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 can block the drainage of fluid water from slushy areas, so slush often goes through multiple freeze/thaw cycles before completely disappearing.