Slush

[1][2] In the natural environment, slush forms when ice or snow melts or during mixed precipitation.

This often mixes with dirt and other pollutants on the surface, 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 being able to completely drain and disappear.

This is the underlying mechanism causing slush avalanches and their unpredictability and thus hidden potential to become a natural hazard without caution.

[3] Slush can also be a problem on an aircraft runway since the effect of excess slush acting on the aircraft's wheels can have a resisting effect during takeoff, making its projection unstable, which can cause an accident such as the Munich air disaster.