<P> The patch is characterized by exceptionally high relative pelagic concentrations of plastic, chemical sludge, and other debris that have been trapped by the currents of the North Pacific Gyre . Its low density (4 particles per cubic meter) prevents detection by satellite imagery, or even by casual boaters or divers in the area . It consists primarily of a small increase in suspended, often microscopic, particles in the upper water column . </P> <P> The great Pacific garbage patch was described in a 1988 paper published by the National Oceanic and Atmospheric Administration (NOAA) of the United States . The description was based on results obtained by several Alaska - based researchers in 1988 that measured neustonic plastic in the North Pacific Ocean . Researchers found relatively high concentrations of marine debris accumulating in regions governed by ocean currents . Extrapolating from findings in the Sea of Japan, the researchers hypothesized that similar conditions would occur in other parts of the Pacific where prevailing currents were favorable to the creation of relatively stable waters . They specifically indicated the North Pacific Gyre . </P> <P> Charles J. Moore, returning home through the North Pacific Gyre after competing in the Transpacific Yacht Race in 1997, claimed to have come upon an enormous stretch of floating debris . Moore alerted the oceanographer Curtis Ebbesmeyer, who subsequently dubbed the region the "Eastern Garbage Patch" (EGP). The area is frequently featured in media reports as an exceptional example of marine pollution . </P> <P> The patch is not easily visible, because it consists of tiny pieces almost invisible to the naked eye . Most of its contents are suspended beneath the surface of the ocean, and the relatively low density of the plastic debris is, according to one scientific study, 5.1 kilograms per square kilometer of ocean area (5.1 kg / km). </P>

When did the great pacific garbage patch start