“Torn to pieces.” That's how the American frontiersman Davy Crockett, described the West Tennessee landscape nearly 15 years after it was rent asunder by the New Madrid earthquakes that took place from December 1811 to February 1812. The tremors rocked an area that also included the present-day states of Missouri, Arkansas, Kentucky, and Illinois, reshaping not only the landscape but also the lives of the people who settled there.

So why were the quakes all but forgotten by the time of the Civil War? What caused them? And could they happen again?

For this Earth Month episode of Colloquy, we discuss these questions with Dr. Conevery Valencius, author of the recent book The Lost History of the New Madrid Earthquakes. Dr. Valencius is a professor of history at Boston College and has taught at Washington University, Saint Louis, Harvard, and the University of Massachusetts, Boston. She's been a fellow at the Radcliffe Institute for Advanced Study, the National Endowment for the Humanities, and the Dibner Institute for the History of Science and Technology. Dr. Valencius is currently working on a book about earthquakes and the modern energy sector. She received a PhD in the history of science from GSAS in 1998.

This transcript has been edited for clarity.

Paul Massari: Imagine that you and I were standing near the epicenter of one of the New Madrid quakes just as it struck what's now southeast Missouri between December 1811 and February 1812. What would we see? What would we experience?

Dr. Conevery Valencius: Well, we would not be standing for very long. So many of the folks listening to this may well have been in earthquakes at one point or another. And a lot of what people experienced in 1811 and 1812 has a lot in common with what many of us have experienced. The ground shakes. People were thrown to the ground. There was a clattering of objects being thrown off their shelves. People, animals are off-balance.

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At that point in the Mississippi River, animals, birds were hugely noisy; flocks of birds disturbed from their sleep in the middle of the night; cattle, horses letting you know their distress. People saw huge trees being snapped like twigs. The soft, really fertile, unconsolidated sediment—this rich deep soil of the Mississippi flood plain—shook and then drifted like you were shaking some sort of runny egg casserole. Water spread as the earth slumped. This is an area with a high water table. Flooding and water spread, threatening people.

People experienced something that happens in some parts of the world when there are earthquakes, but it happens much more in the Mississippi Valley and that is, if you've ever stood on the edge of a lake or an ocean and put your bare feet on real wet sand, it feels real nice. And if you sort of put your balance back and forth on each foot and squish that sand, the solid earth you'd been walking on, that solid sand starts to squish up through your toes. That's called liquefaction. And it's when you put pressure on the water that's in between all those sand grains until it's the same weight as all the earth pushing down on it. And that happened at very large and very alarming scale because all this loose, unconsolidated sediment—sand from ancient, ancient seas of North America that was under the surface where nobody could see it—liquefied and turned into a fluid.

As the weight of the earth pressed upon [the liquified sediment], it spurted up making this enormous phenomenon that was called sand blows. They looked like sand volcanoes as this white sand from ancient beaches spurted up into the air and then combed over on either side. Sand blows appear in earthquakes in many parts of the world. Usually, they're the size of dinner plates, maybe a platter. In the New Madrid seismic zone, some of them can be up to a kilometer large.

Paul Massari: You mentioned in the book that the Mississippi River actually ran backward at one point. Am I getting that right? How would that even be possible?

Dr. Conevery Valencius: Astoundingly enough, that's true. The earthquakes lifted up many parts of the land, causing a lot of disturbances to water flow, causing small lakes to form, damming up creeks, and so on, creating a whole lake. The earthquake tremors briefly lifted up a portion of the Mississippi Valley itself, the bed of the Mississippi River, causing the current of the Mississippi to run briefly, but dramatically, backward. Soon, the force of all that water eroded the riverbank again. And it started flowing back toward the sea. But it was a fairly dramatic phenomenon. And it's one we've seen recently during Hurricane Katrina. The force of the storm surge was such as to reverse the flow of the Mississippi for a short while. Same thing with Hurricane Isaac about ten years ago and with Hurricane Ida.

People at the time didn't have a lot of geophysical explanations for these things and they didn't understand what was going on. They saw flashing lights in the sky. We're not really sure exactly what's going on with that, although there is a phenomenon of earthquake lights. They heard booming noises. A lot of them reported lightning, which, again, is not what we in our contemporary scientific explanations understand is associated with earthquakes. But it certainly fits the drama of how many people at the time experienced these earthquakes. They smelled sulfur. We would say swamp, gases. People at the time had a pretty clear sense of what was going on when the earth shook and great fissures opened and they smelled sulfur. That was Hell.

