The nature of the Earth is amazing and diverse. There are many places and phenomena that evoke the most diverse feelings in a person - from delight and reverence for the forces of nature to panic and horror. Today science has studied and explained most of the natural phenomena, however, a person is not able to prevent many of them, and he himself involuntarily provokes the occurrence of some. Quicksand - a phenomenon that has long remained a mystery - is not particularly spectacular and majestic. But people who managed to get out of the sandy captivity remember such an "adventure" with horror.
It should be said right away that the widespread opinion that quicksand can pull a person headlong is an exaggeration. However, they are really dangerous, as it is very difficult to free yourself without assistance. Trapped in the sand, people died from dehydration, sunburn, drowned during high tides, because they did not have time to save them in time.
How quicksand is formed
It is absolutely impossible to simply, by eye, determine that the place in front of you is mortally dangerous. The sun dries out the top layer of sand, sometimes even some vegetation appears on it. One gets the impression that this is the most ordinary sand. As a matter of fact, the way it is - ordinary, only very fine, like dust.
The main reason for the occurrence of the phenomenon is that the properties of dry and wet sand are different and strongly depend on how much water it contains. Dry sand is free-flowing, since the adhesion forces between individual grains of sand are provided only by the unevenness of their surfaces. If the sand is moistened, the adhesion forces will increase many times over. The water covers the grains of sand with a thin film, the forces of the surface tension of which make them stick together. At the same time, a significant part of the space between individual grains of sand remains filled with air.
If the water fills the space between the grains of sand completely, the forces of surface tension cease to act. A fluid and viscous water-sand mixture is formed. As a matter of fact, the unique properties of quicksand - the ability to rapidly "suck" their victims, and then keep them literally in stone captivity - are explained precisely by its high humidity.
Why quicksand "drags on"
The sand becomes quick-moving if there is a rather powerful underground source under it. The stream of water moving upwards, as it were, "whips up" the sandy surface above it. The mutual arrangement of grains of sand becomes unstable, but nevertheless remains. If a person steps on such a surface, the entire structure will collapse under his weight.
The grains of sand move with the body of the failed person. The structure of the sand mass changes. Now the grains of sand are tightly pressed against each other, and the surface tension forces of the water film form a reinforced concrete frame around his legs. Since there is no air between the grains of sand, a rarefied space is formed with any movement. Wet sand, which has a high viscosity, does not have time to fill the cavities formed during the movement, and the force of atmospheric pressure tends to return the shifting body back. It seems that the sand is addictive.
Scientists believe that another reason for the formation of quicksand is static charges, resulting from the friction of sand grains. Since they are all of the same name, the grip between the grains of sand is weakened.
