The Sphere of Gravitational Influence Explained

 The sphere of influence (SOI) is poorly named and should include the word dominant because the influence of other objects is not excluded. It is the outer edge of orbital stability, making a stable orbit difficult to achieve at that location. The SOI is tied to a less massive object that orbits a more massive object. So the sphere of influence for the moon is that space where the gravitational pull of the moon is stronger than the Earth's. The SOI for the Earth is a space where Earth's gravity is stronger than the Suns which extends out about 1 million miles from the Earth.  So in effect, the SOI for the moon is a hole in the SOI for the Earth. The SOI for the Moon extends out about 40 thousand miles from the Moon's surface. Inside this sphere, the gravitational pull of the Sun and Earth is still there, just weaker than that of the Moon. Escape velocity is the velocity required to get to the SOI when launching from the surface.

THE BARNACLE THAT ESCAPED FROM STARKVILLE MISSISSIPPI

My historic single cretaceous barnacle from the Starkville area is Arcoscalpellum withersi Collins which was collected in 1970 with Dr. E.E. Russell’s fledgling undergraduate Historical Geology class. That class also included Michael Bograd and David Dockery that went on to much greater service for the Bureau of Geology with the State of Mississippi and later with the Department of Environmental Quality. Dr. Russell gave us these instructions” What we are looking for looks like a little dugout canoe. You’re not going to find them by just walking around you have to get low to the ground maybe on your knees.” He was right. Not only are these small but the same color as the chalky outcrop. I found several but he let me keep this specimen. I didn’t know why until years later I decided to identify it. I then realized I got to keep it because the pointed tip was broken off on one end. At the same time

I discovered that this fossil was a new species when I found it. It was not named for 3 more years until Collins and Mississippi’s Fredric Mellen published their classic 1973 paper: CIRRIPEDES FROM THE UPPER CRETACEOUS  OF ALABAMA AND MISSISSIPPI, EASTERN GULF REGION, U.S.A. This paper includes the following acknowledgment: 

The writers are greatly obligated to many people for assistance in the collecting, preservation, and study of the cirripedes covered in the present work: to Professors Troy J. Laswell, Ernest E. Russell, and Donald M. Keady of the Department of Geology and Geography at Mississippi State University for assistance in collecting and encouragement of student participation, and for affording a repository for barnacle collections and literature in the Dunn-Seiler Geology Museum.

I could have lived next door to the gully where we went to fossil hunt in 1970 and never noticed these odd-looking little fossils less than 1 inch long. But we learned on that day that all fossils have a story to tell (big or small), some more than others. When this barnacle lived about 70 million years ago there were giant sea turtles and even bigger mosasaurs that swam past this little bottom-dwelling guy every day and also never noticed him. But because he somehow got broken maybe by a wandering cow, he wound up with an amazing history and his own blog page.

DRAINAGE FOR YAZOO CLAY

This blog is about residential structures built with slab foundations in central Mississippi but it could also be used for residences with crawl spaces in this area. In this area lies one of the most active expansive clays in the world. It is called Yazoo clay. When this clay surface is above a depth of 10-11 feet of the surface, you should have adequate fall away from the house (positive drainage) on all sides. We often refer to this elevated surface around a residence as a berm. Typically you would need a fall of 8 or 9 inches in a 6 to 10-foot perimeter from the house with a Yazoo clay depth of 8 feet. In addition, the surface water that runs off of this berm must also be properly drained away without ponding. This is so important that it should be part of a local building code. This well-known construction fact is still violated by some home builders. Often the violation occurs on terraced lots where the lot is too small for the house. When this happens it is impossible to construct proper drainage away from the house without expensive retaining walls. These houses are often abandoned by their owners 10 to 15 years down the road when the owners are confronted with the cost of releveling plus a retaining wall and drainage that should have been part of the original construction. 

With less active clays like we find near Dallas and Austin Texas, these same rules would apply except that these less active clays must be closer to the surface than the Yazoo to create this need for good surface drainage. Surface drainage problems often go unnoticed in planting areas next to the residence that are covered with mulch. Typically depressions from erosion occur around the edge of residences that do not have gutters. Sometimes the depressions are inadvertently created when the planting is installed. To discover these areas the mulch must be removed and replaced.

There are 3 ways to improve drainage other than constructing retaining walls. There are two ways to improve surface drainage plus subsurface drainage. Retaining walls can be added to surface drainage to lower the grade and improve slope away from the residence. Surface drainage should be improved when water stands in puddles and maybe when the ground is mushy after rains in the same areas. Surface drainage might be improved by constructing drainage swales through a poorly graded yard. Otherwise, catch basins are installed with drain pipes. There is a significant improvement in quality when smooth pipe and concrete boxes are used. Higher quality systems are required when the ground is flat or there is potential for leaf or pine straw to clog the pipe.

Generally, subsurface drainage in central Mississippi should be designed by a qualified engineer. Subsurface drainage is only installed to remove groundwater. In central Mississippi, this is almost always a perched water table that is created above an impermeable layer like Yazoo clay that should be at least 6 feet deep. If your drain is not as deep as the impermeable layer the groundwater can just pass underneath the drain. Poor subsurface drainage is hard to detect without soil borings. Be very cautious if someone recommends subsurface drainage without the aid of soil borings. If water is not initially detected in the boring then they should be left open for at least 24 hours. You might detect groundwater with hand-dug holes if it has not rained in a week or so. But typically hand-dug holes will not be deep enough. Note that water standing in a hand-dug hole a day or two after a hard rain might just be surface water that has saturated the upper layer of soil and may not be a condition that justifies a subsurface drain. Also if you suspect a leaking water line, you can test the water in a boring for chlorine and sewer bacteria.

I typically recommend drainage repairs when foundation movements are moderate or severe. I also correlate drainage issues with the floor elevations. This kind of evaluation is described in explained in a blog with the title:   Investigating Slab Foundation Failures in Central Mississippi.

How to Find your Family Tree with Ancestry DNA

This blog is about the Ancestry process using DNA that you can use to expand your family tree when you have hit a brick wall or a dead end from genealogical records. It was updated on 8-12-19 on 9-29-2019  and again on 12-4-2019. If you follow this process you could discover an error in your tree or expand it past all known records and then maybe you can become the Einstein of your family genealogy. Now I am assuming you were not adopted, so you know your parents and grandparents. If you were adopted the process is different. In this case, you start with your match list under the DNA tab at the top of the main Ancestry page. This is a list of your closest cousins. This list also shows the size of their family tree. So if you were adopted you begin by looking at the trees of your closest relatives. I will discuss this process in more detail at the end of this blog otherwise, please read on.

After working on my family tree since 2016, I still had two 2nd great-parents without any known parents. Breaking out of this deadlock to me was a huge and exciting advance in the genealogy of my family. In my case, there was a popular family picked by my other Ancestry cousins as the next or the 3rd generation. But no DNA evidence or records surfaced that supported this theoretical expansion of our family. I did not realize that Ancestry was telling us in a very indirect way that our theoretical next generation as we thought was almost certainly wrong. If you have expanded your family tree in error then Ancestry DNA has a way of telling you of your error. You simply have no DNA matches with the part of your tree that is in error.

In the last few months Ancestry has made some improvements that helped, but breaking through came only with a better understanding of how Ancestry was processing my family tree. What I realized was that if I could correctly guess either one of my 3rd great grandparents then there is a very good chance that Ancestry DNA would in-time verify my guess by showing new DNA matches with other cousins related to my new theoretical great grandparents. But the trick is, that if you guess wrong you must abandon that guess if you get no DNA matches with your new theoretical great grandparents. When you guess wrong it is like removing the DNA engine from your car; in-effect Ancestry can no longer help you. This is because Ancestry is trusting your research and attempting to verify it with DNA matches. How long does this process take? I don't really know, but for me, it took about a month for DNA matches to appear once I made a correct guess. An important point is that if you get just a handful or less of DNA matches eventually more will probably appear. This may happen because of improvements in processing or by the addition of new DNA Ancestry members. This is an area where you can help Ancestry by verifying the DNA matches that are flagged "evaluate," These are DNA matches that might be wrong. There is no single tree that makes the connection or used trees have conflicts or possible errors. So here your job is to work your way down as far as you can to your cousin in your tree. This process could help Ancestry find additional DNA matches. Once you do this the "evaluate" flag will eventually go away.

Ok, let's back up a bit. First, before you go this route you need to be sure you have exhausted all your genealogical resources. This means that you have looked in detail at the last known family. This includes all the children as well as the parents. You have no duplicate people and you have a family history up to your dead-end that makes sense.

A lot of times you find one or more children who were born out of the area that the parents were known to have lived. These should be deleted. Be sure all the children were born within the childbearing age of the parents. Once you have done all these it's time to move to the process below.

Ancestry requires 3 things to do what I am talking about. You must make a family tree up to your dead-ends, then you must correctly guess your next generation of grandparents then you must also take an Ancestry DNA test and allow time for Ancestry to process your data. This process should work in most cases out to about 5 or 6 generations or maybe a bit farther. Now we must understand that there may be smaller families of our ancestors who have descendants that have not taken DNA tests. So in these cases, this process might fail. But in order for this to happen, you may need to have 2 or more back-to-back generations with only 1 or 2 children that also had children. Now one last point: how do you guess the names of your missing ancestors?

I start by using the last name only of the last known father. Then I assume he was 20 years old when he had your grandparent. Then I begin searching, changing and adding possible information. As I progress I add to the age in 4 or 5-year increments. Next, I start guessing the state where your ancestor died. Next, I start guessing the state where my ancestor was born. As I progress I make a list of possible ancestors. Start with the state where your known ancestor lived and then progress to adjacent states. When you pick a possible parent, be sure that his age is realistic.

