It would seem to everyone an understandable and ordinary question - why does the swamp suck in? In fact, this process is not as simple as it seems, and perhaps you will learn something new for yourself. First, the swamp that is sucked in is called a bog. It is capable of pulling only living objects. The bog is formed on the basis of lakes overgrown with a green carpet of moss and algae, not in all bogs.
The emergence of a swamp is facilitated by 2 reasons:
… overgrowth of a reservoir or waterlogging of land. The bog is characterized by excessive moisture, constant deposition of not completely decomposed organic matter - peat. Not all swamps are capable of sucking in objects, but only those in which the bog has formed. A bog is formed on the site of a lake. Lilies, water lilies and reeds on the surface of the lake grow over time into a dense carpet on the surface of the reservoir. Along with this, algae grow at the bottom of the lake. As it forms, a cloud of algae and moss rises from the bottom to the surface. Due to the lack of oxygen, rotting begins, organic waste is formed, diverging in the water and forming a bog.
Now let's move on to the suction process itself …
The bog sucks in living objects. This is explained by its physical properties. The bog belongs to the class of Bingham fluids, physically described by the Bingham-Shvedov equation. When lightweight objects hit the surface, they behave like solids, so the object will not sink. When an object is heavy enough, it sinks.
There are 2 types of diving: undersubs and oversubs. The behavior of a body trapped in a liquid is governed by the ratio of the effects of gravity and the buoyancy force of Archimedes. The body will sink into the quagmire until the strength of Archimedes is equal to its weight. If the buoyant force is less than the weight, then the object will be undersubmerged, if it is greater, then the object will be overloaded.
Why are only living objects subjected to overloading? This is because such objects are constantly moving. What if you freeze? Will the dive stop? Alas, this will only slow down the immersion, because a living body is always moving, as it breathes. Inanimate objects remain motionless, therefore they do not completely submerge. Over-immersion in the bog is the suction of the bog. Why does the movement of the body accelerate the dive? Any movement is the application of a force that increases the force of pressure on the support. It is due to the weight of the object and the force of gravity. Sharp movements are the reason for the formation of areas of low pressure under the body. These areas will lead to an increase in atmospheric pressure on the living object, which will further submerge it.
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Therefore, the physical definition of the word "swamp suction" looks like this: the Bingham liquid (bog), tries to transfer the living object that has got into it to a level below normal immersion, at which the Archimedes force is less than the body. The suction process is irreversible. A sunken body, even after the cessation of vital activity, will not emerge.
In addition to theoretical interest, the study of physical processes occurring in a swamp is of practical importance: many people die in swamps who could have survived if they were better aware of the insidious properties of the bog. And these properties are really very insidious. The bog is like a predator. It reacts differently to living and nonliving objects falling into it: it does not touch the dead, but sucks in all living things. This property of the bog deserves special attention and will interest us in the first place. First, let's describe it in more detail.
As a first approximation, a bog can be considered a liquid. Therefore, the bodies trapped in it must be acted upon by an Archimedean buoyancy force. This is true, and objects of even high density, exceeding the density of the human body, do not drown in a quagmire. But as soon as a person or other living creature gets into it, they will be "sucked in", that is, they will completely plunge into the quagmire, although their density is less than the density of objects not drowning in the quagmire.
Why does the quagmire behave in such an unexpected way? How does she distinguish living objects from non-living ones?
To answer these questions, we will have to dwell in more detail on the study of the physical properties of the bog.
About floating bodies in Newtonian fluids
Consider how a body floats in Newtonian fluids, for example, in water. Let us bring a body whose density is less than its density to the surface of the water, and let it go. After some time, a state of equilibrium will be established: the body will be submerged to a level at which the Archimedean buoyant force is exactly equal to the body's weight. This state of balance is stable - if the body is acted upon by an external force and drowned deeper (or, conversely, raised up), then after the cessation of the action of the force, it will return to its previous position. The level of immersion at which the Archimedean force is equal to the weight will be called the level of normal immersion.
