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Earthquake causes fluvial tsunami in Mississippi

Earthquake causes fluvial tsunami in Mississippi

On February 7, 1812, the most violent of a series of earthquakes near Missouri causes a so-called fluvial tsunami in the Mississippi River, actually making the river run backward for several hours. The series of tremors, which took place between December 1811 and March 1812, were the most powerful in the history of the United States.

The unusual seismic activity began at about 2 a.m. on December 16, 1811, when a strong tremor rocked the New Madrid region. The city of New Madrid, located near the Mississippi River in present-day Missouri, had about 1,000 residents at the time, mostly farmers, hunters and fur trappers. At 7:15 a.m., an even more powerful quake erupted, now estimated to have had a magnitude of 8.6. This tremor literally knocked people off their feet and many people experienced nausea from the extensive rolling of the earth. Given that the area was sparsely populated and there weren’t many multi-story structures, the death toll was relatively low. However, the quake did cause landslides that destroyed several communities, including Little Prairie, Missouri.

The earthquake also caused fissures—some as much as several hundred feet long–to open on the earth’s surface. Large trees were snapped in two. Sulfur leaked out from underground pockets and river banks vanished, flooding thousands of acres of forests. On January 23, 1812, an estimated 8.4-magnitude quake struck in nearly the same location, causing disastrous effects. Reportedly, the president’s wife, Dolley Madison, was awoken by the tremor in Washington, D.C. Fortunately, the death toll was smaller, as most of the survivors of the first earthquake were now living in tents, in which they could not be crushed.

The strongest of the tremors followed on February 7. This one was estimated at an amazing 8.8-magnitude and was probably one of the strongest quakes in human history. Church bells rang in Boston, thousands of miles away, from the shaking. Brick walls were toppled in Cincinnati. In the Mississippi River, water turned brown and whirlpools developed suddenly from the depressions created in the riverbed. Waterfalls were created in an instant; in one report, 30 boats were helplessly thrown over falls, killing the people on board. Many of the small islands in the middle of the river, often used as bases by river pirates, permanently disappeared. Large lakes, such as Reelfoot Lake in Tennessee and Big Lake at the Arkansas-Missouri border, were created by the earthquake as river water poured into new depressions.

This series of large earthquakes ended in March, although there were aftershocks for a few more years. In all, it is believed that approximately 1,000 people died because of the earthquakes, though an accurate count is difficult to determine because of a lack of an accurate record of the Native American population in the area at the time.


The infamous New Madrid Fault will take out 150 miles of the Midwest and will end up more devastating than the San Andreas Big One which is also overdue!

Way back in 1811 and 1812, a series of over 1,000 earthquakes rocked the Mississippi River between St. Louis and Memphis. One was so powerful that it caused the river to run backwards for a few hours.

Today, scientists say that the 150-mile-long New Madrid Seismic Zone has a terrifying 40% chance to blast in the next few decades, impacting 7 states – Illinois, Indiana, Missouri, Arkansas, Kentucky, Tennessee and Mississippi – with 715,000 buildings damaged and 2.6 millions of people left without power.

This map shows earthquakes (circles) of the New Madrid and Wabash Valley seismic zones (orange patches). Red circles indicate earthquakes that occurred from 1974 to 2002 with magnitudes larger than 2.5 located using modern instruments (University of Memphis). Green circles denote earthquakes that occurred prior to 1974 (USGS Professional Paper 1527). Larger earthquakes are represented by larger circles. via USGS

We all know the terrifying power of the San Andreas fault. But there’s a fault in the Midwest that packs an even greater punch.

The New Madrid Seismic Zone, sometimes called the New Madrid Fault Line, is a major active seismic zone in the southern and midwestern United States. As shown in the map above, it stretches to the southwest from New Madrid, Missouri.

Earthquakes that occur in the New Madrid Seismic Zone potentially threaten parts of 8 US states: Illinois, Indiana, Missouri, Akansas, Kentucky, Tennessee, Oklahoma, Mississippi.


The Day The Mississippi River Ran Backward—and How It Led to The Trail Of Tears

New Madrid seismic zone. Red circles identify earthquakes that occurred between 1974 and 2002 with magnitudes 2.5 and larger. Green circles denote earthquakes that occurred before 1974. The larger the circle, the larger the earthquake. Source: USGS

In 1811 and 1812, a series of earthquakes emanated from New Madrid, Missouri, and were felt as far away as Ohio and South Carolina. The soil beneath the Mississippi River rose, temporarily changing its course so that it flowed backward. (The phenomenon is not as rare as you might think in fact, the Mississippi flowed backward earlier this year thanks to Hurricane Isaac.) The event might have gone relatively unnoticed except that a group of Muskogee people thought the phenomenon was a river god, the Tie Snake, writhing under the ground.

The Tie Snake was believed to be an antlered river monster who lurked beneath the water and straddled the divide between the Upper and Lower Worlds—between sky and river, and order and chaos. Muskogee culture focused on communal prosperity, but their traditions had been altered by the infiltration of European trade goods and the new culture that accompanied them. Some Muskogee people believed that the Tie Snake was calling them to return to a traditional lifestyle—and warning them to stop the Europeans from infiltrating their culture.

This command might also have gone (relatively) unnoticed, except that a remnant of the Spanish government met some Muskogee warriors in Pensacola, Florida, and gave them weapons. The British had the young American navy tied up off the Atlantic coast in the War of 1812, and the Spanish hoped that the Muskogee men could weaken the Americans from another direction.

The Muskogee (Creek) War

The Muskogees themselves were divided over the potential for conflict, but before they could reach a consensus, European settlers in the area caught wind of the exchange and ambushed the Muskogee warriors at the Battle of Burnt Corn. The Muskogees retaliated at the Battle of Fort Mims in 1813, and panic flared all the way from the frontier outpost to the paved streets of the new capital. Andrew Jackson charged south, leading a cavalry which chased the Muskogees from the Battle of Talladega to the slaughter at Horseshoe Bend in 1814.