Finally, I  think you know for sure you have discovered your true lost ancestor when you get multiple DNA matches with your new ancestor. The best way to see these is through Ancestry's new ThruLines tool. You have to enable this from the Extras tab in Ancestry (select Ancestry Lab). This tool works out to your 5th great-grandparents. I access ThruLines from the horizontal family tree. Basically, this is a list of DNA descendants of your ancestors. This tool will patch together several people's family trees to show you how you might be related. To be sure this is a DNA match you need to add this person to your tree by working down from the common ancestor. Now if you only have 1 or 2 matches with a theoretical new ancestor you still might be wrong, because it may be that you are really related to these DNA cousins through some other unknown route. Also, note that you may have dead ends in your tree and not realize it. If you built any part of your tree by borrowing other member's trees, you need to use ThruLines to verify your whole tree out to the 5th generation.

Before I conclude there are some good rules to follow when you use Ancestry. You can borrow or import families from other people's trees. But when you do this be selective. I pick the 2 best looking family trees. These are trees with a lot of records but also trees without obvious mistakes like double people. If you import double people by mistake (and you will - do this) you simply merge the 2 people together. Once you import a family, try to verify it with a census, birth, and death records available in Ancestry. Finally, it's easy to forget that you have made a guess about your tree at some point. To help you Ancestry has added TAGs that you attach to a person that indicates to you that this person is a hypothesis. Also, add a comment to the person to tell other cousins what you are doing.

IF YOU WERE ADOPTED

If you were adopted your family history is inverted. From your DNA match list, you know the name of some distant or maybe a close ancestor. So instead of having a family tree, you have some ancestor that you are related to. So you must work from this person down to you discovering all the children of these known ancestors. You are a descendant of this person and if a thorough list of descendants is made you and your parents will appear in this list. You need to carefully watch the TV show "Long Lost Family." This show is sponsored by Ancestry.com. The hosts of this show were adopted themselves and they do the detective work using DNA to help people reunite with their DNA parents. In this show, they emphasize that you need to work with all the information that you know about your parents and your adoption process. On occasion, the breakthrough comes from a long list of possible family aunts or uncles that are contacted one-by-one on the phone. But if you are lucky, one of your parents or grandparents have taken an Ancestry DNA test. So, in this case, your closest DNA match could be one of your parents. I highly recommend that you in your Ancestry profile explain that you were adopted and tell the community your closest known DNA cousins. If you would like to have assistance please contact me.


Note if you see an error in this Blog please do not hesitate to contact me.

The Natchez Revolt in the Mississippi Territory in 1781-The Last Year of the Revolutionary War

INTRODUCTION: The Mississippi Territory was under Spanish control at the time and not part of the 13 colonies. However, the Spanish joined in on the side of the colonist in 1779. Interestingly two years later a pro-American faction joined with British loyalist against the Spanish government in the Natchez District of the Mississippi Territory. The territory was controlled by Fort Rosalie that was first built by the French in 1716. Mississippi would not become a state for over 100 years, it was only 17 years away from becoming a US territory. This fort was first destroyed in a conflict with the Natchez Indians and it was rebuilt in the early 1730s and again about 1778 when it was occupied by the British. The following is a look at the Natchez Revolt of 1781 as it took place right before the final battle of the American Revolutionary War at Yorktown. For me, this revolt also created a genealogical record of my 4th great grandfather showing that he and maybe his future wife had a front-row seat of this event. At the time there were only a few hundred settlers in the Natchez District of the Mississippi Territory. The primary reference for this post is “The Natchez District and the American Revolution” by Robert V. Haynes.  This blog is my 2nd most popular was updated on 8-27-2019 and again on 11-22-2019.

THE HISTORY: On May 8, 1779, the American War of Independence (1775-1783) was given a boost when a formal declaration of war against Britain was made by King Charles III of Spain. Another declaration was made on July 8. This “authorized Spanish colonial leaders to engage in aggressive action against the British forces. Directly following this decree, Governor of Spanish Louisiana, Bernardo de Gálvez, began planning offensive actions against the British.” On September 12 they began a siege against the new British fort at Baton Rouge. The battle ended with a Spanish victory on September 21, 1779.  The conditions of British Lieutenant Colonel Alexander Dickson’s surrender included surrounding the infantry soldiers at the Fort Panmure, at Natchez, Mississippi. Fort Panmure was originally named Fort Rosalie by the French, but it was renamed when the British took control in 1763.

The Spanish occupation of Fort Panmure and the Natchez District of the Mississippi Territory was briefly interrupted by the British inspired Revolt of 1781. General Campbell at the British fort at Pensacola played a significant role in this revolt but locally there were two instigators named Philip Alston and John Turner. With a joint effort, they convinced John Blommart, a reluctant loyalist, to join in and lead the revolt. The insurgents were advised that British troops and supplies would be sent to support them and that they should recapture Fort Panmure.

With this promise of support, the British loyalist attacked Fort Panmure on April 22, 1781, with 200 men and only one cannon in their arsenal. This attack failed. However, they managed to trick the Spanish to abandon the Fort. They did this by intersecting message from a “Spanish sympathizer.” They replaced him with an imposter complete with forged papers and replaced the message so that it now read that the fort would be destroyed by an explosion of gunpowder unless the Spanish withdrew.” The rebels took control of the fort and the Natchez District on May 4, 1781. However, there was immediate descent among the victors. There was a pro-American faction that wanted to handle things differently from Captain Blommart. At stake was what to do with the Spanish prisoners and the supplies and ammunition from the fort. However, the victors soon realized that there would be no British support because Pensacola fell to the Spanish a week later on May 10. The pro-American faction wanted to divide the spoils equally and flee to the countryside and hold out until reinforcements arrived from the United States. Blommart disagreed and appointed a commissary to dispense the supplies only as needed.

Natchez was re-occupied by a combined force of French, Indian, and Spanish troops on June 22, 1781, only 2 months after the revolt started. “This Spanish force was under the command of Captain Esteban Roberto de la Morandiere and consisted of sixty-six militiamen, forty-three native warriors, and forty French-Canadians.” This force landed at Natchez unopposed and began to reoccupy Fort Panmure, the town of Natchez, and the Natchez District. The next day a detachment of 20 militia and some 80 inhabitants began rounding up all the known rebels still in the district. However, most of the rebels had fled the area and were planning to take refuge with the Indians. The largest colony of these refugees wound up around Chickasaw Bluffs (now Memphis). A month later Colonel Don Carlos de Grande Prè became the commandant of Fort Panmure. He took measures to punish the insurgents and imprisoned seven and charged them with promoting a general rebellion against the government.

The Natchez Court Records adds a tidbit of information about this rebellion not mentioned in other historical accounts I found. This record states that “the revolt took place at Natchez and the widow Truly having built a fort or block-house on her land or the land of Benet Truly and the rebels who took refuge there, fearing they should want water if attacked by the power against them, dug a well.” We would not know this fact, except that, prior to this rebellion Benet Truly had engaged a Thomas Rule to dig a well on this same property. So a year later on April 11, 1782, the court demanded that ”Thomas Rule shall dig the well which he contracted for on the plantation of Benet Truly. The said Rule having been paid for it and the well shall be dug in the season customary in this district. Sig: Grand-Pre.”

Before I continue I have to add that this Thomas Rule is my 4th great grandfather. I knew almost nothing about him until I found court and land records from the Natchez District. I will return to his story but let’s get back to the rebellion. With a bit of speculation, we can mesh the story of the well at the plantation of Benet Truly with the bigger story outlined above. This is what probably happened: When the insurgents at Fort Panmure got word that they were not going to be helped by the British they realized that they had no chance against the approaching Spanish force. Some disbanded and others remained at Fort Panmure. Only a small contingent of the insurgents remained in the Natchez District and they decided to hold up at the Benet Truly plantation where they dug a well. This group fits within the non-local pro-American faction without ties to the Natchez District. In the American colonies, a bigger engagement with the British was about to happen that would result in the end of the Revolutionary War.
 
On September 28th of the same year - George Washington commanding a force of 17,000 French and Continental troops, began the siege known as the Battle of Yorktown. This battle against General Lord Cornwallis was the most important battle of the Revolutionary War because “after three weeks of bombardment... Cornwallis surrendered on October 15, 1781, effectively ending the War for Independence. Prior to this battle, George Washington cut off the escape of Cornwallis by land and sea with brilliant coordinated effort using the French fleet from the West Indies lead by Comte de Grasse.

We see from the shortlived Natchez Revolt that the Natchez District was politically a world apart from colonial America at the end of the Revolutionary War. It appears that the time that a significant portion of the population must have been British Loyalist that opposed the Spanish government. This is an interesting change from a settlement that was first started by the French. This concludes my historical account of the Natchez Revolt of 1781 and the close of the Revolutionary War.

