Walking somewhere in nature, enjoying the charm of flowering plants, listening to birds whistling cheerful songs, you can accidentally be trapped in quicksand. But you should immediately warn that everything is not so scary, as shown in some films of the "horror" genre. Yes, of course, it is better to avoid them, but at the same time, you should not be afraid. There are several consistent rules, the knowledge of which will help to avoid such situations.
What is quicksand anyway? This is a really interesting natural phenomenon, but not a peculiar type of soil. A mixture consisting of fine-grained material, clay and water (in desert places - a mixture of sand and air). It looks solid, but becomes unstable when pressure is applied to its surface. It is formed when water oversaturates such soil. Ordinary, naturally occurring sand (quarry, mountain, sea) consists of densely packed grains that form a rigid mass (approximately 25 to 30 percent of the space between the grains is filled with water or air). Since many sand grains are elongated,their separation, and then the voids will be from 30 to 70 percent of the mass. This mechanism is similar to a house of cards when the space between the cards is significantly larger than the space they occupy. The liquid contributes to the creation of liquefied soil, which is not able to withstand the weight load.
Quicksand can form in standing and flowing waters flowing upwards (as in artesian springs). Water jets directed upward resist gravity and slow down soil particles. Saturated sediments may look quite solid, but a slight mechanical stress on their surface initiates liquefaction. This causes the sand to form into a slurry and lose strength. Cushioned water produces quicksand, liquefied sediments, and a spongy, liquid-like soil texture. Objects entering such an environment sink to a level at which their weight is equal to the weight of the displaced mixture (from soil and water). Liquefaction is a special case of the phenomenon under consideration. So, in the event of an earthquake, the pore pressure in shallow groundwater instantly increases. Wet liquefied soil loses its strength, which leads to the collapse of buildings and other objects located on its surface.
Quicksands form where natural springs exist, in marshy or wet places, near rivers, on beaches, although they are often not so easy to identify. If you suddenly get into them, then they retreat quickly and gently, reacting with an interval of a couple of seconds. They areare a non-Newtonian fluid, that is, at rest they are a solid (gel-like form), but the slightest impact on them causes a sharp decrease in viscosity. In deserts, they are also found, but extremely rarely, where placers of sand appear, for example, on the lee side of dunes. But the decline is limited to a few centimeters, because once the air in the voids between the sand grains is removed (and this happens quickly), they re-compact.