The Muskogees were forced to cede a huge portion of their land in the subsequent peace treaty, and Jackson didn’t forget the experience. When he ascended to the presidency, his harsh policies led to the Indian Removal Act of 1830. Throughout the next decade, thousands of Muskogee, Cherokee, Choctaw, Seminole, and Chickasaw people were forced to march from the forests of the Deep South to what is now eastern Oklahoma. The Cherokee people’s journey was the most notorious of the 15,000 who began the journey, 4000 died along the way.

All told, 46,000 Native Americans were removed from their ancestral lands during the forced migrations, in the exodus now remembered as the Trail of Tears.

Laura Steadham Smith is a graduate student at Florida State University.


Hurricane Laura reportedly caused the Mississippi River to flow backward

United Cajun Navy responds to victims of Hurricane Laura

Laura roared ashore as a category 4 hurricane Todd Terrell, president of the United Cajun Navy, joins Neil Cavuto with insight on 'Your World.'

Hurricane Laura has weakened to a depression, but not before causing the Mighty Mississippi River to flow backward in Louisiana earlier this week, according to a report.

Chris Dier posted on Twitter a video of the unique occurrence, which happened around 4 p.m. Wednesday in Arabi, a suburb of New Orleans.

"Hurricane Laura is forcing the Mississippi to follow north instead of south," he wrote. "Barges are now having to fight these tides as they go downriver. Surreal."

The storm was located about 155 miles south of Lake Charles, La., around 4 p.m. CT Wednesday with maximum sustained winds of 145 mph, according to the National Weather Service (NWS). It failed to hit New Orleans directly later but still appeared to cause the unlikely phenomenon.

John Lewis, a research associate professor at the Tulane ByWater Institute, responded to the post, saying the top of the river likely got pushed by the wind -- because the surge impacts were not severe enough to cause a reversal of flow.

This GOES-16 GeoColor satellite image taken Wednesday, Aug. 26, 2020, at 2:40 p.m. EDT., and provided by NOAA, shows Hurricane Laura over the Gulf of Mexico. (NOAA via AP)

He said his understanding was that: "storm surge slows the rate at which the river drains, so the increase in depth is sourced from water flowing from upriver, which then slows and starts to stack up. But the river is a very powerful force and doesn't 'reverse' fully very easily."

Louisiana Democratic Gov. John Bel Edwards told Fox News' "Your World" on Wednesday that Hurricane Laura was potentially the strongest storm to hit the southwestern part of the state in more than six decades.

"Things are very, very serious," Edwards told host Neil Cavuto. "We have a storm that’s a Category 4. It’s going to make landfall just after midnight. It continues to grow in size and intensity and quite frankly the storm surge is going to be a huge threat to life and, in fact, the National Weather Service took the unprecedented step of saying the storm surge is going to be unsurvivable."

The Mississippi River also flowed backward during Hurricane Katrina in 2005 and Hurricane Isaac in 2012, WLBT-TV of Jackson, Miss., reported.


Earthquake causes fluvial tsunami in Mississippi - Feb 07, 1812 - HISTORY.com

TSgt Joe C.

On this day in 1812, the most violent of a series of earthquakes near Missouri causes a so-called fluvial tsunami in the Mississippi River, actually making the river run backward for several hours. The series of tremors, which took place between December 1811 and March 1812, were the most powerful in the history of the United States.

The unusual seismic activity began at about 2 a.m. on December 16, 1811, when a strong tremor rocked the New Madrid region. The city of New Madrid, located near the Mississippi River in present-day Arkansas, had about 1,000 residents at the time, mostly farmers, hunters and fur trappers. At 7:15 a.m., an even more powerful quake erupted, now estimated to have had a magnitude of 8.6. This tremor literally knocked people off their feet and many people experienced nausea from the extensive rolling of the earth. Given that the area was sparsely populated and there weren’t many multi-story structures, the death toll was relatively low. However, the quake did cause landslides that destroyed several communities, including Little Prairie, Missouri.

The earthquake also caused fissures–some as much as several hundred feet long–to open on the earth’s surface. Large trees were snapped in two. Sulfur leaked out from underground pockets and river banks vanished, flooding thousands of acres of forests. On January 23, 1812, an estimated 8.4-magnitude quake struck in nearly the same location, causing disastrous effects. Reportedly, the president’s wife, Dolley Madison, was awoken by the tremor in Washington, D.C. Fortunately, the death toll was smaller, as most of the survivors of the first earthquake were now living in tents, in which they could not be crushed.

The strongest of the tremors followed on February 7. This one was estimated at an amazing 8.8-magnitude and was probably one of the strongest quakes in human history. Church bells rang in Boston, thousands of miles away, from the shaking. Brick walls were toppled in Cincinnati. In the Mississippi River, water turned brown and whirlpools developed suddenly from the depressions created in the riverbed. Waterfalls were created in an instant in one report, 30 boats were helplessly thrown over falls, killing the people on board. Many of the small islands in the middle of the river, often used as bases by river pirates, permanently disappeared. Large lakes, such as Reelfoot Lake in Tennessee and Big Lake at the Arkansas-Missouri border, were created by the earthquake as river water poured into new depressions.

This series of large earthquakes ended in March, although there were aftershocks for a few more years. In all, it is believed that approximately 1,000 people died because of the earthquakes, though an accurate count is difficult to determine because of a lack of an accurate record of the Native American population in the area at the time.


What is it about an earthquake that causes a tsunami?

Although earthquake magnitude is one factor that affects tsunami generation, there are other important factors to consider. The earthquake must be a shallow marine event that displaces the seafloor. Thrust earthquakes (as opposed to strike slip) are far more likely to generate tsunamis, but small tsunamis have occurred in a few cases from large (i.e., > M8) strike-slip earthquakes.

Note the following general guidelines based on historical observations and in accordance with procedures of the Pacific Tsunami Warning Center.

Magnitudes below 6.5

Earthquakes of this magnitude are very unlikely to trigger a tsunami.