THE MYSTERY OF THOMAS RULE SR AND HIS WIFE ELIZABETH: I am hoping this historical background will help to solve the mystery of my 4th great grandfather Thomas Rule. Who was he? Who did he marry and where did he come from? This is what I know. Thomas was in the Santa Catalina area of the Spanish Natchez District Census of 1792 and from the court records mentioned above he had to have been in the Natchez District as early as 1781. He was eventually married to someone named Elizabeth and they bought property in the District. He died sometime early in 1804 in the Natchez District. They apparently had two sons, Thomas Rule (1786-1850) and Nathan Rule (1792-1869), but there is no record found so far that connects this family together. The younger Thomas married Anna Christeana Jacoby (James) (1786-1853). They are both buried in the Rule Cemetery in Ebenezer Mississippi and they are my 3rd great grandparents. From a memoir written by Christeana’s younger brother (Peter), we know that she and her family arrived at Natchez on June 1, 1800, with her parents, 2 sisters, and Peter. Her parents were Bartholomew Jacoby (1747-1833) and Maria Catherine Mayer (1749-1820). They had traveled from Pine Grove in Berks Pennsylvania. The wife of Thomas Rule through DNA only seems to have been Elizabeth Holloway (1765-1812?) who came to the Natchez District with her parents and her brother Robert. Her youngest brother, James, was born in the Natchez District in 1779. Her father, John, was killed by Indians in Natchez 24 Oct 1781 when James was only 2 years old. To date the only connection I have found between Elizabeth Holloway and Thomas Rule other than DNA comes from the following court record:

P. 69  (about Feb 1783) Elizabeth Holloway vs Thos. Rule. She represents that Thomas Rule owes her $4 and 4 rials for carpenter's tools lent to him, namely one hand-saw and one chisel; asks for payment.

Thomas’s first son would be born about 3 years after this record, so this Elizabeth is hard to understand as the future wife of Thomas senior because she was married to a Cady Raby in 1781. There was another Thomas Rule (1761-1846) from Pennsylvania that lived about the same time as the younger Thomas in this story. This other Thomas died in Mercer County Kentucky and never lived in Mississippi. Just the same, he has been confused with both Thomas Rules (from Mississippi) in this post. He was having children in Kentucky up to 1811 and was buried in Kentucky so he does not fit in with records of these two Mississippi Thomas Rules.

Massive Martian Landslide found in Shalbatana Vallis using Google Earth "Mars"

Shalbatana Vallis Landslide (looking south). Image from Google Earth "Mars" 

This blog was updated on 8-22-2019 and again on 9-12-2022. The Shalbatana Vallis canyon is nearly 800 feet deeper than the Grand Canyon. In this canyon, there are several mudflows but the largest is a huge section involving seven and a half miles (11.5 km) of the eastern flank of this canyon that failed in a massive landslide that involves a total of 66 square miles (171 square km). What is most impressive is that the toe of the landslide liquefied and flowed several miles across the canyon floor and then 1/4 of the way up the west canyon wall. The Shalbatana Vallis is very roughly a 300 mile (480 km) long canyon that opens up into a wider valley on the south end before reaching the Orson Welles crater. It has a delta on its northern end (Chryse Colles) and that delta connects to the larger Chryse Planitia (Golden Plain). A different mudflow at the south end of Shalbatana Vallis was recently identified by Berman D. C. et al (2017).

The upper part of this landslide is similar to slump failures on Earth that form in cohesive soils with a high clay content that progressively fails over an extended timeframe. At the top of the slide there are a few tension surface cracks (see GE image below). In an active slide, these cracks will widen and form a new scarp with a new rotating slump block. The blocks are separated by minor scarps. This slide has 3 or 4 larger slump blocks with smaller ones between. Using Google Earth, a profile section was cut through the slide to determine elevations. The section location can be seen in the GE photo above (Fig. 1).  In the landslides I have studied in Mississippi the toe is a small percentage of the whole feature. But here the base or toe of the slide is longer than the slump. Clearly, the toe is acting more like a mud or debris flow in this slide. The toe of the landslide ran about 4 miles ( km) across the floor of the canyon and then 1200 feet (665 m) vertically up the west canyon wall. This flow indicates that this whole slide happened during a single (non-progressive) event.

Google Earth image of the Shalbatana Vallis Landslide from above
 (top of photo is south)

Using Google Earth coordinates, the south end of the scarp is located at lat 4.300975̊, lon -43.988396̊  and the north end at lat 4.497535̊, lon -43.991300̊. This landslide is not something that happened recently because several small meteor craters can be seen on the landslide surface. There are other smaller landslides in the Shalbatana Vallas and many hints of older landslides that appear to have lost most of their identity from erosion. But it is clear that no water has flowed down this canyon since this landslide occurred. There are numerous small craters in the floor of the canyon and a few larger craters that intersect the top edge of the canyon. These craters help date these features. When this slide occurred there was a significant influx of water to fuel the slide. It could be that a meteor impact created enough ground quake to cause the soil to liquefy thus causing the slide. But it is most likely that there was a rapid influx of water from water trapped in a cryosphere. There are large areas of the surface of Mars where the surface appears to have subsided and created canyons different from outflow channels providing evidence of this cryosphere. 

On Earth similar landslides happen after there is a large influx of groundwater from heavy rain. The influx of groundwater raises the pore pressures in the soil and reduces its shear strength. The factor of safety against sliding drops to unity and the side precipitates. A soil that has shear strength and then suddenly turns into a mudflow, indicates a soil that may have obtained its strength due to some cementitious agent. The key point is that the soil in the toe had to be saturated when this event occurred to produce this mudflow across the valley floor and up the other side of the valley. We know this from similar events on Earth. 

The location of this landslide was submitted as an observation candidate in Oct 2008 and the Mars Reconnaissance Orbiter HiRISE camera photographed a strip of the slump area of this slide (See http://hirise.lpl.arizona.edu/PSP_010461_1845). However, the mudflow at the base of the side was not included. The nearby smaller landslide mentioned above was identified as a landslide and was nicely imaged by HiRISE 04 November 2007. See “Landslide in Shalbatana Vallas” http://hirise.lpl.arizona.edu/PSP_005965_1855 and again on 10 Jan 2009 (see http://hirise.lpl.arizona.edu/ESP_011529_1855).


References:
Berman, D. C., Weitz, C. M, Rodriguez, J. A. P., Crown, D. A, “Geologic Map of the Source Region of Shalbatana Vallis, Mars.” 3rd Planetary Data Workshop 2017.

Google earth images: NASA/USGS
ESA/DLR/Fu Berlin (G.Neukum)

Christmas Parade 1948 or 49 Jackson Ms

A Christmas Parade in downtown Jackson Mississippi in either 1948 or 1949. The location is the corner of North State Street and Capitol Street. Buildings in the footage include Hemphill Drugs, Gandys Steaks, The War Memorial Building and the Old State Capitol Building. Footage was shot by my father, Clyde Maxwell. Many years later my mother and father re-shot the footage on an 8 mm camcorder and added the narration. The background noise is daddy's 16 mm film projector.

Investigating Slab Foundation Failures in Central Mississippi

This post was updated on Oct 28, 2017,  Dec. 21, 2018, and again on June 3, 2020. In this post, I provide a simple method for determining the seriousness of a foundation problem. At the lower end of this scale, you might consider only repairing the cracks. At the higher end of the scale, you would want to relevel and repair drainage problems. However, there is also an issue as to the kind of movement that has occurred. Most foundation failures we have investigated have a mixture of distortion and tilting. If it's mostly tilting then there is little or no damage to the slab. But if it is mainly distortion then the movements have damaged the slab through bending. These aspects are rarely considered by foundation investigators but they should be. The only way to make this determination is to draw elevation contours of the floor using a comprehensive elevation survey as I describe below.

A minimum foundation check should involve a complete floor elevation survey that should at least accurately describe the locations of the highest and lowest floor elevations. The survey plot should have enough detail so that anybody can locate those two points. The evaluation should include a calculation of apparent maximum differential movement which is the difference between the highest elevation and the lowest elevation corrected for any differences in floor thickness between those two points. A much more meaningful survey is one that has either the low point or the high point equal to zero. All of our surveys are done this way. The best way to accomplish this is to spend a few minutes scanning the floor elevations with a Zip level to find the low point. Once this has been found, zero the Zip level to the lowest point. When this is done it becomes much easier to draw floor elevation contours. But note that floor elevation contours only have meaning if you plot the elevations on a scaled floor plan. I should note that these things are not typically done by foundation contractors. Most elevation surveys made by contractors do not have a datum at the low point or the high point and are not drawn to scale. Some elevations are negative and some are positive. This kind of survey appears to be cryptic to a novice and just hard to evaluate even by experienced engineers. If this kind of survey is your only guide, there is a good chance that you will miss subtle drainage problems that are connected with the movement. So when I get this kind of survey the first thing I do is to shift the elevations so they are all positive. You can do this yourself. If the lowest elevation is -2 inches, just add 2 inches to every survey point. It's the same data but now it's easier to interpret and to contour.

The literature on slab foundations constructed on expansive soils recognizes two failure modes: one is edge-lift and the other is center-lift. All the failures we have seen in central Mississippi where expansive soils are present, fit into these two categories. It is important to recognize that edge-lift failures are often related to poor drainage near the higher floor elevations. Center-lift failures may be related to a perched water table or poor drainage several places around the house. Before investing thousands of dollars in a foundation repair, homeowners should have a better quality floor elevation survey made that more clearly shows the movement, identifies the failure mode, and shows how that movement changes across the foundation.

The average annual movement can be computed when the age of the structure is known. Experience has shown that the average annual movement rate tends to continue unless repairs are made that specifically address the cause of the movement. A cookie-cutter foundation repair that just involves releveling will not reduce the movement rate if the movement is heaving (upward) from expansive soils. Many of the foundation releveling procedures will help to retard settlements.  But many foundations in Mississippi have a mixture of settlement and heave. Some in central Mississippi are all heave (uplift). My view is that when the movement rate is over 1/4 inch per year you have a potentially serious foundation problem that probably includes significant heave. The worst-case scenario is when the movement rate is 3/4 inch per year or maybe a bit higher. The 1/4 inch per year limit is strictly an arbitrary number. I assume that no one wants to have foundation repairs done any more often than once every 12 to 15 years. So over this time frame, you can accumulate 3 to nearly 4 inches of differential movement with the 1/4 inch per year arbitrary limit. Total movements in this range is a limit that is often used in the real estate industry.

