oilslick

An oil slick, or oilslick, is a thin film of liquid hydrocarbon that forms on the surface of water or land when oil is spilled, discharged, leaked, or seeps from the seabed or infrastructure. The composition varies with crude oil type and weathering, ranging from fresh, viscous pools to weathered, emulsified residues.

After release, oil spreads rapidly because it reduces surface tension and creates a spreading force on the water surface. Wind and currents drive horizontal expansion, while gravity concentrates thicker regions in certain areas. Weathering processes such as evaporation, dispersion, emulsification, and dissolution can change the slick's thickness and composition over time.

Impacts include harm to marine and coastal ecosystems. A coated feather or fur reduces thermal insulation and buoyancy in birds and mammals. Spills can smother benthic communities, contaminate shorelines, and disrupt fisheries and tourism. Sub-lethal effects may persist even after visible slicks disappear.

Response methods aim to contain and remove the oil, minimize spread, and encourage natural breakdown. Techniques include containment booms and skimmers, adsorption with pads, in-situ burning, and the use of chemical dispersants or bioremediation. Effectiveness depends on oil type, thickness, weather, and sea state, and some oils can persist for years in sediments.

Detection and monitoring employ aerial surveillance, satellite remote sensing, and sampling of surface films. International and national regulations address prevention, response planning, and cleanup duties, such as oil-spill response frameworks, environmental impact assessments, and liability rules.