So, they experienced things that they didn't know how to categorize, didn't know how to explain, and knew that their explanations of the physical world were only part of what was going on. And many people immediately turned to questioning their relationship with God or with their spiritual forces.

People at the time had a pretty clear sense of what was going on when the earth shook and great fissures opened and they smelled sulfur. That was Hell.

Paul Massari: It was a huge area that felt the impact of these quakes—five states. I think in the book, you describe them as “a hotbed of cultural change and settlement.” What were they like? Who was there? What kind of communities? What were they doing? And what was the impact when the earthquake hit?

Dr. Conevery Valencius: So, the middle Mississippi Valley was a highway of commerce, of gossip, of pathogens, of trade, of diplomacy. People were moving up and down the river and then up that river valley constantly throughout the 18th century and into the early 1800s. This was also an era right at the beginning of the 19th century when the United States is trying to push past its boundaries, trying to claim this land it had bought it on paper anyway from France just a few years before. But militarily, much of that area was still controlled by the major power in the region, the Osage Nation. So, a lot of it was, you know, who was in charge of what? Who would you pay tolls to? Whose permission did you need to seek to cross major river systems? Much of that was in flux.

Americans, along with French and Spanish nationals, along with native peoples of a lot of different nations, were moving into that region, especially peoples of the American Southeast who were trying to get away from the increase of Americans upon their native lands—those who were moving toward this really rich country of the Mississippi floodplain, seeking its fertile farmland, the hunting, the fishing, the natural resources—and saying, “Well, you know, if the Americans are taking over our territory back home, we can make a new place here.” And that characterized a number of Cherokee settlements, as well as Shawnee and Delaware villages right in the area we would now call the epicenter.

Paul Massari: Those indigenous communities were impacted dramatically by these earthquakes. Can you talk about the resettlement that went on for at least some of these people afterward?

Dr. Conevery Valencius: There's a really dramatic impact, especially for some of the very early western Cherokee settlers. There was a thriving Cherokee set of settlements that gets just completely shaken up by these New Madrid earthquakes. What had been fertile farmland becomes swampy morass, becomes an area that is hard to farm and that people don't want to live in anymore.

Those folks move further west into areas that put them squarely into conflict with the ages pushing down from their long-held territory. This is, I think, a very important and really unrecognized moment in some of the political history of the Cherokee people. And it's part of an erasure, really, of native history from both the political and even the geologic history of North America and the United States. You know, if a tree falls in the forest and nobody's there to hear it, what does it matter? And I think one of one of the things that the historic record shows this is there were a lot of people building communities in that area. Most of them weren't Americans and those communities, those native settlements were dramatically disrupted. And it really changed course because of these earthquakes.

Paul Massari: Why did European settlers move in to fill the vacuum left by the indigenous communities that moved on?

Dr. Conevery Valencius: The changes to the level of the land and of the water flow made what had been free-flowing river systems that were good for commerce into real swampy morasses, left other areas covered over with silt and, you know, as newly available for farmland. So, yeah, these earthquakes are part of the story of the many, many factors leading to the U.S. territorial takeover of areas that had been native land.

The fact that this took place among many folks who were mixed race, mixed ethnicity, who were native peoples, who were river travelers, who were basically poor and hardscrabble farmers meant that their records were not accorded much weight in our scientific stories until recently.

Paul Massari: One of the great surprises for me reading this book was the connection between the quakes and American religious life. They strike during the Great Revival, which some people refer to as the Second Great Awakening. So, it's already a period of kind of renewed religious fervor. How did these North American Christians interpret the quakes? What was the role, for instance, of the physical experience, and how they made sense of that in terms of their religious lives?

Dr. Conevery Valencius: One of the things that surprised me was how physical American religion was. When you felt the spirit, when you were receiving a manifestation of God's spirit, when you were manifesting your understanding of God's will in your life, you often did things. You moved. You shouted with joy. You might dance. Many of the backwoods revivalists who were central to this widespread, very powerful part of American Christian revivalism and Christian religion, used or encouraged a kind of physical showing of God's presence. They are in God's spirit with people.

