A soup-like expanse of plastic flotsam twice the size of the United States is floating in the Pacific Ocean. An accumulation of plastic rubbish thrown off ships and oil rigs or from the land, it is kept together by underwater currents.

The “Great Pacific Garbage Patch” stretches from about 500 nautical miles off the Californian coast, across the northern Pacific, past Hawaii and almost as far as Japan and was discovered in 1997 by Charles Moore by chance, while sailing his yacht from Los Angeles to Hawaii. The massive patch of rubbish sits in the “North Pacific gyre” – an area where the ocean circulates slowly because of little wind and high-pressure systems.

The patch cannot be spotted in satellite photographs as it lies just below the surface. Charles Moore said of his experience of sailing through it: “Every time I came on deck there was trash floating by. How could we have fouled such a huge area? How could this go on for a week?”

Moore, now an environmental activist, warns that unless consumers reduce their use of disposable plastics, the plastic soup is likely to double in size over the next decade. More than a million seabirds and 100,000 marine mammals die every year as a result of plastic rubbish. The plastic slowly breaks down into tiny pellets which can attract man-made chemicals and are eaten by fish, thus entering the food chain.