What is Frost?
What is frost?” is a great video for kids to find out more about this phenomenon.
Have you ever walked out early in the morning on a stretch of grass that crunches under your shoes? With every step you take you can hear the distinct sound of something crunching and it actually feels like you are crushing something like eggshells. This is because you are breaking tiny frost columns that built up over the night.
In cold weather, the temperature of the ground can often drop to below freezing point. The water on the surface of the ground has cooled enough to turn into ice. Water on the ground freezes, more water from inside the soil is pulled to the surface and freezes as well. This process continues until tiny sheets of ice rise up from the ground. These are known as frost columns or needle ice because of their appearance.
The reason that the water from inside the ground gets sucked up to the surface is known as capillary action. This is the ability of liquids to flow in very tiny spaces, without the help of and often in opposition to, gravity. If you put the end of one piece of paper into a glass of water you will notice that the liquid starts moving up. The paper is able to absorb the liquid because of capillary action. In this way, water trapped in the soil moves to the surface of the earth, to build this needle ice.
FROST IN AGRICULTURE
Since all you need for frost to accumulate is water, columns can grow on pretty much any surface. Any solid surface whose temperature drops below freezing has the ability to freeze water vapour around it. It might be exciting to feel the crunch of frost columns under our feet on a particularly cold day, but it is responsible for a lot of damage to crops and fruit.
Take a bowl and fill it with mud. Pack the mud down gently and lightly pour a glass of water onto it. Make sure that the soil is soaked completely through but not mushy. Put the bowl into the freezer for a few hours. When you remove it, the soil should be frozen. Now pour a thin layer of water over this and pop it back in. Do you get ice columns?
Mini walls of ice
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