The Great Pacific Garbage Patch is a collection of marine debris in the North Pacific Ocean. Marine debris is litter that ends up in oceans, seas, and other large bodies of water.

The Great Pacific Garbage Patch, also known as the Pacific trash vortex, spans waters from the West Coast of North America to Japan. The patch is actually comprised of the Western Garbage Patch, located near Japan, and the Eastern Garbage Patch, located between the U.S. states of Hawaii and California.

These areas of spinning debris are linked together by the North Pacific Subtropical Convergence Zone, located a few hundred kilometers north of Hawaii. This convergence zone is where warm water from the South Pacific meets up with cooler water from the Arctic. The zone acts like a highway that moves debris from one patch to another.

The entire Great Pacific Garbage Patch is bounded by the North Pacific Subtropical Gyre. An ocean gyre is a system of circular ocean currents formed by the Earth’s wind patterns and the forces created by the rotation of the planet. The North Pacific Subtropical Gyre is created by the interaction of the California, North Equatorial, Kuroshiro, and North Pacific currents. These four currents move in a clockwise direction around an area of 20 million square kilometers (7.7 million square miles).

The area in the center of a gyre tends to be very calm and stable. The circular motion of the gyre draws debris into this stable center, where it becomes trapped. A plastic water bottle discarded off the coast of California, for instance, takes the California Current south toward Mexico. There, it may catch the North Equatorial Current, which crosses the vast Pacific. Near the coast of Japan, the bottle may travel north on the powerful Kuroshiro Current. Finally, the bottle travels westward on the North Pacific Current. The gently rolling vortexes of the Eastern and Western Garbage Patches gradually draw in the bottle.

The amount of debris in the Great Pacific Garbage Patch accumulates because much of it is not biodegradable. Many plastics, for instance, do not wear down; they simply break into tinier and tinier pieces.

For many people, the idea of a “garbage patch” conjures up images of an island of trash floating on the ocean. In reality, these patches are almost entirely made up of tiny bits of plastic, called microplastics. Microplastics can’t always be seen by the naked eye. Even satellite imagery doesn’t show a giant patch of garbage. The microplastics of the Great Pacific Garbage Patch can simply make the water look like a cloudy soup. This soup is intermixed with larger items, such as fishing gear and shoes.

The seafloor beneath the Great Pacific Garbage Patch may also be an underwater trash heap. Oceanographers and ecologists recently discovered that about 70% of marine debris actually sinks to the bottom of the ocean.