People often talked about God’s spirit feeling like an electric shock. And those are exactly the same ways in which they talked about feeling earthquake shocks—that the jerks and jolts of an earthquake felt to many people like God's spirit speaking to them. And that's how they interpreted it: They felt that God was telling them to get right, to reevaluate their lives, to get in a better relationship with their communities, to be revived.

So, the earthquakes fed into and reinforced the existing revivalism and really reinforced for a lot of Americans a sense that their experience of the world. They might not be particularly educated. They might not be all that literate. But they could have access to what was really important and going on around them.

Paul Massari: One of the other great surprises for me reading your book was that the framework we use to understand earthquakes—plate tectonics—doesn't explain the New Madrid quakes. Why not?

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Dr. Conevery Valencius: If you take your two hands and you put them out flat in front of you and you rub one against the other, and then you kind of put one of your hands a little bit under the other, that is, you know, a pretty rough but reasonable model of plate tectonics, of how these large masses of the Earth's crust bump up against each other and sometimes crumble in underneath or on top of each other. And that explains most of the world's great earthquakes and most of the seismic movement that so many of us feel on the globe today.

But it does not explain why earthquakes would happen in the middle of a tectonic plate, very far from a plate boundary. And that is really mysterious. People working in the geosciences still don't have a complete handle on what is causing the kinds of so-called stable continental region earthquakes that were experienced in the Mississippi Valley.

There are some really puzzling aspects of this. For instance, the earthquakes that were felt in 1811 and 1812 are only the most recent massive earthquakes to have hit the Mississippi Valley back through historic and prehistoric times. Earthquakes hit that region with what looks like fair geologic regularity, on the order of every 500 years, which is a bit unsettling to those of us living in or working in there.

So, we don't have a real clear sense of why that happens or why it appears to be that when the earthquakes hit, they hit in sequences like that of the New Madrid earthquakes of 1811 and 1812, where, rather than building up to one big main shock that then dwindles away with a series of aftershocks, these were three or maybe four, depending on who was counting, major shocks, spaced out with a lot of medium-sized and smaller quakes in between them. And that seems to describe these older paleo quakes as well. Why that is? We still do not totally know.

Paul Massari: The title of your book is The Lost History of the New Madrid Earthquakes and you make the point that 50 years on, they're practically forgotten. How was it that a disaster that was so dramatic and had such a huge impact on the very landscape that people were living on was lost from the collective memory?

Dr. Conevery Valencius: This is really a puzzle to me because I started working on this book mostly out of a sense of intellectual indignation. What were these earthquakes like? I grew up in that region. I thought of myself as knowing something about that place. I'd written a whole other book about that region's history. I had no idea that there were earthquakes of any scale that had occurred. How come not?

Now, the answers have to do with changes to the environment—that the kinds of environmental evidence left by the New Madrid quake are different from those out in hard rock country. This is deep, fertile farmland. The bedrock is far down. They also have to do with changes to the people there, the widespread overlaying of new populations on top of the folks who had been moving into that region. The fact that this early 19th century period is a time of such military and economic tumult meant that there wasn't a lot of passing down of stories.

The chance of having a magnitude of six or greater [earthquake] is estimated to be between 25 percent to 40 percent over the next 50 years. So that's looking like odds that we need to plan for.

But mostly this is a story of the history of science that these earthquakes get testified to in letters and in notes and family Bibles, in newspaper stories with lots of exclamation points. And starting in about the 1880s, very clever scientists and tinkerers around the world started coming up with instruments with which to record the movement of the Earth. And these new machines, these seismometers, began to be the way that those who were interested in the Earth's movement would find out about it. By 1900, to study the movement of the Earth meant to read the readings from a seismograph. Looking through old newspapers, old stories hunters talking about you know the howling of their packs of dogs or the behavior of cattle or disturbed ducks; that wasn't science, that was folktale.

And the people to whom this happened weren't really the people who “counted.” So, the fact that this took place among many folks who were mixed race, mixed ethnicity, who were native peoples, who were river travelers, who were basically poor and hardscrabble farmers meant that their records were not accorded much weight in our scientific stories until recently, where paleoseismologists and multi-disciplinary workers in the Earth sciences have put together those very old, crumbly yellow paper, historical records with evidence from the ground and the environment itself to create a really new story about our geologic history of the middle Mississippi. So, this is a history that has only recently been rediscovered through the work of a lot of the folks in the Earth sciences.