Experience has also shown that if a structure has an average movement rate of about 1/4 inch per year that damage will begin to show when it is about 3 to 5 years old and that damage may first look like minor cosmetic issues. By the 5th or 6th year, the damage begins to look more like it is related to foundation movements. So if you buy a house that is less than six years old it could have a fairly significant foundation issue that might only show up through a floor elevation survey. So for a rule of thumb in central Mississippi, I recommend that if you are buying a house that is newer than say 6 or 7 years and does not show any evidence of foundation damage, the floor elevations should be checked and the average annual movement rate computed. A residence that may not need a foundation check would be at least 8 years old and show no damage that might be attributed to foundation movement.

I recommend a detailed foundation evaluation for any residence with a 1/4 inch or more annual movement rate. The detailed check should include the minimum check requirements and floor elevations and contours plotted on a scaled floor plan with a zero elevation datum. If the owner does not provide a scaled floor plan then the house has to be measured and a floor plan produced with those measurements. With a detailed check, I usually show the lowest elevation equal to zero. Elevations are adjusted for different floor thicknesses. I show on the plan the base elevation survey measurement and the adjusted elevations, I then draw floor elevation contours at ½  to 1-inch intervals. Using this plot as a guide I then look for contributing drainage issues. This may mean a second trip to the property. In addition to recommending the kind of foundation repair, I may recommend checking the plumbing lines for leaks or soil borings. Generally, I like to see these things done before I make recommendations for repair, but a soil boring can be made later as a check against your conclusions made with just the survey. If I suspect heaving from expansive soils, then I may request a 10-foot deep boring nearest the highest elevation to see the depth of the clay (CH soil) and possible contributions of a water table.

The benefit of the detailed foundation study is that it maps out the details of the movement. It shows the areas of distortion (bending in the slab) and what parts of the house have more slope than others and sometimes directs you to a serious problem like a broken plumbing line or an area with poor drainage. If an area of poor drainage is resulting in heave, the slope of the slab may continue to increase as you get closer to the source of the water. When you see this a classic edge lift condition has been identified that is well documented in the literature. It is also important to look at how nearby larger trees are related to the movements.

Following this procedure, it is possible that a newer house with minimum damage could be flagged because the movement rate is excessive. This does not mean that it has a foundation problem, but that it is at higher risk for future foundation problems. With a detailed study of the structure, maybe a related drainage problem can be found and corrected. Also, there are exceptions - not every structure with a high movement rate will continue to move at that rate and there is another issue in that not all structures with differential movement will result in wall cracks. It is rare but a structure can move so that it has an even slope across the whole structure (pure tilt). In this case, the only damage is floor slope. Whereas there are no cracks, it does make the structure less usable if the slope becomes excessive.

A Link to:What Happened Before the Big Bang

In January 2016 I proposed that the big bang was the result of an expansion of a black hole that had achieved a maximum density. I named this process "Parent Black Hole Cosmology". In my conclusions, I state that: Scientists believe that a previous universe may have contracted to a point and then bounced to create a big bang and our universe. But I think that bounce cosmology is just a special case of all possible bang events that could occur when we consider quantum gravity in a multiverse environment. I think that if we want to consider all possible bang events in a multiverse where quantum gravity functions, we must also consider bang events from black holes that are equivalent to a contracting universe. So when we move bounce cosmology into a multiverse, another path to a bang becomes possible because the bounce occurs at some maximum density and that same density could eventually occur in a black hole if it obtains enough mass.

If you find this thought process interesting I invite you to read my complete blog at this address: http://www.the-cosmic-corner.com/2016/01/what-happened-before-big-bang.html

3/24/2020 Note This Post was inadvertently deleted. So I am updating it and I will repost.

Biblical Accounts of Volcanic Eruptions with Tsunamis-Part II

“a huge mountain, all ablaze, was thrown into the sea” Revelations 8:8

In part I of this blog I reviewed the geologic and geographical setting of the Mediterranean and looked at a detailed account of a volcano in 2 Samuel 22. In the second part, I look at some passages that just hint at a volcano with a tsunami.  The Conclusions were updated on 8/25/2018 and again on 10/25/2018.

2.-- Nahum 1:3-8 This account provides much less detail but it still includes language that sounds like a tsunami. Pinker (2004) provides a theological perspective of this passage.

3 The LORD is slow to get angry. He is very powerful. The LORD will not let guilty people go without punishing them. When he marches out, he stirs up winds and storms. Clouds are the dust kicked up by his feet. 4 He controls the seas. He dries them up. He makes all of the rivers run dry. Bashan and Mount Carmel dry up. The flowers in Lebanon fade. 5 He causes the mountains to shake. The hills melt away. The earth trembles because he is there. So do the world and all those who live in it. 6 Who can stand firm when his anger burns? Who can live when he is angry? His anger blazes out like fire. He smashes the rocks to pieces. 7 The LORD is good. When people are in trouble, they can go to him for safety. He takes good care of those who trust in him. 8 But he will destroy Nineveh with a powerful flood. He will chase his enemies into the darkness of punishment.

ANALYSIS  In this passage references to a tsunami are: (4) “He controls the seas. He dries them up” and in verse 8 Nahum prophecies “ a powerful flood.”  Nahum’s possible reference to pyroclastic flow is interesting, in verse 3 he says “Clouds are the dust kicked up by his feet .” This is similar to David’s account in 2 Samuel 22: 10, but in this case, Nahum might be talking about a dust storm, because in verse 4 he seems to talk about a drought in the region from Carmel to Lebanon. But he may be connecting this drought as a possible environmental consequence the Thera eruption. Figure 2 is a map of the eastern Mediterranean Sea showing the location of Nahum’s drought, Thera, and other relevant locations. Other than the cross-reference with the possible pyroclastic flow, this account seems to be independent of David’s account of Thera. The possible mixing of the description of the volcano with other natural disasters is also done by Amos (see below).

OTHER POSSIBLE BIBLICAL PASSAGES
Again we are looking for any reference to something that sounds like a volcano and a tsunami in a Biblical passage. Amos uses a writing style where two chapters are joined into a single thought by repeating this phrase almost verbatim in both chapters:  “The whole land rises like the Nile River. Then it settles back down again like that river in Egypt.” If we use that bridge between chapters, we get a story of a possible volcano and a tsunami mixed with something that sounds like an earthquake and maybe an eclipse.

1.--Amos 8:8-9
8 “The land will tremble because of what will happen. Everyone who lives in it will mourn. So the whole land will rise like the Nile River. It will be stirred up. Then it will settle back down again like that river in Egypt.”
9 The Lord and King announces, “At that time I will make the sun go down at noon.
   The earth will become dark in the middle of the day.

     Amos 9:5-6
5 The Lord rules overall. The Lord touches the earth, and it melts. Everyone who lives in it mourns. The whole land rises like the Nile River. Then it settles back down again like that river in Egypt.
6 The Lord builds his palace high in the heavens. He lays its foundation on the earth. He sends for the waters in the clouds. Then he pours them out on the surface of the land. His name is the Lord.

ANALYSIS: In this text, Amos seems to reference tectonic activity that now understood as tectonic plate movements in this region. Amos 9:6 might be a reference to a tsunami with “He sends for the waters in the clouds. Then he pours them out on the surface of the land.” and the description of a volcano in” The Lord touches the earth, and it melts” lacks the expected reference to a mountain. Here Amos 8:8 sounds like an earthquake. But in the next verse, he says “I will make the sun go down at noon and darken the earth in broad daylight.” This could be the clouds of the Thera volcano or a solar eclipse. But the mixing of an eclipse and an earthquake is a less likely meaning, so I think it is more likely that Amos is talking about the Thera eruption.

2.--Revelations 8:8-9. (New International Version)
8 The second angel sounded his trumpet, and something like a huge mountain, all ablaze, was thrown into the sea. A third of the sea turned into blood,  9 a third of the living creatures in the sea died, and a third of the ships were destroyed.

In Revelations, seven trumpets are sounded. This is the second. Here a tsunami is implied by a huge mountain being thrown into the sea and ships being destroyed. Although the writer of Revelations was on the Island of Patmos (only 88 miles or 140 km from Santorini), it was written about 1700 years later (see Figures 1 and 2). But I think this passage by John of Patmos as a very remarkable summary of the Thera caldera collapsing into the sea and causing a mega-tsunami. However, we can not exclude this passage as being a reference to a more recent event at Mount Etna or the much older event at Etna when the Valle del Bove was formed 8300 years ago. So this could be an event that has happened more than once in the Mediterranean, and the geologic setting suggests that it will certainly happen again sometime in the future.