Please note that the normal immersion level is determined only by the density ratio and is independent of the viscosity of the fluid. If the bog were just a Newtonian fluid with a high viscosity, it would not be very dangerous. With reasonable behavior, it would be possible to stay on its surface for quite a long time. Remember how tired swimmers behave if they want to relax right in the water? They roll over on their backs, spread their arms and lie motionless as long as they want. Since the density of water is less than the density of the bog, then in a similar way it would be possible to lie on the surface of the bog for a long time, and the viscosity would not particularly interfere with this. It would be possible to slowly think over the situation, make the best decision, try to carefully row with your hands, trying to get to a hard place (here the viscosity would be a hindrance),finally, just wait for help. The buoyancy force would reliably keep the person on the surface of the swamp: if, as a result of a careless movement, a person would plunge below the level of normal immersion, the Archimedean force would still push him back.
Unfortunately, the reality is much worse. A person who has fallen into a quagmire has no time either to think or, moreover, to wait. The quagmire is a non-Newtonian fluid and its Bingham properties change the situation drastically.
On the floating of bodies in Bingham fluids
Let us bring the body to the surface of the Bingham fluid and lower it. If the body is light enough and the pressure exerted by it is small, then it may happen that the stresses arising in the fluid will be less than the yield threshold and the fluid will behave like a solid. That is, the object can stand on the surface of the liquid and not submerge.
On the one hand, this seems to be good. It is thanks to this property that all-terrain vehicles with low ground pressure can easily overcome swamps impassable for humans. Yes, and a person, with the help of special "swamp skis" or wet shoes, can reduce the pressure on the soil and feel relatively safe in the swamp. But this phenomenon has another side. The very fact that the immersion of the body stops in the presence of inequality of weight and Archimedean force is alarming - everything does not happen as usual. Let's imagine that the weight of our body is large enough and it begins to sink. How long will this dive take place? It is clear that it is not up to those when the Archimedean force is equal to the weight. When the body is immersed, the Archimedean force will partially compensate for the weight, the pressure on the soil will decrease and the moment will come,when the stresses become less than to again. In this case, the Bingham fluid will stop flowing and the body will stop before the Archimedean force becomes equal to the weight. Such a state, when the Archimedean force is less than the weight, but the body does not submerge further, is called the undersubmersion state (see Fig. A).
A. is now the most important thing. If undersubmersion states are possible in a liquid, then, for the same reasons, oversubmerging states are also possible, in which the Archimedean force is greater than the weight, but the body does not float (Fig. C). Remember what happened in a non-Newtonian fluid? If, as a result of any actions, a person fell below the level of normal immersion, then the Archimedean force became greater than the weight and returned it back. In a Bingham fluid, nothing similar (for a sufficiently large τ0) occurs. Having submerged as a result of any careless action, you will no longer float back up, but will be in an overloaded state. The process of "drowning" in the quagmire turns out to be irreversible. Now you can give a more precise meaning to the word "suction". It means the desire of the quagmire to drown living objects below the level of normal immersion - into an oversubmerged state.
There is very little left for us - to figure out why the swamp bog sucks in, that is, it drags only living objects into an overloaded state.
Reasons for overdiving
Living objects are overloaded because, once in a quagmire, they move, that is, they change the relative position of their body parts. This leads to overloading for four reasons.
The first reason. Imagine that you have a heavy load in your hands and begin to lift it. To impart upward acceleration to it, you must act on it with a force greater than the weight of this body. In accordance with Newton's third law, the force acting on your hands from the side of the load will also be greater than its weight. Therefore, the force with which your legs press on the support will increase. If you are standing in a quagmire, then trying to lift the weight that you are holding in your hands will cause your feet to sink deeper into the quagmire.
And if there is no load in your hands? This does not change the fundamental aspect of the matter - the hand has mass, and therefore is itself a load. If you are at a normal immersion level, trying to simply raise your arm will lead to overdiving. In this case, the overloading will be very insignificant, but it will be irreversible, and repeated movements can lead to overdiving by a large amount.
