WASHINGTON—Explaining that the undertaking could take up to 20 years, members of the National Oceanic and Atmospheric Administration announced a major initiative Friday to begin mapping the massive layer of garbage on the ocean floor. “With roughly 110 million square miles of oceanic trash remaining completely unexplored, we hope that next year we can start producing bathymetric maps of the rugged detritus ranges and vast refuse flats at the bottom of the Pacific Ocean,” said NOAA administrator Jane Lubchenco, who explained that topographers will use multibeam echosounders to create a digital terrain model displaying the many trash formations suspected to exist on the seafloor, including deep trenches in tire piles, countless scrap metal ridges, and detergent bottle shelves. “It may be ambitious, but we hope to eventually define the contours of every square inch of the plastic and metal debris at the bottom of the world’s oceans. Unfortunately, almost all of the data we currently have is limited to the junk features within five miles of our coastlines—frankly, we know more about the garbage in our solar system than our own deep-sea litter.” Lubchenco added that the maps could be extremely beneficial to marine biologists hoping to study the sea life that have evolved to live in and around the waste bed.