Schlichting!: Ice pillars from the ground
On the surface of moist soil, water emerging from the capillaries sometimes freezes into thin ice needles. These cluster together in bundles and grow upward in a columnar shape like a snow comb.
© E. Joachim Schlichting (detail)
Hills Ice Pillars: Thin strands of ice rise from partly sandy, clayey soil on a wet slope.
After the air temperature dropped just below freezing one winter’s day, I set out in search of hair snow. In fact, such conditions are considered favorable for this: cold air above the soil where the temperature is just above zero degrees Celsius. However, my search was unsuccessful. Apparently, other conditions for the appearance of this most delicate of all types of ice were not met as well compared to previous years.
However, my disappointment quickly vanished when, on my way back up the barely-vegetated mountain slope, some strange-looking snowflakes flashed in my face. They looked as if they had been squeezed out of the base with a piping bag used for frosting cakes. However, in many cases, the cross-section of the snowflakes exactly matched the shape of the holes from which they emerged. Some structures carried the missing piece of flooring on their end like a hat. In some cases, adjacent strands worked together to lift a small block of earth out of the ground.
The soil in which the ridge ice was discovered was partly sandy and partly clayey. Except for the thin, frozen surface crust, the surface was relatively smooth thanks to its moisture, and even gave way under my body weight in certain places.
If you look closely at the cones, you can see that they are made up of a bunch of ice needles frozen together. Hence its English name “Needle Ice”. On the other hand, the German term Kammeis refers to the similarly aligned structure of an entire system of cones. The maximum length I have found for specimens is about 15 cm. Under particularly favorable conditions, they can grow twice as much.
© E. Joachim Schlichting (detail)
The soil carried | The columns sometimes take with them parts of the soil from which they grow.
Hills ice is formed mainly by water penetrating the surface from the pores of moist, sandy and porous soil. It usually evaporates there. The fluid flow is driven by capillary forces, which rely on a fundamental physical connection: less interfacial energy is needed to form an interface between hydrophilic sand than between sand and air. Since as much energy as possible is always released into the environment under appropriate conditions (second law of thermodynamics), air is always replaced by water and thus displaced from the pores.
There is amazing physics hidden behind many everyday objects. Feel it for many years Hans Joachim Schlichting He explains these phenomena in his column for readers of “Spectrum of Sciences.” Schlichting is a professor of educational physics and worked at the University of Münster until his retirement.
When the air temperature drops below zero degrees Celsius, the water freezes at the exit holes. Then, driven by the flow of water, the ice needles grow away from the ground. This process is supported by the fact that frozen water expands. The resulting liquid freezes when it enters the cold zone. Therefore, contact between the water-filled capillaries and the ice needles is always maintained.
Strongly favorable combination
In the transition zone between the ground and cold air, adjacent needles usually freeze together in bundles and form a rather thick columnar structure – comb ice. Interfacial energy is again crucial for this purpose. Because there is much less heat between water and ice than between air and ice, this process is also largely driven by the release of energy into the environment. Such mergers also occur when fresh ice cubes come into contact with each other.
Ice Ridge is not seen often. Obviously, external conditions such as soil moisture, air temperature or humidity must match. Even when these requirements are met, ridge ice columns are often twisted, twisted, and sometimes form strange structures. The heterogeneity and instability of the permafrost layer are responsible for this. On the one hand, it must be strong enough to hold the cones, but on the other hand, it must be flexible enough to allow growth movements across the frost layer.
Even immediately adjacent ice needles experience slightly different conditions and grow at different speeds or in slightly different directions. Due to the rigid connections in the column structure, corresponding bends occur. The tendency is always towards the side of the slower growing needles. Sometimes there is little resemblance to the straight teeth of the comb of the same name.
© E. Joachim Schlichting (detail)
Chaos on the floor Many ice needles emerge from the ground and grow in different directions.
On the day the ice ridge was discovered, the ice began to melt as the air temperature rose. This caused the screws to disappear, causing them to topple in rows, eventually leaving an icy field of rubble behind. This demonstrated the precise correlation between the strength of the permafrost layer and its susceptibility to deformation. The ratio is responsible for the limited length of the tongue, especially on slopes. Because of gravity, they simply fall when they reach a critical height.
“Design and Transformation / Eternal Entertainment for the Eternal Mind”Johann Wolfgang von Goethe
Because ridge ice columns often lift portions of the ground, a little soil is moved down the slope each time. In the long term, this phenomenon could contribute to the settlement of the landscape.
Nature has created two other forms of ice pillars that are similar in appearance, and each strives upward under specific conditions. These include the hair icicles mentioned at the beginning and the icicles that sometimes form on water-filled vessels that freeze. Aside from the fact that they are all made of frozen water, they rely on completely different mechanisms.
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