The second reason. The bog is very sticky and in order to tear, for example, a hand from the surface of the bog, you need to apply force. In this case, the pressure on the support increases and overloading will occur.
The third reason. The bog is a viscous medium and resists moving objects in it. If you try to pull out a stuck hand, then as it moves, you will have to overcome the forces of viscosity, and the pressure on the support increases. Overloading will occur again.
The fourth reason. Everyone knows very well that when pulling a foot out of the mud, a characteristic squelching sound is heard - this atmospheric air fills the footprint left by the foot. Why do you think this sound is not heard when you pull your leg out of the water? The answer is quite obvious - water has a low viscosity, flows quickly and has time to fill the space under the leg moving up. Dirt has a much higher viscosity and forces that prevent the movement of some layers relative to others, more for it. Therefore, the mud flows slowly and does not have time to fill the space under the foot. There a "void" is formed - an area of low pressure, not occupied by soil. When you pull your foot out of the mud, this area communicates with the atmosphere, air rushes into it, and as a result you hear the same sound that we talked about earlier.
Thus, the presence of a squelching sound indicates that when trying to free a leg stuck in the mud, you have to overcome not only the forces due to stickiness and viscosity, but also forces associated with atmospheric pressure.
With sudden movements of a person caught in a quagmire, areas of low pressure will appear under the body parts moving in the quagmire, and atmospheric pressure will press down with great force on the person, pushing him into an overloaded state.
The combined action of all four causes leads to the following effect: a change in the shape of a body trapped in a bog leads to its overloading.
Much has now become clear. When inanimate bodies fall into the bog, they do not change their shape and there are no reasons for their overloading. Such bodies are not sucked in by the quagmire; once they are in the quagmire, they will remain in a state of undersubmergence. And living beings, once in a quagmire, begin to fight for their lives, flounder, which immediately leads to their overload. This is “suction”. The answer to the question posed at the very beginning has been received. However, this is not enough. How, then, to be saved, how to use the results of this examination to develop practical recommendations for those who have fallen into a quagmire.
Alas, much less has been done in this direction than we would like. If you do not consider the fantastic and semi-fatastic projects ("instantly inflating balloon that pulls a person out of the bog," "substance that causes the hardening of the swamp"), then the situation looks bleak.
How can you get out of the quagmire?
The main rule that everyone needs to know is not to make any sudden movements when in a swamp. If it is sucked into the swamp slowly, there is every chance of escape. Firstly, once in a swampy area, you need to get a stick, it is desirable that it be wide and strong, that is, a real block. This stick can be your salvation, so you need to choose it carefully, and not take the first twig that comes to hand. If you fall into a swamp, slipping off a bump, then you will most likely be sucked in quickly, since by inertia you will continue your movement, thereby helping the bog, so it is better to fall on your stomach or back, so you will be sucked much more slowly.
If you do not go under water too quickly and you have a stick, then it should be carefully placed in front of you, well, if the nearest stronghold is not more than half a meter, then the end of the stick will fall to the ground and it will be easier for you to get out. But even if the stick is completely in the swamp, you need to grab onto it and try to transfer your center of gravity to this stick, so you get a kind of bridge and you can get out on land or wait for help without risking finally going into the mud.
If you have absolutely nothing close at hand to leverage you, try to be horizontal. Do this as carefully as possible, carefully moving your center of gravity from your feet to your body, if you manage to do this, then your body weight will significantly decrease and you will no longer be pulled into the swamp. In this position, you can wait for help. But, being in a swamp, in no case should you make sudden movements, wave your arms and try to pull your legs, this will suck you even more into the abyss.
Those in this position should not even shout loudly, calling for help, and even more so swing their free limbs. If the top of your body is still free, then you need to take off your jacket or raincoat and throw it on the surface of the swamp, you can also get out along it, it will not allow the swamp to suck you in.