Magnitudes between 6.5 and 7.5

Earthquakes of this size do not usually produce destructive tsunamis. However, small sea level changes might be observed in the vicinity of the epicenter. Tsunamis capable of producing damage or casualties are rare in this magnitude range but have occurred due to secondary effects such as landslides or submarine slumps.

Magnitudes between 7.6 and 7.8

Earthquakes of this size might produce destructive tsunamis, especially near the epicenter. At greater distances, small sea level changes might be observed. Tsunamis capable of producing damage at great distances are rare in the magnitude range.

Magnitude 7.9 and greater

Destructive local tsunamis are possible near the epicenter, and significant sea level changes and damage might occur in a broader region. Note that with a magnitude 9.0 earthquake, there is a possibility of an aftershock of magnitude 7.5 or greater.


What is a fluvial tsunami

Many of the small islands in the middle of the river, often used as bases by river pirates, permanently disappeared.

On this day in 1812, the most violent of a series of earthquakes near Missouri causes a so-called fluvial tsunami in the Mississippi River, actually making the river run backward for several hours. However, the quake did cause landslides that destroyed several communities, including Little Prairie, Missouri. Church bells rang in Boston, thousands of miles away, from the shaking.

Tsunamis can travel at speeds of about 500 miles or 805 kilometers an hour, almost as fast as a jet … In all, it is believed that approximately 1,000 people died because of the earthquakes, though an accurate count is difficult to determine because of a lack of an accurate record of the Native American population in the area at the time. Many of the small islands in the middle of the river, often used as bases by river pirates, permanently disappeared. Given that the area was sparsely populated and there weren’t many multi-story structures, the death toll was relatively low. On January 23, 1812, an estimated 8.4-magnitude quake struck in nearly the same location, causing disastrous effects. Sulfur leaked out from underground pockets and river banks vanished, flooding thousands of acres of forests. Reportedly, the president’s wife, Dolley Madison, was awoken by the tremor in Washington, D.C. Fortunately, the death toll was smaller, as most of the survivors of the first earthquake were now living in tents, in which they could not be crushed. 1812. On this day in 1812, the most violent of a series of earthquakes near Missouri causes a so-called fluvial tsunami in the Mississippi River, actually making the river run backward for several hours. Church bells rang in Boston, thousands of miles away, from the shaking. Sulfur leaked out from underground pockets and river banks vanished, flooding thousands of acres of forests. The strongest of the tremors followed on February 7.

Earthquake causes fluvial tsunami in Mississippi. This tremor literally knocked people off their feet and many people experienced nausea from the extensive rolling of the earth.

The earthquake also caused fissures–some as much as several hundred feet long–to open on the earth’s surface. In all, it is believed that approximately 1,000 people died because of the earthquakes, though an accurate count is difficult to determine because of a lack of an accurate record of the Native American population in the area at the time. 1812. The unusual seismic activity began at about 2 a.m. on December 16, 1811, when a strong tremor rocked the New Madrid region. This series of large earthquakes ended in March, although there were aftershocks for a few more years. At 7:15 a.m., an even more powerful quake erupted, now estimated to have had a magnitude of 8.6. On January 23, 1812, an estimated 8.4-magnitude quake struck in nearly the same location, causing disastrous effects. The city of New Madrid, located near the Mississippi River in present-day Arkansas, had about 1,000 residents at the time, mostly farmers, hunters and fur trappers.

This one was estimated at an amazing 8.8-magnitude and was probably one of the strongest quakes in human history.

A normal wind wave travels at about 90kmh, but a tsunami can race across the ocean at an incredible 970kmh! Brick walls were toppled in Cincinnati. How fast is a tsunami? Waterfalls were created in an instant in one report, 30 boats were helplessly thrown over falls, killing the people on board.

from: http://www.history.com/this-day-in-history/earthquake-causes-fluvial-tsunami-in-mississippi, 1812 Fluvial Tsunami along the Mississippi. Brick walls were toppled in Cincinnati. People can see the ocean floor littered with flopping fish and other sea animals. In the Mississippi River, water turned brown and whirlpools developed suddenly from the depressions created in the riverbed. The unusual seismic activity began at about 2 a.m. on December 16, 1811, when a strong tremor rocked the New Madrid region.

The strongest of the tremors followed on February 7. However, the quake did cause landslides that destroyed several communities, including Little Prairie, Missouri. Earthquake causes fluvial tsunami in Mississippi. Large lakes, such as Reelfoot Lake in Tennessee and Big Lake at the Arkansas-Missouri border, were created by the earthquake as river water poured into new depressions. Large trees were snapped in two. Given that the area was sparsely populated and there weren’t many multi-story structures, the death toll was relatively low. Large trees were snapped in two.


Mississippi runs backwards

Lands sunk or were lifted and there were many landslides to go with it as well. The third earthquake, which matched or even exceeded the first in strength, caused a so-called fluvial tsunami in the Mississippi River, forcing it to run backwards for hours.

While most earthquakes take place along the major fault lines of the world that are located at the edges of the tectonic plates making up the Earth’s crust, that isn’t the case with the New Madrid earthquakes. The New Madrid Seismic Zone (NMSZ) lies far from a tectonic plate boundary, but has seen a number of major earthquakes, including events dated around 2350 BC, 900 AD and 1450 AD, apart from the one which took place in 1811-12.


The New Madrid Seismic Zone

When people think of earthquakes in the United States, they tend to think of the west coast. But earthquakes also happen in the eastern and central U.S. Until 2014, when the dramatic increase in earthquake rates gave Oklahoma the number one ranking in the conterminous U.S., the most seismically active area east of the Rocky Mountains was in the Mississippi Valley area known as the New Madrid seismic zone. Since 1974, seismometers, instruments that measure ground shaking, have recorded thousands of small to moderate earthquakes. The faults that produce earthquakes are not easy to see at the surface in the New Madrid region because they are eroded by river processes and deeply buried by river sediment. A map of earthquakes epicenters, however, reflects faulting at depth and shows that the earthquakes define several branches of the New Madrid seismic zone in northeastern Arkansas, southwestern Kentucky, southeastern Missouri, and northwestern Tennessee. Other relatively young faults, which are not necessarily associated with recent earthquakes, or the main seismicity trend in the New Madrid region, are shown in this map. It shows 20 localities where geologists have found and published their findings on faults or evidence of large earthquakes (from sand blows see image to the right).