Paul Massari: What was the legacy of this earthquake going into the 19th and 20th centuries? You were talking about this very fertile soil and some parts of the land then getting this silt that makes them available for farming in ways that they weren't before. What was the impact on patterns of settlement and relationships between indigenous communities and indigenous and European settler communities as time went on?

Dr. Conevery Valencius: In the decades after the Civil War, the counties of northeast Arkansas and of southeast Missouri were known to many Black American families as places to be very careful not to go. There were a number of sundown towns, so-called because African-Americans were not welcome after sundown. These were areas in which the peculiar American form of domestic terrorism—the anti-Black violence of the various groups that we now put under the rubric of the KKK—operated with ferocious violence against many of the folks who were moving into that region to farm cotton on that rich soil. And the availability of that farmland—the fact that what had been native land had gotten so swept over by majority-white farmers—that meant that the racial tensions that were ever-present in many parts of the United States and certainly in the cotton-growing countries, came to a real head in exactly this region of what our scientists would think of as a new Madrid seismic zone.

That racial violence became, in a sense, really part of the story that got told, as opposed to older people's stories about an earthquake. So, I think it's a real cautionary tale about what we don't see that might be true in our environments because of our history of American racism.

One of the most poignant sources I read in the story of this book was an expedition sent out by Harvard University to go along the Mississippi River and record the native plants and flora. And the very dry scientific author recorded that some of the material might not have been as carefully recorded as they wanted because it was not safe for many of the Black workers assisting them to go very far. I thought, “Wow. We talk about diversity in the sciences and what that will bring us. We talk about what we don't see.” Right? If we're not engaging the full range of folks who are interested in whatever endeavor we're doing—the arts and the sciences and all aspects of our society—that was a really pointed reminder to me of quite literally what scientific evidence could not be collected because Black workers would not be safe going into certain regions of the New Madrid seismic zone.

Paul Massari: There are a lot more people in Missouri, Arkansas, Tennessee, Kentucky, and Illinois today than there were 210 years ago. What would happen if there was another event like the New Madrid earthquakes? I imagine you've talked to the seismologists and the geologists. How likely is it that these kinds of quakes could occur in that part of the country again?

Dr. Conevery Valencius: The Earth scientists and people who study this have some pretty sobering warnings for us. These earthquakes are estimated to be, you know, maybe around about 7.0 magnitude. And any seismologists listening is going to now have a heart attack because, you know, these magnitudes are really exact and you shouldn't approximate them like that. But that's the best we got.

It now looks like we've got in the next 50 years about a seven to 10 percent probability of having a repeat of events of that magnitude. What's more sobering is that if we look at earthquakes of magnitude six, which, you know, a lot of folks from in what we think of as earthquake zones, like, a lot of Californians would say “Oh well. A six. You know, we can deal with that.” In areas with a lot of loose soil, the shaking spreads much faster, much further, and more easily. Buildings are not all built to code. So the same magnitude of earthquake can have far greater effects. The chance of having a magnitude of six or greater is estimated to be between 25 percent to 40 percent over the next 50 years. So that's looking like odds that we need to plan for.

Now, there are things that people and that communities can do and are doing to plan and prepare for that kind of likelihood along the Mississippi Valley. There are increasing seismic codes for new buildings, especially bridges that are vulnerable. The Great Shakeout is run every October for people to practice what to do in case of an earthquake. You drop, you cover, and you hold on. There are a lot of resources from the U.S. Geological Survey, through our taxpayer-funded federal science, about how to plan for your family, your community, your business, your church, your people that you need to take care of before an earthquake. And it's important that we do so. A 2015 study showed that about 8,000,000 people might be subject to potentially highly damaging ground shaking were earthquakes of the size of the 1811 and 1812 events to recur.

So, these are not theoretical risks and they're not risks that anyone in the mid-continent can dismiss. But much of the kinds of preparation that we do against an earthquake or to prepare for that kind of hazard will also serve us in good stead for other kinds of disasters as well. Some of the kinds of preplanning, family conversations about where to meet or how to get in touch, saving documents, those will also help us with other kinds of natural disasters.

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