The earthquake and subsequent tsunami that occurred last March in Japan generated approximately 25 million tons of debris, according to the Japanese Ministry of the Environment. While not all of that debris was washed into the Pacific, the potential impact on our ocean's health from tsunami debris is potentially huge.

While oceanographers are monitoring the tsunami debris, there are many questions and misconceptions about it that need to be addressed.

Where's the floating island of trash?

The fact is, there is no floating island of trash. Despite common misconceptions, marine debris fields are not usually dense patches that can be easily spotted and tracked from plans and other monitoring equipment. Rather, they are dispersed over large areas of the ocean -- debris can be miles apart and even at wide-ranging depths.

NOAA and NASA have been tracking this debris field since shortly after the tsunami hit. However, five weeks after the disaster, the debris was so dispersed that it could no longer be tracked by satellite.

In fact, oceanographers estimate that the tsunami debris may be dispersed over an area 2,000 miles long and 1,000 miles wide—that's roughly the size of California. The fact that it is so dispersed makes the tsunami trash particularly hard to track.

In addition, the variety of debris—which includes objects like homes, fishing vessels and small freighters—makes it impossible to know how much debris is still afloat, has sunk or has degraded.

Tsunami debris is a danger to wildlife

The tsunami debris could have significant impacts on wildlife throughout the Pacific.

Debris washing ashore around the Northwest Hawaiian Islands could damage reefs, introduce invasive species and impact the Laysan and black-footed albatross, Hawaiian monk seal, green sea turtle, and other threatened and endangered species.

Derelict fishing gear could threaten seabirds and migratory Pacific species like bluefin tuna, green and leatherback sea turtles, mako and blue sharks, and whales that use North Pacific waters to forage, breed and migrate.

Projecting landfall

While predicting landfall for marine debris is difficult, researchers are working on projections for where and when the tsunami debris could wash ashore.

Drs. Nikolai Maximenko and Jan Hafner of the University of Hawaii International Pacific Research Center are using computer models and at-sea reporting from ships to project the trajectory of the tsunami debris field.

Their models show that debris is likely to wash ashore on Midway Atoll around February or March of 2012. It could then hit western-facing beaches of the main Hawaiian Islands in late 2012 or early 2013. However, the main mass of the debris field is likely to pass north of Hawaii, so it is likely that only a fraction of the total debris will end up on the shores of the main Hawaiian Islands.

Canada and the U.S. West Coast—especially Washington State—could see debris from Japan washing ashore in 2013, while the remaining debris field is subject to ocean current oscillations and could end up in the North Pacific Gyre by 2015 or 2016. Several accounts of tsunami-generated debris washing ashore have recently been reported for the beaches on Washington State's Olympic Peninsula.

It should be noted that these predictions are based solely on models. One oceanographer, Curtis Ebbesmeyer from the University of Washington, predicts a faster trajectory for surface-drifting debris—plastic, fiberglass boat hulls, etc.—as debris moves faster when exposed to wind. For instance, it's wind and not currents that usually drives oil on the surface of the water during an oil spill.

What can I do?

While this is the latest high-profile case of ocean debris, it is just a small part of the overall ocean trash problem. A tsunami's worth of ocean trash is created every year simply by the things we buy, use and throw away. But there are some simple things you can do to help keep trash out of the ocean:

1. Reduce your use of one-time use items like disposable cups, bottles and straws.
2. Pick up litter and properly dispose of your own trash. No matter how far away the ocean may seem, trash can find a way to the sea.
3. Participate or organize a beach, waterway or area cleanup to support trash free seas.
4. Support legislation to address the marine debris problem.

Get more tips at Keep the Coast Clear.

Is the tsunami debris radioactive?

Because tsunami-generated debris washed out to sea before radioactive water was released at the Fukushima nuclear power plant, it is improbable that tsunami-related marine debris is contaminated. This hypothesis was confirmed in early October when the Russian ship STS Pallada found a 20-foot Japanese fishing vessel northwest of Midway Atoll using coordinates informed by Maximenko and Hafner’s model. The boat was tested for radioactivity, and the results came back normal.

Moving forward, macroalgae and crustaceans will be useful for monitoring the presence of radioactive contaminants that would otherwise be difficult to detect.