SUMMARY AND CONCLUSIONS

If we accept the traditional timelines given for the Bible and the dates scientifically determined for the Thera eruption, then this event occurred roughly 640 years before 2 Samuel 22 and Psalms 18 was written. An observer analysis made of this account indicates that it is a description of a volcanic eruption with a tsunami from the perspective of several independent points of view in time and distance. There are three or maybe four components of the Thera eruption known by scientific study that are included in the King David account: a tsunami, pyroclastic flow, lava bombs, and lava. Scientific studies also show that it was a Plinian eruption with a column of smoke that rose high in the atmosphere. We know that these eruptions darken the sky for days this also matches the 2 Samuel account and that by Amos. I think that David inadvertently helps to prove not only his existence but his kingdom by referencing the historic Thera eruption in detail because only he could have been in a position to hear these stories of this event (see his kingdom in figure 2 Part I of this blog).  When we consider the way 2 Samuel 22 was written starting and end with the language of a tsunami, we must also realize that it would have been a tsunami that would have affected the area of David's Kingdom and not so much the Thera eruption itself.

When we add up all the facts found in 2 Samuel 22, we find a virtual fingerprint of the Thera eruption 3800 years ago. This event is probably mentioned in the Bible numerous times so it was a well-known event up to the period when Revelations was written. But then it was lost in time until modern scientist re-discovered this event in the last 50 years. So the Thera eruption story as revealed in 2 Samuel is has been a story hidden in time for all these years. To me, this is truly remarkable and I think that this story helps to show that the Bible is a factual document certainly during the period of King David. 

Here are my own conclusions I have drawn from 2 Samuel 22 and Psalms 18:

1. The very minor changes made in Psalms 18 is an inadvertent validation of 2 Samuel 22 as being the exact words of King David. For here there is no question as to how the passage might have been changed by future editors.

2. Think there is an inadvertent validation here of King David and his Kingdom. He was just telling us a story that he heard from the people that were living in the northern part of his Kingdom, but in so doing the whole story becomes very real with the Thera connection.

3. The scientific story revealed here is not the purpose of the text. David is not trying to teach us about volcanoes. David saw God in all of nature. In the very next chapter of Psalms, he writes "The heavens declare the glory of God; and the firmament sheweth his handywork." I wonder if we are losing that with all our technology? I like technology, don't get me wrong, but from time to time turn it off and enjoy what God has made. During the time of David and far beyond there was no such thing as light pollution. So only a very few people today get to witness the night sky as these people saw it.

Related with the geologic environment of the Mediterranean volcanoes is plate tectonics. The concept (continental drift) for this was proposed by Alfred Wegener in 1915. An important part of this is to recognize that the surface of the Earth shifts, so maybe this aspect should be attributed to Amos in the Bible. Both Amos and Naham seem to refer to historical events and make projections about the future with that information. Amazingly this basic idea is what is done today. We study past earthquakes and volcanic activity to determine the risk for the future.

All of these accounts of the Thera eruption provide detail that was not previously known to science. There appears to be a continuous loss of detail about the event as it becomes more distant in the past. This indicates that the knowledge of the event in each case is being passed down orally. By the time we get to Amos and Nahum the story of Thea seems to be more diluted and also mixed in with other natural phenomena like an eclipse and earthquakes. This pattern breaks down with the vivid detail we find in Revelations. So I think this means that this might be a more recent event than Thera, but more likely it is a result of an older written account of Thera being incorporated into Revelations.


References

Barber, E.W. and Barber P.T. (2004) When They Severed Earth from the Sky - How the Human Mind Shapes Myth. Princeton Univ. Press.

Cita, M. B. and Rimoldi, B. (2005). Prehistoric mega-tsunami in the eastern Mediterranean and its sedimentary response. Rend. Fis. Acc. Lincei. Vol: 16:137-157.

Foster K. P. and Ritner R.K. (1996) “Texts, Storms, and the Thera Eruption.”  Journal of Near Eastern Studies 55 (1): 1–14.

Galili E., Horwitz L. K., Hershkovitz I., Eshed V., Salamon A., Zviely D., Weinstein-Evron M., and Greenfield H. (2008) “Comment on: Holocene tsunamis from Mount Etna and the fate of Israeli Neolithic communities" Geophysical Research Letters. Volume 35, Issue 8.

Goodman-Tchernov B. N., Dey H. W., Reinhardt E. G., McCoy F., Mart Y. (2009) “Tsunami waves generated by the Santorini eruption reached Eastern Mediterranean shores.” Journal Geology, vol. 37, no. 10, pp. 943-946.

Mastrolorenzo G., Petrone P., Pappalardo L., and Sheridan M.F. (2009) “The Avellino 3780-yr-B.P. catastrophe as a worst-case scenario for a future eruption at Vesuvius” Geological Society, London, Special Publications. 322 (1) 105-119.

McCoy F.W. and G. Heiken (2000) Tsunami Generated by the Late Bronze Age Eruption of Thera (Santorini), Greece,  Volcanic Hazards and Disasters in Human Antiquity, Geological Society of America, Special Paper No. 345: 43-70.

Milia A., Raspini, A. & Torrente, M.M. (2002) Evidence of slope instabilities and tsunami associated with the 3.5 ka Avellino eruption of Somma–Vesuvius volcano, Italy. Geological Society, London, Special Publications 01/2009; 322(1):105-119.

Pinker, Aron (2004) “Nahum’s Theological Perspectives” Jewish Bible Quarterly. Vol. 32, No. 3

Soloviev, S. L., Solovieva O.N., Go, C.G., and Kim, K.S. (2000) Tsunamis in the Mediterranean Sea 2000 B.C.-2000 A.D. Advances in Natural and Technological Hazards Research, Vol. 13. 237.

Stothers R. B. and Rampino M. R. (1983) Volcanic Eruptions in the Mediterranean Before A.D. 630 From Written and Archaeological Sources,  Journal Geophysical Research, 88, 6357–6371.

Taddeuci and Wohletz, (2001) Temporal evolution of the Minoan eruption (Santorini, Greece), as recorded by its Plinian fall deposit and interlayered ash flow beds. Journal of Volcanology and Geothermal Research, Volume 109, p.299-317

Vespa, M., Keller, J., and Gertisser, R. (2006) Interplinian explosive activity of Santorini volcano (Greece) during the past 150,000 years. Journal of Volcanology and Geothermal Research, Volume 153, Issue 3-4, p. 262-286.

Yokoyama, I. (1978), The tsunami caused by the prehistoric eruption of Thera. In Thera and the Aegean World II, Dumas, C., ed. London, Thera and the Aegean World, 277-283.

APPENDIX

A list of references to volcanic eruptions in the Bible. The number of times that a volcanic event is mentioned is shown in parentheses. Passages that also have a possible tsunami (looked at in this blog) are marked with an asterisk:

(2) Exodus 13:21, 19:18
(5) Deuteronomy 4:11, 5:4-5, 5:22-23, 9:15, 10:4
(1) Judges 5:5
(1) 2 Samuel 22:5-16*
(1) 1 Kings 19:11-12
(1) Nehemiah 9:19
(5) Psalm 18;4-15*, 83:14, 97:2-5, 104:32, 144:5
(2) Isaiah 4:5, 64:1-3
(1) Jeremiah 51:25
(1) Ezekiel 1:4
(1) Joel 2:10
(1) Amos 8:8-9*, 9:5-6
(1) Micah 1:4
(1) Nahum 1:5-6*
(1) Acts 2:19-20
(1) Hebrews 12:18
(1) Revelations 8:8*

Biblical Accounts of Volcanic Eruptions with Tsunamis-Part I of II

“something like a great mountain burning with fire was thrown into the sea. A third of the sea turned to blood, (9a) third of the living creatures in the sea died, and a third of the ships were destroyed.…” Revelations 8:8-9

This blog was updated on 8-14-2018,  6-18-2018, 12-25-2018, 3-24-2020, and again on 12-14-2020.
INTRODUCTION

There are at least 26 references in the Bible to smoking or melting mountains but there are only a few references that also include language that sounds like a tsunami. In an appendix at the end of this blog, I list all the Bible passages that seem to reference volcanoes. It is generally understood that volcanoes on the shore or islands can produce tsunamis, but only two known volcanic events, that happened before the Bible was written, may have produced tsunamis in the Mediterranean Sea. Connecting these events with the Bible was not possible until the last 40 or 50 years because the details of these eruptions were unknown until scientists investigated and dated them. This means that these Biblical accounts are references to recently discovered actual historical events and they provide the most detail of the Thera eruption (3600 years ago) from any source. This eruption, also known as the Minoan Eruption, was the most violent and the most catastrophic event known to science in the Mediterranean Sea. It also produced a mega-tsunami (40 meters) and the first known to science that was caused by a volcano. The Anak Krakatau (Indonesia) has produced 2 tsunamis one in 1929 and another on 12-22-2018 that killed over 400 people. During the 20th century tsunamis triggered by volcanoes occurred once every 3.2 years on average. Most have produced little damage but three between 1792 and 1883 killed over 10,000 people each. The worst was Krakatau that killed 36,000 in 1883.

The Bible is rarely referenced in volcanic research. Stothers and Rampino (1983) wrote: “like others, we find that Biblical and Egyptian literature is generally too sparse and too ambiguous concerning natural phenomena to be really useful and is applicable mostly to the period before ca. 700 B.C.” They discuss the Thera eruption but provide no literary accounts. Foster and Ritner (1996) looked more closely at possible Egyptian references of the Thera eruption. They used a datable text (Tempest Stela) that might be a reference to the effects of this cataclysmic eruption. However, these text expressions like “rain, darkness, louder than the cries of the masses” are much more ambiguous than the Biblical text that I will discuss. Surely the story of Thera was not excluded from the Bible, but if it is included where is it? Many have tried to make this connection before mainly by trying to connect the story of Exodus with this eruption. But if we accept traditional timelines for this period, we find that the Thera eruption occurred at least 150 years before the Exodus and before any dates proposed for the birth of Moses. Yet this event was so catastrophic that stories about it should have persisted for hundreds of years and eventually filter into Biblical text. I will show that this is exactly what happened. As I make these connections I only considered widely accepted Biblical dates and timelines.

