Deepwater Horizon oil spillThe Deepwater Horizon oil spill (also referred to as the BP oil spill, the Gulf of Mexico oil spill, the BP oil disaster, or the Macondo blowout) is an oil spill in the Gulf of Mexico which flowed for three months from the April 20, 2010.

The impact of the spill continues even after the well has been capped. It is the largest accidental marine oil spill in the history of the petroleum industry.The spill stemmed from a sea-floor oil gusher that resulted from the April 20, 2010 explosion of Deepwater Horizon, which drilled on the BP-operated Macondo Prospect. The explosion killed 11 men working on the platform and injured 17 others.On July 15, 2010 the leak was stopped by capping the gushing wellhead,after it had released about 4.9 million barrels (780,000 m3) of crude oil. It was estimated that 53,000 barrels per day (8,400 m³/d) were escaping from the well just before it was capped.It is believed that the daily flow rate diminished over time, starting at about 62,000 barrels per day (9,900 m³/d) and decreasing as the reservoir of hydrocarbons feeding the gusher was gradually depleted.On September 19, 2010 the relief well process was successfully completed, and the federal government declared the well “effectively dead”.

The spill caused extensive damage to marine and wildlife habitats as well as the Gulf’s fishing and tourism industries. In late November 2010, 4,200 square miles (11,000 km²) of the Gulf were re-closed to shrimping after tar balls were found in shrimpers’ nets. The total amount of Louisiana shoreline impacted by oil grew from 287 miles (462 km) in July to 320 miles (510 km) in late November 2010. In January 2011, an oil spill commissioner reported that tar balls continue to wash up, oil sheen trails are seen in the wake of fishing boats, wetlands marsh grass remains fouled and dying, and that crude oil lies offshore in deep water and in fine silts and sands onshore. A research team found oil on the bottom of the seafloor in late February 2011 that did not seem to be degrading. NOAA declared “an unusual mortality event,” ongoing since last February 2011, after a spike in the number of dead dolphins washing up in Louisiana, Mississippi, Alabama and Florida.

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