Slush, also called slush ice, is a slurry mixture of small ice crystals (e.g., snow) and liquid water. In the natural environment, slush forms when ice or snow melts. This often mixes with dirt and other materials, resulting in a gray or muddy brown color. Often, solid ice or snow will block the drainage of fluid water from slushy areas, so slush often goes through multiple freeze/thaw cycles before completely disappearing. In areas where road salt is used to clear roadways, slush forms at lower temperatures than it would ordinarily, and only in salted areas; this can produce a number of different consistencies over the same geographical area.