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An enormous debris field is creeping toward the U.S. in the wake of the massive earthquake and tsunami that shook Japan in 2011, killing nearly 16,000 people and launching 1.5 million tons of floating objects into the sea.

That most concentrated part of the junk field is easily broader than Texas and centered approximately 1,700 miles off the Pacific coast, between California and Hawaii, although the National Oceanic and Atmospheric Administration (NOAA) hasn't published more precise estimates. The agency estimates that the trash overall is scattered across an area in the ocean about three times the size of the continental United States.

The debris ranges from pulverized particles to entire docks that washed over from Japan, to intact boats, motorcycles, soccer balls, traditional Japanese flooring, and even some Japanese sea creatures never seen on the U.S. West Coast. “High windage” items reached the Pacific Northwest as early as winter 2011. Smaller debris is “sailing” here on the tides -- NOAA estimates that the widely scattered detritus may show up intermittently along shorelines for a long period of time, over the next year or more.

In addition to physical junk, a wave of slightly radioactive water released from the broken Japanese Fukushima nuclear reactor is predicted to reach shore in 2014 -- but scientists point out that it is so diluted that it is harmless.

'We’re finding that all kinds of Japanese organisms are growing on the debris.' — John Chapman of the Marine Science Center at Oregon State University

In one of the more dramatic photos of debris, two rooftops and an upside-down boat can be seen floating in the ocean. In another, a giant dock from Japan washed ashore in Oregon.

Even more interesting may be what's living on the dock.

"At first we were only thinking about objects like the floating docks, but now we’re finding that all kinds of Japanese organisms are growing on the debris," John Chapman of the Marine Science Center at Oregon State University told FoxNews.com.

"We've found over 165 non-native species so far," he added. "One type of insect, and almost all the others are marine organisms … we found the European blue mussel, which was introduced to Asia long ago, and then it grew on a lot of these things that are coming across the Pacific ... we’d never seen it here, and we don’t particularly want it here," he said, arguing that it could be "invasive" and displace current marine life.

Many other creatures have been found, too.

"In the debris we found the Northeastern sea star ... as well as a type of brown algae that's used to make miso soup. We’d never seen it here before."

Chapman added that the migrant creatures took scientists completely by surprise.

"We thought, 'the Pacific can’t be crossed by living organisms from Japan' … and we were wrong, very wrong," he said, adding that while a journey across the Pacific typically kills whatever clings to it, there were just so many pieces of debris launched by the tsunami that some were bound to take paths favorable to whatever organisms were on it.

"It wasn’t just the humans that were thrown around, it was these other things on the shore as well," he said.

And he expects to see more creatures, because lot of debris is still out floating in the Pacific, according to the National Oceanic and Atmospheric Administration and to people who have been out to look for it.

"We found an abandoned boat, a tire, and a tatami matt -- that's traditional Japanese flooring made of woven reeds," Stiv Wilson of the 5 Gyres Institute, which monitors plastic pollution out at sea, told FoxNews.com. Gyres was on an expedition to the "North Pacific Garbage Patch," an area with few ocean currents where tons of plastic garbage accumulates, and that's where he found the Japanese debris.

"We found a fishing vessel that was barely above water. It had Japanese characters on it and was made of fiberglass. On the front of the boat we found a rope that was ripped, so the tsunami wave probably hit it and tore it from dock. Then the wave must have hit it against something else, because the stern and the motor were missing."

Gyres said he and his team also brought a Geiger counter with them to measure radiation.

"We didn’t find anything irradiated, we were getting inconsequential readings. I think there's a little fearmongering about it."

The National Oceanic and Atmospheric Administration agrees, and reports on its site: "Radiation experts agree that it is highly unlikely that any tsunami-generated marine debris will hold harmful levels of radiation from the Fukushima nuclear emergency.

Some debris in West Coast has been tested by the states, including items known to be from the tsunami, and no radioactive contamination above normal was found."

That's fortunate, as fisherman report seeing more debris lately.

"We have been seeing more and more," Glen Spain, Northwest regional director of the Pacific Coast Federation of Fishermen's Associations, told FoxNews.com.

"The major hazards of this stuff is that it can carry invasive species, like the pier that washed up. And the bigger stuff can be a navigational hazard."

The next wave of debris will likely hit shores soon, Chapman noted.

"With winter and spring winds -- that’s when it generally shows up. We're going into that season again soon," he said.

The author of the piece can be reached at maxim.lott@foxnews.com or on twitter at @maximlott.