TIMELINE OF MEDITERRANEAN VOLCANIC EVENTS AND BIBLICAL ACCOUNTS

Figure 1 shows a timeline of Biblical dates and period volcanic activity in the Mediterranean starting with the Thera and Avellino eruptions. The first passage I consider was written or edited
probably late in life by King David (1040-970 BCE). The second account I review was written by Nahum and it is thought that this book was written before 612 BCE when Nineveh was destroyed and after 663 BCE when Thebes in Egypt was destroyed. So David is writing roughly about 990 BCE and Nahum is writing sometime before 612 BCE. So we are looking for violent volcanic eruptions prior to these times that produced a tsunami. The Thera eruption apparently occurred between 1628 BCE and 1600 BCE. Radiocarbon dating places the eruption closer to the 1628 BC date. So the text of David was written roughly 640 years after the Thera eruption and the Nahum text was written roughly 350 years after the text of David and nearly 1000 years after the Thera eruption. The last account considered was written about 1700 years after Thera but only 190 years after an eruption at Mount Etna.

GEOLOGICAL SETTING

The Mediterranean and adjacent areas rank among the seismically most active regions of the world and are the second-largest source of tsunami around the globe. The reason for this seismicity is the collision between the African and the Eurasian tectonic plates. Besides seismicity there exist other sources for tsunami, such as volcanic eruptions and landslides. Tsunamis are created when a large amount of water is suddenly displaced by a geologic event.  A tsunami in the Indian Ocean in the year 2004 killed 227,898 people in 14 countries and another in 2011 killed 15,885 in Japan. These tsunamis were caused by earthquakes. But tsunamis caused by volcanoes have also killed thousands of people. The Thera and the Avellino eruptions are considered to be Plinian because they were similar to the eruption of Mount Vesuvius in AD 79. These powerful eruptions produce plumes of ash that rise up to 45 kilometers (28 miles) into the atmosphere. They are called Plinian because of a well-known written account of the AD 79 event by Pliny the Younger.

When I first started working on this, I thought that these Biblical accounts could have only been descriptions of the Thera eruption at Santorini Greece, I still think that is correct but there are other possibilities that should be considered. This includes the more distant and smaller Avellino eruption of the Somma-Vesuvio Volcano, Italy, and a third event at Mt Etna several thousand years before. However, in the last case, the tsunami might not have been produced by volcanic activity. So this event does not correlate well with the Biblical accounts that I consider. Continued study of ancient Mediterranean eruptions will certainly add to our understanding of these Biblical connections.

THE VOLCANIC CANDIDATES

1. The Thera eruption at Santorini occurred about 1000 kilometers (620 miles) from the eastern coast of the Mediterranean. According to radiocarbon dating, the Thera eruption occurred sometime over a 28-year span between 1628 and 1600 BCE. This eruption is believed to be the second or maybe the third largest in human history. To evaluate the size of an eruption, scientists compute the (DRE) dense rock equivalent of ejected magma, pumice, and ash. This eruption had a DRE of 60 cubic kilometers (14 cubic miles) of ejected material. It also created tsunamis mainly because it occurred on a small island out in the Aegean Sea that joins the Mediterranean Sea. Geologists have studied deposits made by the eruption and have pieced together what caused the related tsunamis. McCoy and Heiken (2000) describe 4 phases of the Thera eruption and explain how each could have produced tsunamis. This included large pyroclastic flows that encountered the sea and later when the caldera collapsed into the evacuated magma chamber below to create an island ring caldera and a mega-tsunami. In 1981 Kastens and Cita reported that “the collapse of the caldera of the volcano of Santorini caused a huge tsunami which is recorded archaeologically and geologically around the eastern Mediterranean.” The most comprehensive evidence that a tsunami from this eruption reached the Eastern Mediterranean coast came from a study by Goodman-Tchernov, B. N. et al. 2009. They found Thera age tsunami deposits at Caesarea Israel (see Figure 2) in offshore core samples. McCoy and Heiken (2000) estimated that the wave heights along coastal areas were about 7- 12 m based on other tsunami deposits. According to a University of Rhode Island press release:

An eruption of this size likely had far-reaching impacts on the environment and civilizations in the region. The much-smaller Krakatau eruption of 1883 in Indonesia created a 100-foot-high tsunami that killed 36,000 people, as well as pyroclastic flows that traveled 40 kilometers across the surface of the seas killing 1,000 people on nearby islands. The Thera eruption would likely have generated an even larger tsunami and pyroclastic flows that traveled much farther over the surface of the sea.

2. The Avellino eruption. The much wider time frame of this eruption overlaps that of the Thera eruption. Studies of this eruption show it occurred sometime between 1500 and 2000 B.C.E. and it was about 10 times smaller than the Thera eruption. It was also twice as far from the Eastern Mediterranean coast. The evidence for a related tsunami has been disputed. If there was a tsunami created by the eruption, the effects probably were limited to the area near the volcano. A group of researchers found evidence for a tsunami that affected the Bay of Naples. For the people living nearby, there were evacuations recorded as footprints in the volcanic ash. Mastrolorenzo, Pappalardo, and colleagues (2009), analyzed ash deposits and reconstructed the Avellino event in detail. This “ Plinian eruption produced an early violent pumice fallout and a late pyroclastic surge sequence that covered the volcano surroundings as far as 25 km away, burying land and villages. “

3. Mount Etna. This event seems to be a tsunami that may have been connected with volcanic activity of unknown magnitude. In 1996 Calvari and Groppelli attributed part of the Chiancone deposit (a volcaniclastic fan on the eastern flank of Mt. Etna) to a huge mudflow that may have been associated with an important eruptive event. In 2007 Pareschi et al. wrote “About 8.3 ka (8300 years) ago a devastating tsunami flooded the coasts of the Eastern Mediterranean Sea. That tsunami was triggered by a landslide from the collapse of the eastern flanks of Mt. Etna volcano... inducing a scar on the slopes, named Valle del Bove... The tsunami had a large impact, effecting... Lebanon and Israel. In Israel the tsunami-ravaged the Neolithic village of Atlit-Yam caused the death of villagers and animals...” The impact of this event on the coast of Israel was disputed by Galili et al. (2008).

Other events occurred near Mt. Etna after the Prophetic Books of the Hebrew Bible were written, but before the New Testament and the book of Revelations was written. These events occurred between 425 and 122 BCE (see Figure 1). The nearby Vucanello volcano was active during this period and built a new island, but there are no known tsunamis associated with this activity.

THE BIBLICAL ACCOUNTS OF VOLCANOES WITH TSUNAMIS

Figure 2 shows a map of the Eastern Mediterranean Sea showing the locations of places mentioned in these Biblical accounts. It also shows how the tsunami could have propagated eastward and the

Figure 2. Map of the Eastern Mediterranean Sea showing locations
of Biblical references made by Nahum, David's Kingdom, the island
of Patmos and the Thera volcano. Contours show tsunami distance-
arrival times by Yokoyama, 1978.

location of Caesarea where offshore tsunami deposits were found. The following passages are from the New International Reader’s Version of the Bible. It is interesting to read different versions of this passage. This version seems to describe the tsunami better than others. The most detailed account is also the oldest account and closer in time to the Thera eruption.

1.-- 2 Samuel 22; 5-16 NIRV (also Psalm 18: 4-15).

5 The waves of death were all around me. A destroying flood swept over me. 6 The ropes of the grave were tight around me. Death set its trap in front of me. 7 When I was in trouble I called out to the Lord. I called out to my God. From his temple he heard my voice. My cry for help reached his ears. 8 The earth trembled and shook. The pillars of the heavens rocked back and forth. They trembled because the LORD was angry. 9 Smoke came out of his nose. Flames of fire came out of his mouth. Burning coals blazed out of it. 10 He opened the heavens and came down. Dark clouds were under his feet. 11 He got on the cherubim and flew. The wings of the wind lifted him up. 12 He covered himself with darkness. The dark rain clouds of the sky were like a tent around him. 13 From the brightness that was all around him flashes of lightning blazed out. 14 The LORD thundered from heaven. The voice of the Most High God was heard. 15 He shot his arrows and scattered our enemies. He sent flashes of lightning and chased the enemies away. 16 The bottom of the sea could be seen. The foundations of the earth were uncovered. It happened when the LORD's anger blazed out. It came like a blast of breath from his nose. 17 “He reached down from heaven. He took hold of me. He lifted me out of deep waters. 18 He saved me from my powerful enemies. He set me free from those who were too strong for me.

ANALYSIS:  This passage as written in Psalms is one of the theophany events of the Bible. According to the Dictionary of Bible Themes, a theophany is a visible manifestation of God that may also be a natural phenomenon.  I will attempt to show that this passage is actually a recently discovered but a well known and established historical event. The possible references to a tsunami are: (5) “ The waves of death were all around me. A destroying flood swept over me. ”; (12-other translations) “gathering of waters”, and (16) “The bottom of the sea could be seen.” Seeing the bottom of the sea must be a tsunami. In 2004 a 10-year-old girl saved the lives of almost 100 tourists when she recognized the approaching tsunami as the sea receded. References with a volcano are more self-evident but there are added elements like “lightning” that occurs in the smoke of larger Plinian volcanic eruptions and possible pyroclastic flows in (10) “ Dark clouds were under his feet.” Taddeuci and Wohletz, (2001) reported that the pyroclastic deposits of the Thera eruption are well documented in the volcanological literature. In this text, there are references to lava or volcanic bombs in verses 9 “Burning coals blazed out of it” and 13. In verse 13 (other translations) lava bombs are expressed as “coals of fire flamed forth.”  Barber and Barber (2004) show a photo of a Minoan structure at Akrotiri (Santorini) destroyed by a large lava bomb from the Thera eruption.

