And the debris, which includes cars, boats, shipping containers and the contents of thousands of houses including dishwashers and refrigerators, will continue to circulate in the Pacific for decades to come endangering shipping and wildlife.
The garbage is caught in the Pacific's circulatory current systems and will cross the ocean every year – ending up off the coast of California.
The French environmental group Robin des Bois says that a large percentage of the 25 million tons of debris created by the magnitude 9 earthquake and the tsunami that it triggered on March 11 has been sucked out to sea.
After being caught in the swirling currents for a number of years, it will congregate into two floating "garbage patches," one in the east and the other in the west of the Pacific.
Most of the vehicles will discharge their oil and fuel, creating numerous spills, while containers from industrial facilities will leak pesticides, chemicals and a wide range of other pollutants, the organisation said.
The waste will move at a speed of between 5 and 10 miles a day, catching the North Pacific Current.
Off the coast of California, debris is expected to circulate either north or south, taking either the Alaskan or North Equatorial currents back to the western reaches of the ocean.
Much is predicted to end up caught in the vortex of the Eastern Garbage Patch, which is estimated to measure between 270,000 square miles and 5.8 million square miles.
"Over time plastic debris eventually fragments into tiny particles creating 'plastic plankton' or 'microplastic,' which is a serious long-term concern, particularly for marine food webs." the organisation said.