1811-1812 Earthquakes

In the winter of 1811 and 1812, the New Madrid seismic zone generated a sequence of earthquakes that lasted for several months and included three very large earthquakes estimated to be between magnitude 7 and 8. The three largest 1811-1812 earthquakes destroyed several settlements along the Mississippi River, caused minor structural damage as far away as Cincinnati, Ohio, and St. Louis, Missouri, and were felt as far away as Hartford, Connecticut, Charleston, South Carolina, and New Orleans, Louisiana. In the New Madrid region, the earthquakes dramatically affected the landscape. They caused bank failures along the Mississippi River, landslides along Chickasaw Bluffs in Kentucky and Tennessee, and uplift and subsidence of large tracts of land in the Mississippi River floodplain. One such uplift related to faulting near New Madrid, Missouri, temporarily forced the Mississippi River to flow backwards. In addition, the earthquakes liquefied subsurface sediment over a large area and at great distances resulting in ground fissuring and violent venting of water and sediment. One account of this phenomena stated that the Pemiscot Bayou "blew up for a distance of nearly fifty miles."

After the earthquake [of 1811-1812] moderated in violence, the country exhibited a melancholy aspect of chasms, of sand covering the earth, of trees thrown down, or lying at an angle of forty-five degrees, or split in the middle. The Little Prarie settlement was broken up. The Great Prarie settlement, one of the most flourishing before on the west bank of the Mississippi, was much diminished. New Madrid dwindled to insignificance and decay the people trembling in their miserable hovels at the distant and melancholy rumbling of the approaching shocks.

Woodcut by Henry Howe, from Historical Collections of the Great West (Cincinnati, 1854, p.239). (Public domain.)

The New Madrid seismic zone is located in the northern part of what has been called the Mississippi embayment. The Mississippi embayment is a broad trough filled with marine sedimentary rocks about 50-100 millions years old and river sediments less than 5 millions years old. The upper 30 meters of sediment within the embayment includes sand, silt, and clay deposited by the Mississippi, Ohio, St. Francis, and White Rivers and their tributaries over the past 60,000 years. Wisconsin valley train deposits formed during the glacial period from 10,000-60,000 years ago, and the Holocene meander belt deposits were laid down during the past 10,000 years.

The Mississippi embayment is underlain by Paleozoic sedimentary rocks up to 570 millions years old. The Paleozoic rocks are underlain by even older rocks that appear to have been deformed about 600 million years ago when the North American continent almost broke apart. During the process of continental rifting, a deep valley formed that is bounded by faults and known as the Reelfoot rift. The Reelfoot rift is identified today as a subsurface system of fractures and faults in the earth's crust. New Madrid seismicity is spatially associated with the Reelfoot rift and may be produced by movement on old faults in response to compressive stress related to plate motions.

Geologic and seismotectonic model of the New Madrid region (modified from Braile et. al., 1984).(Public domain.)

Liquefaction

The most obvious effects of the 1811-1812 earthquakes are the large sandy deposits, known as sand blows, resulting from eruption of water and sand to the ground surface. This phenomenon called earthquake-induced liquefaction is the process by which water-saturated, sandy sediment temporarily loses its strength due to the buildup of water pressure in the pores between sand grains as seismic waves pass through the sediment. If the pore-water pressure increases to the point that it equals the weight of the overlying soil, the sediment liquefies and behaves as a fluid. The resulting slurry of water and sediment tends to flow towards the ground surface along cracks and other weaknesses. Overlying soil "floating" on liquefied sediments moves down even gentle slopes, causing fissuring and lateral and vertical displacements. This type of landslide known as lateral spreading is commonly responsible for damage to infrastructure (bridges, roads, buildings) during major earthquakes.

During the 1811 and 1812 earthquakes, liquefaction and resulting lateral spreading was severe and widespread. Sand blows formed over an extremely large area about 10,400 square kilometers. Effects of liquefaction extended about 200 km northeast of the New Madrid seismic zone in White County, Illinois, 240 km to the north-northwest near St. Louis, Missouri, and 250 km to the south near the mouth of the Arkansas River. In the New Madrid region, sand blows can still be seen on the surface today. In the past, the sand blows were attributed to the 1811-1812 earthquakes. We now know that some of the sand blows pre-date 1811 and formed as the result of prehistoric New Madrid earthquakes.

Photograph and schematic cross-section illustrating earthquake-induced liquefaction and formation of sand dikes and sand blows. The photo was taken on February 14, 2016 after the Christchurch, New Zealand earthquake. (modified from the original) (Credit: Martin Luff. Public domain.)

In the New Madrid seismic zone, many sand blows appear as light-colored sandy patches in plowed fields. Flood deposits bury other sand blows. Viewed from above, sand blow have circular, elliptical, and linear shapes and can range up to tens of meters in width and hundreds of meters in length. Viewed in cross-section or in excavations and riverbanks, sand blows commonly take the form of large lenses 1 to 2 m in thickness. Sand blows composed of several layers that fine upward from coarse sand to silt and capped by clay probably formed as a result of multiple earthquakes. Sand blows usually contain clasts, pieces of underlying deposits and soil horizons ripped from the dike walls as the liquefied sand erupted to the surface.

Archaeology

The lower Mississippi River Valley was a fertile homeland to Native Americans from about 9500 B.C. to 1670 A.D. The presence of Native Americans is still evident today in the occasional mound not yet destroyed by modern agricultural practices and the abundant potsherds, lithic tools and points, and bone fragments found in plowed fields and river and ditch cutbanks. Most artifacts encountered during studies of New Madrid sand blows are from the Woodland and Mississippian cultures, which thrived from about 200 B.C. to 1000 A.D. and 800 to 1670 A.D., respectively. Both cultural periods are subdivided into early, middle, and late intervals. Woodland ceramics are characterized by grog (ground up potsherds or fired clay) and sand tempering whereas, Mississippian ceramics are characterized by shell tempering.

