What is an oil slick?

Concept

An oil slick is a continuous or patchy layer of oil floating on the surface of a body of water.

Oil spreads laterally because it does not mix readily with water and is generally less dense, so it remains at the surface.

Application

The term therefore describes the thin film produced when oil spreads over seawater, commonly after a spill or discharge.

Contrast

• Boiled oil describes a heating process, not a surface-layer phenomenon.

• Cooled oil describes a thermal condition, not oil spread across water.

• More than one of the above would require at least two listed descriptions to define the same phenomenon.

• None of the above would require every listed description to miss the definition.

Result: an oil slick is a thin film of oil on seawater.