If it sucks into the swamp very quickly, then only a stranger can help, he must throw a rope or a stick, along which a person who has fallen into the swamp could get out onto a solid surface. Sometimes, in order to pull one person out of the swamp, at least three people are required on land, since the suction force at the swamp is very high. It should also be remembered that if a person is pulled out of the swamp, then in no case should he be released in order to take a break, a slightly released person will instantly go into the bog, receiving additional energy from the land when pushed off. The rescue activity must be active and without delay. Then success will be assured.
What else can the swamps tell us?
There is such a phenomenon as peat tanning - a kind of state of a corpse that occurs when a corpse enters peat bogs and soils containing humic acids. Peat "tanning" can also be called one of the types of natural preservation of the dead body. A corpse in a state of peat "tanning" has a dense dark brown, as if tanned skin. Internal organs decrease in volume. Under the action of humic acids, mineral salts in bones dissolve and are completely washed out of the corpse. Bones in this state resemble cartilage in consistency. Corpses in peat bogs are well preserved indefinitely, and when examining them, forensic doctors can determine damage sustained during life. Although such cases are quite rare, sometimes finds in peat bogs can present various surprises to researchers.
There are scary swamps on our planet, famous for their creepy, but historically priceless finds. We are talking about the "swamps of human organs" in Germany, Denmark, Ireland, Great Britain and the Netherlands.
Probably the most famous of the bog mummies is the Tollund Man, whom two peat collectors stumbled upon in May 1950 near the village of Tollund in Denmark.
They were cutting the peat into briquettes, when suddenly they saw a face looking directly at them and, thinking that this was a victim of a recent murder, immediately contacted the local police.
A short time later, radiocarbon dating of the hair of the Tollund man showed that he died around 350 BC. e.
Another ancient Dane with perfectly preserved hair was found in 1952 in a swamp near the town of Groboll. Judging by the cut throat, the poor fellow was killed and thrown into the swamp.
Well, the severed skull of the so-called man from Osterby, found in a swamp near the German village of the same name, gives an idea of what hairstyles were worn by elderly men in the ancient German tribes that lived on the territory of the FRG in the first millennium BC. This hairstyle is called the "Swabian knot". The deceased's hair was originally gray, and became red due to oxidation in the gloomy peat abyss.
Acidic water, low temperature, lack of oxygen are all necessary conditions for preservation. The internal organs, hair, and skin are so perfectly preserved that they can be used to find out exactly what hairstyle a person wore, what he ate before death, and even what he was wearing 2000-2500 years ago.
At the moment, about 2000 people of the swamp are known. Of these, the most famous are the Tollund Man, the Elling Woman, the Ida Girl, the Bog Body from Windeby, and the Lindow Man.
Most bog people, according to radiocarbon analysis, are 2000-2500 years old, but there are also much older finds.
So, a woman from Kölbjerg, died about 10,000 years ago in the era of the archaeological culture of Maglemose.
On some bodies, clothing or its fragments have been preserved, which made it possible to supplement the data on the historical costume of those years. The best-preserved items are: a man's pointed leather cap from Tollund; a woolen dress found near the burial place of a woman from Huldremos; woolen wraps from severed legs from a swamp in Denmark.
In addition, thanks to the finds, on the heads of which hair was preserved, it was possible to reconstruct the hairstyles of the ancients. For example, a man from Klonikawan styled his hair with a mixture of resin and vegetable oil, and the hair on the skull of a man from Osterby was laid over the right temple and tied with the so-called "Swabian knot", which confirmed the Suevi hairstyles described by Tacitus.
The marsh body from Windeby (German: Moorleiche von Windeby) is the name given to the well-preserved body of a teenager found in a peat bog in northern Germany.
The body was found in 1952 by workers employed in peat mines near the village of Windeby in Schleswig-Holstein. Scientists were notified of the find, who removed the corpse from the bog and began research.
With the help of spore-pollen analysis, it was found that the teenager died in the Iron Age at the age of 14. In 2002, using radiocarbon analysis, the time of his death was more accurately dated - between 41 and 118 AD. e. Radiographs showed the presence of defects in the shin bones (Harris lines), which indicates exhaustion and, as a result, growth disorders. Accordingly, death could come from hunger.