Aerial photograph showing light-colored patches that are sand blow deposits near Lepanto, Arkansas (from U.S. Department of Agriculture, January 26, 1964). Many sand blows formed above scroll bars of Pemiscot Bayou, also known as Left Hand Chute of Little River.n (Public domain.)

Photograph of some diagnostic artifact types in New Madrid region: 1, Campbell Appliqué 2, Bell Plain 3, Nodena Elliptical point 4, Nodena Banks variety point 5, Parkin Punctate 6, Madison point 7, Varney Red Filmed 8, Barnes Cord Marked 9, daub with wattle impression. (Photo by Martitia Tuttle, NEHRP-funded research. Public domain.)

Although there are uncertainties regarding their age ranges, certain pottery and point types, as well as plant remains, are considered diagnostic of various cultural periods. For example, Bell Plain, Campbell Appliqué, and Parkin Punctate pottery and Nodena points are diagnostic of the Late Mississippian period Old Town Red pottery and Madison points are diagnostic of the Middle Mississippian period Varney Red Filmed pottery is diagnostic of the Early Mississippian period and Barnes pottery and Table Rock stemmed points are diagnostic of the Late Woodland period. Zea maize, or corn, became dominant in the Native American diet about 1000 to 1050 A.D. and is as an important temporal marker in the region.

Archaeology has played an important role in recognizing and dating prehistoric earthquake-induced liquefaction features in the New Madrid region. Sand blows found below Native American mounds and occupation horizons no doubt formed prior to 1811 because few Native Americans lived in the area after the 17th Century. Diagnostic artifacts found in association with sand blows provide a preliminary estimate of the age of the causative earthquake. Detailed investigations can further constrain the age of the event. For example, artifacts in an occupation horizon buried by a sand blow can provide an estimate of the maximum age of the liquefaction feature whereas, artifacts in an horizon developed in the top of a sand blow can provide an estimate of its minimum age. Similarly, plant remains and other organics found in cultural horizons can be used to date associated sand blows. Radiocarbon dating of plant remains is the most commonly used dating technique in paleoseismology. It is preferable to have radiocarbon dates from both overlying and underlying horizons to bracket the age of the sand blow.

Paleoseismology

Log of trench wall at Dodd site near Steele, Missouri, where sand blow and two associated sand dikes are exposed. The pre-event ground surface was displaced downward by 70 to 80 cm between the two sand dikes. Late Mississippian ceramic artifacts found above and below sand blow suggest that it formed between 1400 and 1670 A.D. Radiocarbon dating of charcoal in the soil horizon buried by the sand blow indicates that it formed after 1290 A.D. Radiocarbon dating of a corn kernel collected from a wall trench dug into the top of the sand blow indicates that it formed before 1460 A.D. Therefore, the estimated age of the sand blow is 1290-1460 A.D. (Public domain.)

Paleoseismology is the study of the timing, location, and magnitude of prehistoric earthquakes preserved in the geologic record. Knowledge of the pattern of earthquakes in a region and over long periods of time helps to understand the long-term behavior of faults and seismic zones and is used to forecast the future likelihood of damaging earthquakes. In eastern North America, where near-surface faulting is uncommon or difficult to identify, paleoseismology often employs liquefaction features to learn about prehistoric earthquakes. Earthquake-induced liquefaction features are distinctive and form as the result of strong ground shaking.

Liquefaction features include sand blows, dikes, and sills. Sand blows are deposits that form on the ground surface as the result of venting of water and sand. Sand dikes are sediment-filled cracks through which water and sand flowed. Sand sills usually take the form of lenses intruded below clay layers and are connected to sand dikes. Most large earthquakes around the world have induced liquefaction.

Over the past decade, paleoseismic studies have begun to unravel the earthquake history of the New Madrid seismic zone. Studies focusing on earthquake-induced liquefaction features utilized archaeology and radiocarbon dating to estimate the ages of liquefaction features, and thus, the timing of the earthquakes that caused them. In this way, sand blows across the New Madrid region were found to have formed during earthquakes about 1450 A.D., 900 A.D., 300 A.D., and 2350 B.C.

Photograph of sand blow deposit and related feeder dike exposed in excavation. Sand blow buries soil that was at ground surface at time of event. Sand dike fills fissure that formed in soil. For scale, shovel blade is 20 cm wide. (Credit: Martitia Tuttle. Public domain.)

In addition, the size and spatial distributions of historic and sand blows that formed about 1450 A.D. and 900 A.D. were determined to be strikingly similar to each other, suggesting that the prehistoric earthquakes had similar locations and magnitudes to the 1811-1812 earthquakes. Furthermore, sand blows attributed to the 1450 A.D., 900 A.D., and 2350 B.C. earthquakes are composed of multiple, fining upward layers similar in thickness to those that formed in 1811-1812. These observations support the interpretation that the prehistoric events were similar in location and magnitude to the 1811-1812 earthquakes and also suggests that they too were earthquake sequences. Paleoseismic studies concluded that the New Madrid seismic zone generated magnitude 7 to 8 earthquakes about every 500 years during the past 1,200 years.

Photograph of sand dike and sill exposed in drainage ditch in southeastern Missouri. Sand dike intruded weathered sand sill emplaced below weathered clay. Layering within the dike and sill indicate that they formed during two or more events. For scale, knife is 8 cm long. (Credit: Martitia Tuttle. Public domain.)

Earthquake chronology for New Madrid seismic zone from dating and correlation of liquefaction features at sites (listed at top) along NE-SW transect. Some sites show age estimates for more than one feature related to different events (e.g., Eaker 2 and L2). Inferred timing of events is shown with colored bands. (Public domain.)

FAQ for Seismic Hazards in the Central U.S.

What is the estimate of the recurrence interval for 1811-1812 type earthquakes?

