further out, people up to 38 miles away would get 3rd degree burns. This includes the residents of Chillicothe, a city of 22,000 people to the northeast. The impact of the explosion would cause Earth tremors of 7.4 on the Richter scale as far as 300 miles away. People in Chicago, Chattanooga, and Charlotte would feel it. The air pressure wave would shatter windows as far away as Canada, Oklahoma City, or Jacksonville.

Nuclear Explosion

The explosion that created the biggest impact crater in Ohio would have measured about 88 megatons.

©Romolo Tavani/

What Lived in Ohio at That Time?

What kinds of creatures lived in Ohio around 300 million years ago? This was the Paleozoic Era. North and South America, Europe, and Africa were all joined together in the Pangea supercontinent. Ohio had been below sea level in previous eras but by this point had risen above sea level. Heavy erosion by wind and water took place, removing most of this layer from the geologic record. The time of the dinosaurs, the Mesozoic, is entirely missing from the record.

Because dinosaurs didn’t arrive on the scene until 225 million years ago, they had not yet evolved at the time the Serpent Mound Crater was formed. Life during the Paleozoic was very primitive. It mostly consisted of invertebrates, fish, and amphibians. All the major groups of plants had formed: mosses, liverworts, hornworts, clubmosses, ferns, horsetails, and seed plants.


Trilobites were one of the primitive species that had evolved by the Paleozoic era.


What Wildlife Lives in Ohio Today?

Southern Ohio has a milder climate than the northern part of the state. The hilly landscape is a mixture of forests and farms. It has the common animals found in the Eastern United States, including squirrels, raccoons, opossums, white-tail deer. Some of the notable carnivores are coyotes, bobcats, and the occasional American black bear. The most common bird species are blackbirds, bluebirds, cardinals, chickadees, mourning doves, flycatchers, goldfinches, blue jays, robins, woodpeckers, swallows, and sparrows.

Pair of cardinals perching on a tree branch in the snow

Cardinals are among the most beautiful of Ohio’s plentiful bird species.

© Wang

Could Ohio Get Hit Again?

An asteroid the size of the one that clobbered Ohio hits Earth rarely: only once in tens of millions of years. If one did hit the planet today, it’s most likely it would hit the ocean, as 70% of the Earth’s surface is covered in water. Of the land surface, only 50% is inhabited by a high number of people. The rest includes places like Antarctica, high mountain peaks and plateaus, forbidding deserts, and deep forests. All of these are areas that are very lightly populated or have no human population at all. Altogether, if an asteroid did hit, there’s only a 15% chance it would hit a populated area. In the table below, we’ve compiled a list of 10 causes of death that are much more likely than a meteor. Check it out:

AccidentOdds of Dying
Car crash1 in 101
Surgery complications1 in 798
Alcohol poisoning1 in 1,606
Choking on food1 in 2,745
Sunstroke1 in 6,368
Accidental shooting1 in 7,998
Plane crash1 in 11,756
Bee sting1 in 57,825
Dog attack1 in 69,016
Lightning1 in 138,849
Meteor1 in 250,000

Serpent Mound Crater: Connected to Cosmos

Interestingly, Serpent Mound Crater is greatly connected to the cosmos. Unbeknownst to those who built it, the crater was formed in a continent-shaking explosion caused by a massive visitor from space. Eons later, prehistoric Native Americans witnessed impressive celestial events: a supernova and a massive comet. These celestial events inspired ancient people to create a sacred symbol on the site, a symbol connected to the creation of the world and its people. They designed the effigy in such a way as to help them make further observations of the heavenly bodies.

Today, modern astronomers catalog asteroids, comets, and meteors to calculate the odds of one striking the Earth. This scientific study is reassuring to us. Perhaps, similarly, ancient people were reassured after their leaders completed their sacred ceremonies at Serpent Mound, so many generations ago.

Sierra Negra volcano

Astronomers catalog asteroids, meteors, and comets to give warning if one is heading toward Earth.


The photo featured at the top of this post is © solarseven/

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About the Author

Drew Wood is a writer at A-Z Animals focusing on mammals, geography, and world cultures. Drew has worked in research and writing for over 20 years and holds a Masters in Foreign Affairs (1992) and a Doctorate in Religion (2009). A resident of Nebraska, Drew enjoys Brazilian jiu-jitsu, movies, and being an emotional support human to four dogs.

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