Garbage patch
A garbage patch is a gyre of marine debris particles caused by the effects of ocean currents and increasing plastic pollution by human populations. These human-caused collections of plastic and other debris, cause ecosystem and environmental problems that affect marine life, contaminate oceans with toxic chemicals, and contribute to greenhouse gas emissions. Once waterborne, marine debris becomes mobile. Flotsam can be blown by the wind, or follow the flow of ocean currents, often ending up in the middle of oceanic gyres where currents are weakest. Garbage patches grow because of widespread loss of plastic from human trash  collection systems. The United Nations Environmental Program estimated that "for every square mile of ocean" there are about "46,000 pieces of plastic." The 10 largest emitters of oceanic plastic pollution worldwide are, from the most to the least, China, Indonesia, Philippines, Vietnam, Sri Lanka, Thailand, Egypt, Malaysia, Nigeria, and Bangladesh, largely through the rivers Yangtze, Indus, Yellow, Hai, Nile, Ganges, Pearl, Amur, Niger, and the Mekong, and accounting for "90 percent of all the plastic that reaches the world's oceans." Asia was the leading source of mismanaged plastic waste, with China alone accounting for 2.4 million metric tons. The  best known of these is the Great Pacific garbage patch which has the highest density of marine debris and plastic. Other identified patches include the North Atlantic garbage patch between North America and Africa, the South Atlantic garbage patch located between eastern South America and the tip of Africa, the South Pacific garbage patch located west of South America, and the Indian Ocean garbage patch found east of south Africa listed in order of decreasing size. In the Pacific Gyre, specifically 20°N-40°N latitude, large bodies with floating marine debris can be found. Models of wind patterns  and ocean currents indicate that the plastic waste in the northern Pacific is particularly dense where the Subtropical Convergence Zone (STCZ), meets a southwest–northeast line, found north of the Hawaiian archipelago. In the Pacific, there are two mass buildups: the western garbage patch and the eastern garbage patch, the former off the coast of Japan and the latter between Hawaii and California. The two garbage patches are both part of the great Pacific garbage patch, and are connected through a section of plastic debris off the northern coast of the Hawaiian islands. These garbage patches contain of debris. The  waste is not compact, and although most of it is near the surface of the pacific, it can be found up to more than deep in the water. 2017 research reported "the highest density of plastic rubbish anywhere in the world" on remote and uninhabited Henderson Island in South Pacific as a result of the South Pacific Gyre. The beaches contain an estimated 37.7 million items of debris together weighing 17.6 tonnes. In a study transect on North Beach, each day 17 to 268 new items washed up on a 10-metre section. Identified patches. In 2014, there were five  areas across all the oceans where the majority of plastic concentrated. Researchers collected a total of 3070 samples across the world to identify hot spots of surface level plastic pollution. The pattern of distribution closely mirrored models of oceanic currents with the North Pacific Gyre, or Great Pacific Garbage Patch, being the highest density of plastic accumulation. The other four garbage patches include the North Atlantic garbage patch between the North America and Africa, the South Atlantic garbage patch located between eastern South America and the tip of Africa, the South Pacific garbage patch located west of South America, and  the Indian Ocean garbage patch found east of south Africa.