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Largest Oil Spill Yet

A person changing the oil on his/her truck
Above: Person changing their truck's oil. Credit: NASA

Quick quiz: what leaks more oil into the world's oceans each year - big oil tanker spills or individual vehicle owners changing their own engine oil? If you said big tanker spill, think again. Nearly nine times the amount of oil spilled from tankers and other transport vessels gets leaked into Earth's seas by do-it-yourself oil changes and other oil use.

About half of all oil that enters Earth's oceans comes from human activity - from mining, transporting, and using petroleum products. Overwhelmingly, the largest runoff of human-generated (anthropogenic) oil into oceans comes from the consumption of petroleum. Nearly 70 percent of global oil release from human sources and 85 percent of North American release arises from oil use, such as from car engines. That's about 140 million gallons of oil worldwide each year. Only about nine percent of human-related release results from transportation activities, including tanker spills.

Mississippi River Outlet Left Image: Terra satellite image of Mississippi River Sediment Plume. The Mississippi River drains more than 40 percent of the continental United States, carrying excess nutrients into the Gulf of Mexico. Decay of the resulting algal blooms consumes oxygen, kills shellfish and displaces fish in a 4,000 square mile bottom area off the coast of Louisiana and Texas, called the "dead zone." More information. Credit: NASA

The EPA estimated in 1989 that half of U.S. car owners change their own oil, but only a third of these properly dispose of the used oil. At an average of 5 quarts per change, that quickly adds up, as the National Research Council estimates that even five quarts can contaminate millions of gallons of water.

Natural seepage from the rocks beneath the sea floor accounts for the other half of oil entry into oceans, that which doesn't result from human activity. Natural seepage occurs over widespread areas of the sea floor, but oil from human sources concentrates at mouths of rivers where they empty into the ocean, threatening sensitive coastal areas. The anthropogenic oil doesn't originate at a single area, but rather washes from roads, parking lots, and driveways into storm and waste sewers and rivers that feed our oceans.

Oiled crow Right Image: Oiled crow in the hands of a rescue worker. Photo courtesy Exxon Valdez Oil Spill Trustee Council.

Over time, animals and plants adapted to the slow natural seepage, but the human activity-related drainage remains a problem. Every year, oily road runoff from a city of 5 million could contain as much oil as one large tanker spill. Two-stroke engines, found in pleasure boats, jet skis, and chainsaws, also provide a large source of oil pollution: each cycle of the engine leaks a little oil out of the combustion chamber. Exhaust from all types of engines contains particles of oil that settle and eventually find its way into the waterways.

Satellite image showing growth (green) in the ocean

Left: Satellite image of the oceans, showing ocean color. Green represents plankton growth. Click image to see movie. Credit: NASA/Orbimage

NASA satellite instruments such as the Sea-viewing Wide Field-of-View Sensor (SeaWiFS) on the Orbview-2 spacecraft, the Moderate resolution Imaging Spectroradiometer on the Terra and Aqua satellites, the Topex/Poseidon mission study the oceans from space. Their combined observations help monitor the health of the Earth's seas and establish baseline data against which scientists can compare new observations.

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Oil Pollution
Katie Stofer
NASA Goddard Space Flight Center