What Is Regelation?Regelation is the phenomenon of melting under pressure and then resolidifying once the pressure is released.
Requirements for RegelationRegelation only occurs for materials that expand upon freezing so that the melting point decreases as external pressure increases. For example, for atm of pressure applied, the melting point of (water) ice falls by 0.0072 °C.
Examples of RegelationRegelation occurs in glaciers. The mass of a glacier allows it to exert enough pressure to lower the melting point of the ice at its base, melting the ice and allowing the glacier to slide over the liquid. Under the right conditions, liquid water can flow from the base of a glacier.
Another example of regelation may be seen by looping a fine wire over an ice cube and attaching a heavy weight to the wire. The pressure the wire exerts on the ice will melt it, allowing the wire to pass through the ice. The water refreezes behind the path of the wire so you can pull the wire through the ice, while leaving the ice cube intact. While regelation is occurring, some of the melting may be caused by heating of the wire under tension.