This is an eruption that we know about only because of recent scientific studies. So far we know that it produced pyroclastic flows, lava bombs, and a tsunami that all match this Biblical passage. Is there any other passage in the Bible that provides this kind of detail of an event established through scientific studies? 

I remember the first time I read Psalm 18 nearly forty years ago. Over the years I re-read this and each time my curiosity deepened. What first struck me is that this passage clearly contains the language of a significant volcanic event and there is much more detail than we typically see in other Biblical passages. But what volcanic event is King David talking about? Was he a witness to this event or did it happen before his time? As I attempted to answer these questions, I discovered the nearly parallel text in  2 Samuel 22 with a slight change in wording that results in a very significant addition of a deadly tsunami to the volcanic event. Now, this biblical event has even more detail, making it more possible to match the passage to a known volcanic event - one that caused a tsunami!

To me, the most important aspect of this whole passage only seen in 2Samuel is that the description of the volcano is wrapped (beginning and end) with the description of the tsunami ("waves of death" and "the bottom of the sea could be seen". This clearly connects the volcano and the tsunami. The tsunami would have created the largest impact from this event on the eastern shore of the Mediterranean Sea and this part of the story is emphasized in the passage. This fact strongly connects this volcanic event with this passage.

To best understand this passage I have performed an observer analysis that considers the location of the observer and the chronology of the observation. This shows whether the whole story is one of a single observer or a collection of observations made by more than one person. We must also understand that these are ancient descriptions made of an eruption. The people that experienced this event did not have a modern language with words we use today to explain this kind of event. There was no word for tsunami, volcano or lava or any pyroclastic material. The result is a description of a volcano and a tsunami made without any of the words of a modern language to describe these events.

Let's begin with verse 16: “The foundations of the earth were uncovered.” I think that if you walked across a desolate land recently covered with lava or ash you might conclude that the ground is not ordinary and that it might be ground underneath the normal surface of the earth and that you might describe this in this way. This part of the story is produced by the understanding that the normal rock, sand, or soil normally seen on the surface of the Earth is missing.  If this is correct then this is most likely a description of the land made long after the event when people began to go back into the area. Also to survive the “mega-tsunami” produced by this eruption you would most likely be hundreds of miles away from the volcano, maybe too far away to see the lightning and the pyroclastic flows, and certainly too far away to see lava bombs. So these verses seem to be mixed descriptions of a volcanic eruption from the point of view of someone far away caught in the tsunami, someone else close enough to see lightning,  pyroclastic flow, and lava bombs, and thirdly someone that saw the land long after the event occurred. So I conclude that this whole passage is a collection of stories from different people about the tsunami and the volcano.

From reading these passages we might conclude that King David was a part of this terrible event, which is certainly a possibility, but there is no known volcanic event during his life (see the timeline in Figure 1). I list 5 possible passages about volcanoes (see appendix) in Psalms, but if David had actually been a part of this event, I think he would have had even more to say about it. It seems most likely that David heard the stories of this eruption that were passed down from survivors and he then parallels this event with and his own life struggles and his relationship with the Lord. This passage includes at least 3 different points of view indicating that it is a collection of stories. If we assume that this is the Thera eruption, we can see David comparing the story of Thera with his own story in verses 17 and 18. Verse 18 has no reference to the event in question but I included it because it shows this context for the other verses. David compared with other Biblical writers had a unique advantage to hear stories of past events as a ruler of a large part of the Eastern Mediterranean. His kingdom as described in earlier passages in 2 Samuel is shown in Figure 2. Also seen in this map is the probable propagation of the Thera tsunami on the Eastern shore of the Mediterranean Sea and the land that King David ruled.

David references this eruption again in Psalm 97: 2-5, Psalm 104:32, and Psalm 144: 5-7. In Psalm 97 he repeats the reference to lightning in verse 4 and adds a reference to lava in verse 5 with “The mountains melt like wax.” There had to be lava to produce lava bombs as we saw in 2 Samuel 22. But in this case, there is no reference to a tsunami but in Psalm 144: 7 he cross-references this event with the phrase “rescue me from the mighty waters.” This phase is repeated from 2 Samuel 22:17 and Psalm 18:16.

Lastly, I must ask the question: Why are there two slightly different versions of this event in the Bible?  Did David or his writer make two versions of the same story and just change a few words or is the result of later editing? In some commentaries, it is suggested that 2 Samuel was the original version. If this is a collective account of the Thera eruption then the 2 Samuel version provides more detail of that event. Note that in the 2 Samuel account “chords of death” is replaced by “waves of death”.  If you Google “waves of death” you find a documentary of the disastrous 2004 tsunami and this 2 Samuel account. There is a great deal more information about this event in this account than anywhere else in the Bible or any other text that I know about.

In part II of this blog, I will look at other possible accounts in Nahum, Amos, and Revelations and then provide a summary and conclusion. I will talk more about 2 Samuel 22 in that conclusion.

The Origin of Hogwallows and Gilgai Landforms - PART II

You can scroll down to see my most recent blogs including Part I of this blog or you can click on this link:

The Origin of Hogwallows and Gilgai - PART II10/31/2013. This is a closer look at a theory I published in 1994 to explain these landforms. Included in this blog is a great photo of gilgai at ground level taken from Google Street View in Waxahachie Texas. This post was updated on 12/4/2018 and again on 2/2/2024 and 12/24/2024.

PREBUCKLING STRESS AND DIFFERENTIAL REBOUND IN OVERCONSOLIDATED EXPANSIVE CLAYS

It may be that there has been some confusion about what buckling is and how it is applied in this case. Generally, buckling is a deformation produced by a vertical axial load. It may happen in a linear member like a column or in a flat plate that is loaded in compression around the edge of the plate. In the first case, the load is axial. There is a critical load at which buckling produces a deformation. However, before the critical buckling load, there are internal stress changes that are the result of the applied load. These changes are magnified as the load builds up to failure. In this section, we will look at these pre-bucking changes in stress. It is important to understand the difference between a pre-buckling load (axial) that is not critical and a critical buckling load. The internal stresses associated with critical buckling do not just suddenly appear when the load becomes critical. So before a critical buckling load, the normal internal stresses are altered. Expansive soils are load-reactive ie, they react to changes in confining (vertical) pressure. That is they swell more with less confining pressure and swell less as the confining pressure increases.

A deeply buried expansive soil will not expand if the confinement pressure (from the weight of the soil above) equals or is greater than the expansion pressure. I call this depth the "rebound depth."As this confining pressure is decreased, the clay can expand more and more. The key idea is that before a critical buckling load, there are internal changes in stress that alters the normal confining pressure (in the horizontal direction) that then triggers differential vertical rebound. Where mounds will appear the normal confining pressure is decreased and where depressions will occur the normal confining pressure is increased. These internal changes in stress, less than the critical buckling load can trigger differential heave and create the appearance of buckling. The evidence that gilgai are not caused by a critical buckling load are:

1. Farmers who have plowed gilgai flat report that gilgai will reappear in a few years this is supported by Goggle image histories of specific gilgai sites. I.e. if the movement rate is more like normal shrink-swell movements, then this is not a critical (sudden) buckling issue.

2. Gilgai only occurs in expansive soils. If critical buckling was involved it would happen in other clays like Kaolinite, Illite, and Chlorite.

So this means that the normal shrink-swell behavior of expansive clays appears to be the energy that is creating the gilgai. If you were to place some heavy lead plates on the ground in a pattern resembling gilgai depressions, in a few years there would be a differential rebound that would mimic gilgai with the plates in the depressions. In this case, K_o >1 had nothing to do with the movement. However, K_o >1 but less than the critical buckling load can take the place of the lead plates. This is because an elastic member can carry a significant axial load up the critical buckling load but not without reacting to the load internally. This is what I call pre-buckling. When this happens expansive soil senses a change in vertical load just like there were lead plates on the surface of the ground. So in one sentence K_o >1 and shrink-swell behavior work together to produce differential rebound. I think we can say that once the buckling load represented by K_o approaches 25 to 50% of the critical buckling failure load then differential heave kicks in to create gilgai. But that is just a guess as to those percentages. The true analytics of the problem are quite complex because there are a lot of related properties that change with depth such as K_o, expansion potential and soil strength and others.

I will now show you in more detail how this works using a simplified model constructed from a long strip of elastic material that has self-weight and can buckle like a continuous sine wave. Think of this as a heavy very long column (an axially loaded member) that is lying down. It is fully braced in the z-direction (in and out of the page) due to self-confinement. Oddly, in this case, the material self-weight helps to brace the column, so for true buckling to occur it has to overcome the buckling strength of the material and it also has to lift the material as well. However, there is a lifting influence before the critical buckling load.