Paleoseismic (geologic) studies conducted over the last 20 years have shown that sequences of earthquakes of comparable size to that in 1811-1812 have occurred at least twice before, in approximately 900 and 1450 AD. This implies a recurrence interval of about 500 years.

Given this and other new information, can one estimate the probability of damaging earthquakes in the New Madrid seismic zone?

We have learned a tremendous amount about the New Madrid seismic zone since 1985. One of the things we have learned is that coming up with probabilities is much more difficult than we used to think. If we use the data on historical seismicity combined with the new information on recurrence of large earthquakes, and make the same assumptions that go into the National Seismic Hazard maps, we would estimate a 25-40% chance of a magnitude 6.0 and greater earthquake in the next 50 years and about a 7-10% probability of a repeat of the 1811-1812 earthquakes in the same time period.

However, it is VERY important to note that these estimates alone do not include information about WHERE the earthquakes might occur and therefore what shaking might affect any given location. More useful are the estimates of the likely amount of ground shaking that can be expected, contained in the National Seismic Hazard maps. The ground shaking estimated accounts for both the likely ranges of recurrence intervals and locations.

Does everyone within USGS agree on the cause and effects of a future New Madrid earthquake?

No one knows what causes New Madrid earthquakes. However, there are ideas that are being researched. Although there is great uncertainty regarding the cause of earthquakes, scientists generally do agree on what happens when they do occur, that is, the likely levels of ground shaking associated with the waves earthquakes emit. These levels are reflected in the National Seismic Hazard Maps, which represent the products of a long consensus building process. These maps also account for the uncertainties in our understanding.

Differences of opinion within the research community invariably will arise. Generally these are not critical to people outside the research arena. When they are, the USGS sometimes has held workshops to try to come to a consensus and at other times has announced our own internal consensus. Generally, we have met with the CUSEC State Geologists and been able to come to agreement at least between the State Surveys and the USGS, as well as many other scientists. In most situations, the State Surveys are the ones responsible to the State Governors and the USGS works closely with them.

What is the potential for a large New Madrid earthquake triggering an earthquake in the Wabash Valley?

All we know is that this has not happened in the past few 1811-1812-sized New Madrid earthquake sequences.

After a major earthquake in the New Madrid or Wabash Valley seismic zone, what changes to the landscape would we most likely see?

Deformation of the land surface directly over a fault that moves may manifest as very localized uplift or subsidence, or lateral distortions of up to several meters (for a very large earthquake). Shaking can cause ground failure of various types, including liquefaction and landsliding. These would have significant effect on the landscape in terms of damming streams, spewing sand and mud into fields, and causing areas near bluffs and rivers to slide and form a broken up surface.

Can you explain liquefaction? What conditions would increase or decrease the amount of liquefaction?

Liquefaction occurs when loose, sandy, water saturated soils are strongly shaken. The soils lose their capacity to bear any weight and can flow like a liquid. This process is accompanied by high pore water pressures that can force sand, water, and mud upward, often forming the signature sand blows of the New Madrid seismic zone. Many factors affect how susceptible materials are to liquefaction, but some of the most important requirements are the degree of water saturation, the size of the grains, and how well cemented they are.

After the 1811/1812 earthquakes there were reports that the Mississippi River flowed backward. Can you explain this phenomenon and what is it called?

One of the 1812 earthquakes occurred on a fault that actually crossed the river three times. The uplift along this fault formed a scarp or cliff that caused both a dam and waterfalls at different locations. The damming of the river would have temporarily backed the river up, which may account for the descriptions of the river boat pilots.


The Mississippi River Ran Backward

Damage resulting from the New Madrid earthquakes

Photograph courtesy U.S. Department of the Interior | U.S. Geological Survey.

There was plenty I didn’t know about Missouri before I moved to St. Louis in 2007, but one of the things I did know, or thought I knew, was that the state was the site of the largest continental earthquake in U.S. history—a seismic event more powerful than even the San Francisco earthquake of 1906.

The first in the series of three New Madrid earthquakes occurred 200 years ago today, in the early morning of Dec. 16, 1811, in what was then a sparsely populated town in the Louisiana Territory, now the Missouri Bootheel. The second occurred on Jan. 23, 1812, and the third—believed to be the strongest—on Feb. 7, 1812. Countless major and minor aftershocks followed.

New Madrid’s population in 1811 hovered around 1,000: farmers and fur traders and pioneers, French Creole and Native Americans who used the Mississippi River for commerce and transportation. Accounts from people who experienced the quakes firsthand have a biblical flavor: The land undulated chasms opened and swallowed horses and cows whole the Mississippi ran backward and smoke, sand, and vapor obscured the sun. Because of the Midwest’s comparatively stiff and cold lithosphere, tremors could be felt at a much greater distance than in coastal quakes, giving rise to tales of stopped clocks in Natchez and tinkling chandeliers in Washington, D.C.

So ghastly and spectacular were these details that in 2009, I decided to start writing a novel set in the present day but inspired by the 1811-12 temblors. The only problem, as I discovered while conducting research, is that many of the details might not be true.

Over the years, estimates have placed the 1811-12 quakes’ magnitudes anywhere from under 7.0 to 8.5—an enormous range given that one additional unit of magnitude makes an earthquake 10 times stronger. There now seems to be widespread acceptance that the quakes weren’t stronger than magnitude 8, but beyond that, I’ve heard conflicting figures.

And that’s hardly the only contentious issue surrounding the New Madrid (pronounced MAD-red) Seismic Zone. There’s also the question—significant to those of who live in the area—of whether the fault could still unleash another Big One (or three) or whether it has essentially shut down.

In the past 20 years, GPS equipment monitoring the fault has recorded little of the movement that would be expected if it were still active, as Northwestern geology professor Seth Stein describes in his engrossing 2010 book Disaster Deferred: How New Science Is Changing Our View of Earthquake Hazards in the Midwest.

Photograph courtesy U.S. Department of the Interior | U.S. Geological Survey.

