The temperature at which ice melts depends on pressure. Unlike many other substances, increasing the pressure lowers the melting point of ice. This also means that the lower pressure on the top of a high glacier increases the temperature at which the ice melts.
Salt is used to lower the temperature at which ice melts, which keeps it from refreezing on sidewalks and streets as well as in hand-cranked ice cream makers. The melting point of the ice decreases as more salt is added until the salt stops dissolving. Salt lowers the temperature at which ice melts on a sidewalk down to about 15.8 F (-9 C).Learn more about Earth Science