I zoom in to look at a random segment of this longer strip in Figure 2. I have made several simplifications to show what happens internally and more importantly how the weight of the material is supported at the base of the material. A technically correct drawing would have roller supports along the sides and below. I have removed these for clarity. This drawing shows three levels of K_o in the material. This is the ratio of horizontal stress with the vertical stress. In the first drawing, the model has K_o =1 the horizontal loading on the side matches the weight of the material. In the second drawing K_o =Kcr (the critical buckling load) and the strip of material has buckled due to the higher horizontal loading. We don't know the actual value of K_o in this case, but we assume it is higher than the Rankin failure I show in Figure 1. So in this 2nd case, the material is a stronger material than a clay deposit for this behavior to occur. In the third drawing, there is less horizontal load but it is still higher than the vertical (self-weight due to gravity). Although the load is not high enough to produce buckling, changes in the internal stress are still there. You could say that the material it trying to buckle and producing a differential load (see support reactions) on the subsurface layers. This should trigger a differential rebound that would only occur in an expansive soil. The effect is the same as if you placed some heavy lead plates in locations of future depressions.

HOW MOUNDS TRANSFORM INTO MICRORIDGES (POLYGONS)

Figure 3 shows how mounds and depressions (a) change into more commonly seen polygon (c) shapes. My photo in PART I shows gilgai that are in transition (b) in-between. In mature gilgai, mounds are replaced by interconnected micro-ridges to create polygons. If you look at the aerial image at location (32.419913,-96.77876) dated 2-27-2001 you can see better developed polygonal gilgai in the yard behind the house. You can also see where contours have been plowed through the gilgai to help retain water and where the gilgai have been plowed flat in adjacent fields.

In 1994 I defined the term "shear joint" to describe the special subsurface fracturing that forms around gilgai mounds and micro-ridges. In the literature, you find these joints also called slickensides. However, the term slickensides has been used to describe lots of different shiny surfaces with different origins.  This is a special kind of fracture related only with gilgai and I think a special name should be used for these fractures. In Jackson Mississippi, I have seen shear joints that indicate that gilgai existed thousands of years ago and were eroded away leaving only the shear joints as remnants of gilgai. Joeckel (1999) calls this kind of fracture synformal slickensides. Williams et al (1998) excavated two sections through gilgai and described the subsurface fractures. These are the best descriptions I have seen for subsurface gilgai fractures.

The key concept of this final part of this theory shown in Figure 3 is that once mounds and depressions develop there is a slight loss of horizontal self-confinement. This then promotes additional lateral movement toward the mound. This squeezes the mounds into narrow ridges that eventually connect to create a continuous micro-ridge system or polygons. The development of shear joints around the perimeter of the mounds enables additional horizontal movement. The formation of linear gilgai on slopes occurs for the same reason that polygons form; the slope allows downhill creep to occur, this releases self-confinement in the downhill direction. This means that K_o >1 becomes directional occurring only perpendicular with the slope. This also means that K_o >1 is providing some of the energy into downhill creep that is well known in expansive clays. The very existence of linear gilgai proves that there are strong horizontal forces that are behind the formation of gilgai.

Mound squeezing explains several phenomena associated with gilgai mounds. Some of these are:

1. Tightly wrinkled shear joints inclined at steep angles under the mound perimeter. A photo of this can be seen in Figure 3-32 in Chapter 3 of the Soil Survey Manual. They do not relate these fractures with gilgai but these look the shear joints I have seen in the local Yazoo clay. Another image of this can be seen in Joeckel(1999). 

2. Features called chimneys where the subsurface strata appear to be pushed up under the mounds. These features have been compared with diapirs (Gustavson 1975).

Nature "turns off" or switches off gilgai when the K_o >1 soils become too deep or when expansive soils are replaced with non-expansive soils. This means that when you see a large field with polygons (c) around the perimeter you will occasionally see less mature forms (a) or (b) where nature is preventing the mature forms from developing. The transition is most often represented by the micro-ridges being wider. My guess is that this is most often happens when K_o >1 soils are buried by soils where K_o is equal to or less than one. Because the rate of erosion is slow, there is no reason for gilgai to be actively forming, at least in the southeastern United States unless surface soils have been removed by human activities and elevated K_o >1 expansive soils nearer to the surface. When we see the less mature forms of gilgai it shows that there is not enough expansive energy to push the gilgai into the mature stage.

The development of salt polygons in desert environments appears to occur by an almost identical process as I describe here, except in the case of salt polygons the horizontal force is maybe produced by the growth of salt crystals (see the textbook Geomorphology of Desert Environments (2009). This parallel process may be the best supporting evidence for K_o >1 theory of gilgai. 

Surface cracks vs Ko>1 theory

Surface cracks over gilgai mounds are a secondary effect produced by clay weathering, the deformation of the soil, and the release of horizontal stress near the surface that results from these processes. Self-mulching is also a secondary effect caused by erosion of surface material on top of mounds into the depressions. So the gilgai has to be developing or already present for these secondary effects to occur.
1. Surface cracks or shrinkage theories (this includes self-mulching)can't explain linear gilgai and those with polygonal shapes because the scale of gilgai never matches the scale of ordinary shrinkage cracks in a map view. Shrinkage cracks that form over gilgai mounds are not ordinary and are only seen after the appearance of gilgai and never before. Wavelengths of gilgai vary from about 12 to 30 feet. Shrinkage cracks formed in mud are usually less than 1 foot apart. Desiccation polygons that form in playas in the western U.S. appear at scales much larger than gilgai. For shrinkage crack theory to be valid there needs to be examples of large areas of shrinkage cracks at the same scale as gilgai. This does not exist.

2.  If gilgai resulted from surface cracks, it could be established by mapping the surface cracks as related to the topography or maybe by filling cracks with soil or by running water in the cracks in the field or by correlating moisture content with cracks. These kinds of studies have not shown correlations that support these theories. Two examples are Spotts (1974) and Kishne, Morgan and Miller (2009).

3. Surface cracks theories were proposed from 1840-1930 before modern soil mechanics discovered that horizontal stress naturally occurs in overconsolidated expansive clays. I think this negates these awkward attempts to generate horizontal thrust with a shrinkage crack.

4.  Shrinkage crack theories would not function under pavements, and pavement undulations have been associated with gilgai in several studies.

5.  Not all gilgai have surface cracks. Two sites in the Bienville National Forest in Mississippi don't have shrinkage cracks even during drought conditions. What causes these gilgai?

6.  The Ko>1 origin of gilgai can create gilgai of all forms with or without surface cracks. This is the only gilgai theory discussed in a peer-reviewed engineering journal. There are no valid published criticisms that have not been answered since this theory was introduced in 1994. l would be happy to respond any questions or criticisms.

7. The Ko>1 condition is well established in overconsolidated clays, if in the special case of expansive clays, that gilgai are not produced, then what does happen? How could an expansive clay ignore the presence of Ko>1 instability without reacting in some way that is out of the ordinary?

A FEW FINAL THOUGHTS

If you want to see gilgai in the field based on Google Earth images, you must realize that gilgai you see in aerial photos may not always be visible on the ground. The relief is typically less than 1 foot so if the grass or brush is higher than 1 foot, you may not be able to see the gilgai on the ground. So you need a fresh mowed field, yard or an actively used pasture to see gilgai on the ground. Your best bet is a pasture or land that is mowed regularly. Also occasionally owners plow the gilgai flat. In this case, the gilgai may come back but you may have to wait a few years. If you find this subject interesting and wish to read more please check out Riddell's two publications. His hogwallow descriptions are most interesting. I don't think his work has ever been referenced in recent gilgai research, so his work is herein being brought back in the history of gilgai research. Also, the paper by Mayne and Kulhawy is considered to be a classic in geotechnical engineering.

REFERENCES:

Gustavson, T. C. (1975). "Microrelief (gilgai) structures on expansive clays of the Texas coastal plain--Their recognition and significance in engineering construction." Bur. Econ. Geology--Geological Circular No. 75-7, University of Texas, Austin, Tex.

Hilgard, E. W. (1906). "Soils" New York, The Macmillan Company. 593 p.

Howard, A. (1932). "Crab-Hole, Gilgai and Self-Mulching Soils of the Murrumbidgee Irrigation Area" Pedology (Pochvovedeni), p.14-18.

Joeckel, R.M. (1999). " Paleosol in Galesburg Formation (Kansas City Group, Upper Pennsylvanian), Northern Midcontinent, U.S.A.: Evidence for Climate Change and Mechanisms of Marine Transgression." J Sedimentary Research. Vol. 69, No.3, p720-737.

Kishne, A. S., Morgan, C. L. S. and Miller W.L. (2009) "Vertisol Crack Extent Associated with Gilgai and Soil Moisture in the Texas Gulf Coast Prairie" SSSAJ: Vol. 73: No. 4. p. 1221-1230.

Maxwell, B. (1994). "Influence of Horizontal Stresses on Gilgai Landforms." J Geotech Eng., ASCE 120:1437–1444.

Mayne, P.W. and Kulhawy, F.H. (1982). "Ko-OCR Relationships in Soil." J Geotech Eng. ASCE 108 No. GT6:851-872.

Michalowski, R. L. (2005) "Coefficient of Earth Pressure at Rest." J Geotech Geoenv Eng., ASCE 131:11, 1429-1433.

Riddell, J.L. (1839) "Art. II.- Observations on the Geology of the Trinity Country, Texas. The American Journal of Science and Arts, Vol. 37, Nov., p. 211-217.

Riddell, J.L. (1840) "37. Hog Wallow Prairies.*--Extract of a letter to the Editors…May23, 1840." The American Journal of Science and Arts, Vol. 39, Oct., p. 211-212.

Spotts, J.W. (1974) "The role of water in gilgai formation." P.H.D. Dis. Texas A&M University, College Station, TX.

Williams, D. Wilding L., Lynn, W. Kovda, I. and Chervenka, G. (1998) "Slickenside arrangement in Burleson clay - a udic haplustert" 16th World Soils Congress. Vol.1, p. 89