Stein suggests there are financial incentives for engineers and institutions that are government-funded or would otherwise benefit from the cost of retrofitting buildings and pipelines to inflate the threat of future quakes. It’s not that there’s no hazard, according to Stein, but when there’s only so much money to go around, it’s an inappropriate allocation of resources to act as if a big earthquake is as likely in Missouri as in California. The counterargument, put forth by agencies such as FEMA and the U.S. Geological Survey, is that it’s impossible to know, and in the face of uncertainty, cities and individuals ought to prepare. The 1811-12 sequence is believed to have been the third set of quakes to occur in roughly 500-year intervals, and this pattern could indicate that the fault “has several more pops left in it,” as John Vidale, a University of Washington geologist, told me. Earlier this year, Vidale led a team that evaluated multiple studies of the fault.

If those holding opposing viewpoints are unlikely to come to an agreement anytime soon, the public is, in a rather weird way, splitting the difference. People I know aren’t preparing for another major quake in practical ways—holding family earthquake drills or stockpiling emergency supplies—but they’re far from ready to accept that the fault has shut down.

St. Louis is about 170 miles from New Madrid, and logically, those of us within shaking distance of the fault should be relieved by evidence that it no longer poses a threat, but in both media coverage anticipating the 200 th anniversary of 1811 and in conversations I’ve had, it’s clear that people are reluctant to accept that the danger has passed. As a novelist, I can think of reasons why I’d prefer for the fault to still be active, just as I’d prefer for the 1811-12 quakes to have been record-breakingly strong—because it makes the book I’m writing juicier—but as a person who lives in St. Louis in a brick house, I’m hugely relieved by the data of Seth Stein.

So why do so many other Missourians, most of whom are not, I suspect, writing novels, seem strangely disappointed by and even defensive about this potential downgrading of a natural disaster? Maybe, in our age of nonexistent weapons of mass destruction and sham celebrity weddings, it’s just hard not to be cynical. Or maybe it’s that Midwesterners know we’re not considered particularly interesting by the nation as a whole, and we’re loath to lose one of our few marks of distinction. (Already, Missouri jeopardized its status as a bellwether state with the 2008 presidential election.) Or could it be for the same reason that people watch horror movies—because suspense makes everything more exciting? As it happens, I hate horror movies, but then again, I find everyday life sufficiently terrifying.

Michael Wysession is a professor in the Department of Earth and Planetary Sciences at Washington University in St. Louis, as well as a former student of Seth Stein’s. When I met with Wysession not long ago, he said he, too, has noticed resistance to the idea of less momentous 1811-12 earthquakes or of a shutdown fault, even among some of his scientific colleagues. But when I pressed him on why people are reluctant to believe something that can only, if true, mean we’re safer, he indicated that this was a matter beyond the scope of seismology. “You’d have to ask a psychologist,” he said.


Earthquake causes fluvial tsunami in Mississippi - HISTORY

200 years ago this February 7, on the western frontier of European settlement in North America, the pioneering westward expanders and the natives whose land they were colonizing were thrown from their sleep in the deep wee hours of a winter night by the culminating temblor of a harrowing, months-long sequence of major earthquakes, aftershocks of which continue to this day.

Map of shaking intensity interpolated from historic accounts of the 2:15am mainshock of the New Madrid sequence. Map courtesy Susan Hough, USGS.

The so-called New Madrid earthquakes–named for a small Missouri settlement near the modern-day borders of Kentucky, Tennessee, Illinois, Indiana, and Arkansas that lay nearest the center of this cataclysmic seismic sequence–are the largest to have struck the eastern United States since well before they became the United States. In the recorded history of western settlement of North America, no quakes outside of the mountainous west match them in size and scope, and only a few come close.

Plenty of people have been and will be reporting on these earthquakes as we celebrate their bicentennial, including the organizers of the Great Central U.S. ShakeOut, which took place this morning to commemorate the massive culminating temblor of the sequence that started in December 1811. Even mapping software purveyor ESRI has put together a commemorative compilation of informative and beautiful interactive maps about the quakes (super cool compilation! If you click on one link in this post, let it be that one). It is worth reading some of these syntheses and reviews because the earthquake series itself makes a captivating narrative. It’s nearly impossible to imagine the terror with which these relentless temblors must have stricken the settlers, who were already braving the “wild” frontier of a foreign continent. Even the mid-continent’s native inhabitants had not experienced such a thing in scores of generations, and in the early 19th century no one would have had any reasonable framework in which to explain the occurrence of massive earthquakes.

Because the New Madrid quakes occurred so early in our country’s recorded and geographic history, piecing together the events with a modern understanding of earthquakes and plate tectonics has required a great deal of sleuthing, and some of the details gleaned about them remain controversial, most notably their magnitudes (were they more like M7 or more like M8?). The uncertainty regarding the exact size of these earthquakes compounds the issue of determining the seismic hazard posed by recurrence of major earthquakes in the New Madrid Seismic Zone. To understand how seismicity may continue in southeastern Missouri we can look for patterns in the prehistoric record of earthquakes, but ideally we would like some idea of what forces caused these earthquakes to happen here. This remains an open question, and one in particular for which the question of the quakes’ magnitudes may be a crucial bit of information. Researchers have tried to use modern seismicity to constrain the behavior of large earthquakes in the New Madrid Seismic Zone, and some have interpreted the ongoing small quakes there as the tail end of an unsurprising aftershock sequence, suggesting that they don’t represent heightened seismic risk, but that in fact New Madrid is as likely as any number of other places in the eastern U.S. to have more major temblors.

The ongoing scientific controversy over ambiguous interpretation of details of these quakes stems from the nature of the data. Researching “pre-instrumental” earthquakes is a pursuit that fuses seismology, history, and social science, in an effort to understand historic written accounts of the earthquakes in the context of their time and cultural setting. A somewhat recent article in Seismological Research Letters describes the endeavor of anecdotal seismology, and through some colorful examples illustrates how historical reports can be translated into seismological data, clarifying the sources of interpretive ambiguity. The marriage of historical and seismological research to inform our model of seismic events in the eastern U.S. could be and has been the subject of many volumes, so I can’t hope to cover it here.

