April 20 is the sixth anniversary of the Deepwater Horizon oil spill in the Gulf of Mexico. Oil and methane spilled from the uncapped wellhead, a mile beneath the surface, for 87 days. Millions of barrels of oil were released into the ocean and 11 rig workers were killed in the incident.

 Oil floats on the surface of the Gulf of Mexico around a work boat at the site of the Deepwater Horizon oil spill in the Gulf of Mexico June 2, 2010. As the desperate effort to contain the gusher proceeded, the slick stretched farther. Tar balls and other oil debris from the giant, fragmented slick reached Alabama's Dauphin Island, parts of Mississippi and were less than 16 km (10 miles) from Florida's northwest Panhandle coast. REUTERS/Sean Gardner
Image: REUTERS/Sean Gardner

While the full long-term environmental impacts of the spill are disputed, this image shows the oil on the surface of the water in the Gulf of Mexico.

To coincide with the sixth anniversary of the spill, here is a snapshot of some of the world’s worst environmental disasters.

Chernobyl

 A wolf crosses a road in a forest in the 30 km (19 miles) exclusion zone around the Chernobyl nuclear reactor near the abandoned village of Dronki, Belarus, April 2, 2016. What happens to the environment when humans disappear? Thirty years after the Chernobyl nuclear disaster, booming populations of wolf, elk and other wildlife in the vast contaminated zone in Belarus and Ukraine provide a clue. On April 26, 1986, a botched test at the nuclear plant in Ukraine, then a Soviet republic, sent clouds of smouldering radioactive material across large swathes of Europe. Over 100,000 people had to abandon the area permanently, leaving native animals the sole occupants of a cross-border
Image: REUTERS/Vasily Fedosenko

An explosion at the Chernobyl nuclear power plant on the 26 April 1986 caused radiation to be leaked over a large area. To this day, an exclusion zone roughly the size of Luxembourg remains in place, but as this photo shows, animal life has returned.

Exxon Valdez

 Members of the clean up crew in Prince William Sound begin work on the daunting task which lies ahead of them, cleaning up the worst oil spill in U.S. history. REUTERS/Mike Blake
Image: REUTERS/Mike Blake

The Exxon Valdez tanker ran aground in Prince William Sound, Alaska in March 1989. Here workers assess the scale of the task ahead of them after an estimated 11 million gallons of oil spilled into the water.

Love Canal

 A danger sign stands amid a permanently fenced-off section of the area formerly known as the Love Canal, in Niagara Falls, New York, July 18, 2003. Twenty five years ago, Love Canal was America's most notorious toxic dump, where leaking poisons from waste dumped by the Hooker Chemical Company (now Occidental Chemical) forced thousands to flee their homes and awoke the nation to the dangers of pollution. The U.S. government eventually declared emergency evacuations of the area in 1978 and 1980, and relocated more than 800 families and reimbursed them for their homes, which were destroyed. Picture taken July 18, 2003. REUTERS/Mike Segar
Image: REUTERS/Mike Segar

Although serene today, the danger sign points to the risk posed by toxic waste dumping in the abandoned settlement of Love Canal, near Niagara Falls. 21,000 tonnes of industrial waste was buried in the 1940s and '50s. It then began to bubble up into backyards and cellars, resulting in the evacuation of the settlement in the 1970s.

Kuwaiti Oil Fires

 Kuwaiti Oil Fires
Image: NASA's Goddard Space Flight Center

In 1991, around 600 oil wells were set alight at the end of the Persian Gulf War. The whole region was engulfed in smoke, soot and ash, as these images from NASA show.

‘Door to Hell’

 The 'Door to Hell', Derweze, Turkmenistan.
Image: Caters News Agency

Soviet scientists drilling for oil in 1971 opened this crater, near the village of Derweze in Turkmenistan. To prevent the poisonous methane gas posing a risk to local residents, scientists attempted to burn it off. However, it’s been burning ever since, earning the crater the nickname, ‘Door to Hell’.

Fukushima

 A view of the destroyed roof of the No.3 reactor building of Tokyo Electric Power Co. (TEPCO)'s tsunami-crippled Fukushima Daiichi nuclear power plant is seen in Fukushima prefecture February 20, 2012. Members of the media were allowed into the plant on Monday ahead of the first year anniversary of the March 11, 2011 tsunami and earthquake for the second time since the disaster, which triggered the world's worst nuclear crisis since Chernobyl. REUTERS/Issei Kato
Image: REUTERS/Issei Kato

The destroyed roof of the No.3 reactor building at the Fukushima Daiichi nuclear power plant. A 2011 earthquake and tsunami crippled the plant, causing a nuclear disaster and releasing radioactive material into the environment.

Bhopal

 A victim of Bhopal gas tragedy attends a demonstration outside a court in the central Indian city of Bhopal June 7, 2010. An Indian court on Monday sentenced seven people to two years each in prison for negligence in failing to prevent one of the world's worst industrial accidents that killed thousands of people in 1984. REUTERS/Raj Patidar
Image: REUTERS/Raj Patidar

An accident in 1984 at a pesticide plant in Bhopal, India, released poisonous methyl isocyanate. Thousands of people died within hours and thousands more were exposed to the gas.

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