column of frost


January 18, 2022

The frost column (Shimobashira) is a column of frozen water that seeps out to the surface of the earth due to capillarity (capillary phenomenon) when the temperature drops below freezing, such as in winter. The frost column is formed by freezing the liquid water in the ground, which is a different phenomenon from the frozen frost caused by the sublimation of water vapor in the air.


The mechanism of frost column generation is as follows. As the temperature drops, the soil containing water on the surface of the earth freezes first. On the other hand, the water in the ground that is not frozen is sucked up by capillarity, but when it reaches the surface of the earth, it is cooled by the cold air and freezes repeatedly, and the frost columns grow. Since the soil is difficult to lift in solidified soil, frost columns are unlikely to occur, and it is likely to occur in plowed field soil. In addition, the Kanto Loam in the Kanto region has a size that allows soil particles to easily form frost columns, so frost columns are likely to form. When a frost column occurs, the soil is lifted and causes various damages called "frost collapse". The roots of the plants float up and the crops are damaged. In order to prevent this, straw is laid on the ground as a heat insulating material to suppress the temperature drop due to radiative cooling and to insulate the temperature from the air temperature so that the temperature on the ground surface approaches the temperature in the ground. On slopes, the soil that has risen due to the frost columns tends to collapse, making it vulnerable to erosion. The number of areas where frost columns are rarely seen is increasing. Generally, it is more common in cold winter years and less in warm winter years. The effects of global warming are possible, but in urban areas and suburbs, the heat island phenomenon also has an effect, and if the roads are paved and the water content is low, frost heaving will not form even if the temperature is low (frost heaving). Due to the temperature difference between the surface and the ground, it occurs only for a shorter period than frost. It is a phenomenon mainly seen in winter, and is a winter season word. In addition, there is a species called Shimobashira (Keiskea japonica) in the Labiatae plant that blooms in autumn. The name comes from the fact that the vascular bundles of dead stems cause capillarity, the frost columns develop from the stems, and their appearance is flower-like and beautiful.


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