uudelleenjäätymistä

Uudelleenjäätymistä is a Finnish term that translates to "refreezing" or "regelation" in English. It refers to the phenomenon where ice melts under pressure and then refreezes when the pressure is removed. This process is particularly noticeable when a heavy object is placed on ice.

The scientific explanation for uudelleenjäätymistä lies in the unique properties of water. Unlike most substances, water expands when it freezes. This means that ice is less dense than liquid water. Consequently, the melting point of ice decreases as pressure increases. When pressure is applied to ice, such as by the weight of an object, its melting point drops below 0 degrees Celsius. This allows the ice to melt even at temperatures that would normally keep it frozen.

Once the pressure is released, the water, now at a temperature below its normal freezing point due to the previous pressure, quickly refreezes. This is because the water molecules are still in a state where they can easily form ice crystals again. The refrozen layer effectively seals the object to the remaining ice.

A common practical demonstration of uudelleenjäätymistä involves hanging a thin wire over a block of ice with weights attached to each end. Over time, the wire will slowly cut through the ice block. The wire melts the ice under its weight, but as it passes, the water refreezes above the wire, leaving the ice block seemingly intact, although now separated into two pieces. This phenomenon has applications in various fields, including ice sculpture and understanding glacier movement.