One of our planet’s most appalling eyesores — and significant environmental problems — is the Great Pacific Garbage Patch, a swirling collection of mostly plastic trash and smaller particles of decomposing debris dumped by humans. Now, according to a newly published study in the journal Chaos by University of New South Wales, researchers have developed a computer model to help figure out where all that the trash is coming from.

The results are a bit startling.

“In some cases, you can have a country far away from a garbage patch that’s unexpectedly contributing directly to the patch,” said Gary Froyland, a mathematician at UNSW.

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Trash that originates in Madagascar and Mozambique, two nations that border the Indian Ocean, most likely flows into the south Atlantic Ocean, according the the model. The researchers also may be able to estimate how long it takes trash from Australia, for example, to drift into the northern Pacific.

According to Charles Moore of the Agalita Marine Research Institute, who discovered the patch in 1997 and has been tracking it ever since, the floating equivalent of a landfill now stretches for hundreds of miles in the Pacific between California and Hawaii. But the Great Pacific Garbage Patch isn’t an anomaly. Scientists say there are at least five giant garbage patches floating in the world’s oceans. Each of the floating masses of trash is located in the center of large, circular ocean currents called gyres that suck in and trap floating debris.

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The researchers also have discovered that the borders of the world’s oceans, which generally are delineated by fast-moving currents, aren’t exactly as they traditionally appear on maps. According to the new model, parts of the Pacific and Indian oceans are actually most closely coupled to the south Atlantic, while another sliver of the Indian Ocean really belongs in the south Pacific.