Instead I’ll draw analogy to this incredible sequence of earthquakes through videos and pictures from recent events, hopefully grounding some of the legendary accounts in footage of real and recognizable phenomena.

To the extent that people have learned about the New Madrid earthquakes of 1811-1812, they have often heard of them referred to as the largest quakes to ever strike the U.S. Ask California [1857 & 1906] and Alaska [too many to name] and you’ll find this claim is far from true. Along with this hyperbolic appraisal comes the legendary confluence of phenomena eyewitnesses allegedly reported: the Mississippi running backwards, giant fountains of water issuing from the Earth, trees being thrown to the ground, and land sinking into the river. The unimaginable chaos of these phenomena all occurring in the midst of violent shaking defies belief, but contemporary earthquakes and modern video recording technology allow us to ground them in reality, and perhaps to understand them as more modest individual events that have been amplified in intensity by their conflation and coincidence in legend. We can see examples of all four in much more modest earthquakes:

1. The Mississippi running backwards

It’s difficult to imagine what possible physical phenomenon could have led to this observation/claim… unless you understand that the New Madrid quakes–just like all other large temblors–resulted from slip along several geologic faults. At the surface, fault slip breaks and displaces the ground, moving one side in a direction opposite the other. In the case of the causative Reelfoot Fault, the surface trace cut right across the Mississippi River channel, dropping an upstream portion of the river relative to the adjacent reach downstream. This warping has been thoroughly investigated and modeled, and thanks to the September 4, 2010 Darfield earthquake–a M7.1 event that ripped across rivers on New Zealand’s flat Canterbury Plain–we have a beautiful modern analog of the occurrence.

Aerial view of the Horata River spilling off of the fault scarp formed by the September 24, 2010 Darfield earthquake in New Zealand. Image courtesy Dr. Mark Quigley, University of Canterbury, Christchurch, NZ.

Where the 2010 NZ rupture fault sliced across the Horata River, it diverted the water into surrounding farmland, effectively changing the course of the flow. This is precisely analogous to the diversion of the Mississippi that led to both the damming and formation of Reelfoot Lake, and the temporary diversion of river flow back upstream.

2. Fountains of water issuing from the Earth

There are a few processes that may combine to produce this effect. In the past year we’ve seen plenty of examples of sand volcanoes, the eruptive results of shaking-induced soil liquefaction. When subjected to seismic waves (as in this New Zealand aftershock, or the Tohoku quake below), these sand blows can be squeezed into fountains of substantial height. The force of a larger and longer earthquake would undoubtedly increase the height these reach.

Extrusion of liquefied sediment by seismic waves isn’t the only coseismic phenomenon that may throw water high into the air: seiching–harmonic oscillation–of small bodies of water may throw water against their banks and up into the air. We’ve seen this dramatically demonstrated in swimming pools during a M7.2 earthquake, but natural ponds don’t necessarily have the splashing power of sharp corners and hard edges in concrete-walled pools. Nonetheless, with these two phenomena operating in tandem, the amount of water being thrown into the air by the quake would certainly be fodder for tales–legendary or not–of high fountains from the Earth.

3. Trees being thrown to the ground

Videos from several modest (M

6) earthquakes in the past few years have revealed just how much trees can be wrenched around during shaking. Under the accelerations of earthquakes, trees’ own weight can be a more powerful force than high winds. Here a stand of neighborhood trees sways in a mere 4.4 earthquake in Christchurch:

In a M6 we see through the windows the same effect:

Finally, video the USGS captured at practically the epicenter of the M6.0 2004 Parkfield earthquake shows fairly violent lashing of late summer oaks in the California Coast Ranges.

A tree along the San Andreas Fault in Wrightwood, CA, had its top snapped off in an 1812 earthquake, from which it grew two new crowns. The tree no longer exists, but others like it can be found along the 1906 rupture near Point Arena in NorCal. Image from "Mixed Matters"

Though the effects shown above do not amount to trees being thrown to the ground, the earthquakes that produced them were much smaller than the ones that struck Missouri. We have clear evidence along the San Andreas Fault of trees whose tops were snapped off during the 1906 earthquake. This is a common effect in the epicentral region of large quakes.

4. Land sinking into the river

This phenomenon is akin to but distinct from the Mississippi being diverted and running backwards. In fact the underlying process is more closely related to the processes that give rise to sand blows. Shaking liquefies water-saturated soils and they lose their shear strength, rendering them unable to support gravitational loads. Thus the land slumps, under its own weight or the weight of trees, houses, or riverboat moorings, downhill towards unencumbered free edges like river banks. This “lateral spreading” is commonly observed along river banks shaken by earthquakes, and results in lowering and inundation of the ground surface. Examples abound from earthquakes as geographically and tectonically various as the 1964 Good Friday event in Alaska, the 1906 San Francisco earthquake, the 2010 Haiti earthquake, and the 2010 El Mayor-Cucapah earthquake. In all of these events vast swaths of land shook loose and slumped ocean- or river-ward, and effectively “sank”.

The video examples compiled above may not match the apparent drama of those recounted from 1811-12 Missouri, but I find it easy to imagine the cumulative results of decades and decades of re-telling on the details of these accounts. In any case, large earthquakes produce remarkable effects, and although many people around the world witness or experience earthquakes, still relatively few witness the truly violent shaking that occurs near an earthquake’s source. Written and oral accounts give us the most thorough picture, even if we have to take them with a grain of salt. Video may gradually be replacing verbal accounts in objectivity (no relying second-hand information!), but it has yet to become as widely distributed and available as individual eye-witnesses.

Next time you strike up a conversation about these earthquakes, consider yourself informed about many of the features that defined them, but by all means gather more information on your own. My two favorite informative links are the following:

List of site sources >>>


Watch the video: Οι χειρότερες φυσικές καταστροφές Η ΑΠΙΣΤΕΥΤΗ ΔΥΝΑΜΗ ΤΗΣ ΦΥΣΗΣ (December 2021).