Amazing images capture oil extraction controversy

Hydraulic fracturing, also known as fracking, is used to extract oil from deep within the earth. However, there are concerns fracking may contaminate groundwater.

Environmental concerns with hydraulic fracturing include the potential contamination of ground water, risks to air quality, the potential migration of gases and hydraulic fracturing chemicals to the surface, the potential mishandling of waste, and the health effects of these, like cancer.

Many cases of suspected groundwater contamination have been documented. Let's take a look at the environmental concerns.

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A gas flare burns at a fracking site in rural Bradford County, Pennsylvania.

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Signs protesting the process of hydraulic fracturing, also known as fracking, are seen near the town of Calicoon Center, New York.

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Carol French of the Pennsylvania Landowner Group for the Awareness and Solutions holds a jar of cloudy water from her well in rural Bradford County, Pennsylvania.

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People protest against hydraulic fracturing outside the Tribeca Performing Arts Center, Borough of Manhattan Community College in New York.

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Anti-fracking protestors demonstrate at the state legislature in Albany, New York.

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Signs protesting against hydraulic fracturing are seen outside the Tribeca Performing Arts Center, Borough of Manhattan Community College in New York.

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Abram Loeb, centre, celebrates with other protesters after collectively reading a statement against hydraulic fracturing at the Tribeca Performing Arts Center, Borough of Manhattan Community College in New York.

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Alex Knapp, left, and his father Albert Knapp of Berkshire, hold placards as they protest in favour of the drilling process of hydraulic fracturing to extract natural gas at the Capitol in Albany, New York.

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A natural gas well is drilled near Canton, in Bradford County, Pennsylvania.

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Chuck Compton, a conductor at Wellsboro and Corning Railroad in Wellsboro, Pennsylvania, couples railcars filled with sand to be transloaded for energy companies drilling natural gas wells in the area.

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Chief Operating Officer of Wellsboro and Corning Railroad Bill Myles shows a sample of the high grade sand his company transloads from railcars for energy companies drilling natural gas wells, in Wellsboro, Pennysylvania.

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Mechanic Mike Huser works on a CAT 3512 engine used to power hydraulic fracturing pumps at Holt Caterpillar, the largest Caterpillar dealer in the United States in San Antonio, Texas.

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A natural gas pipeline is seen under construction near East Smithfield in Bradford County, Pennsylvania.

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Chief Operating Officer of Wellsboro and Corning Railroad Bill Myles examines the end of a 75-car train carrying sand that his company transloads for energy companies drilling natural gas wells in Wellsboro, Pennsylvania.

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Protesters against the drilling process of hydraulic fracturing for extracting natural gas take part in a demonstration at the Capitol in Albany, New York.

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Ron and Jean Carter hold a bottle of their well water outside their home in Dimock, Pennsylvania.

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Craig Sautners places an anti-fracking sign outside his house in Dimock, Pennsylvania.

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Jeff Locker, a Wyoming farmer, displays water filters from his well.

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A worker at EnCana's Frenchie Draw gas-drilling rig in central Wyoming guides sections of steel pipe into an 11,000-foot well.

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A natural gas well is drilled in a rural field near Canton in Bradford County, Pennsylvania.

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Anti-fracking protestors demonstrate at the state legislature in Albany, New York.

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A gas flare burns at a fracking site in rural Bradford County, Pennsylvania.