This post concerns the tsunami-driven rafting and associated trans-oceanic transport of shallow-marine animals that took place March 11, 2011 because of the magnitude 9 earthquake along the east side of Japan. The quake was caused by an undersea megathrust (18 km depth) east of the Sendai area, Japan.
Google Earth Image showing the epicenter of the quake and the arrows indicate the main directions of the tsunami-generated waves that transported debris eastward toward North America.
The quake-related earth movements lasted approximately six minutes and created huge tsunami waves less than an hour after the quake. These waves reached 128 feet above sea level and traveled inland as far as six miles (10 km) in the Sendai area, in Honshu of northern Japan. The waves overrode the world’s largest sea walls. If you want to see hundreds of photos and incredible videos of the effects of the quake, just Google: Japan 2011 quake. You need to see a sampling of them in order to begin to comprehend the amount of damage caused by this quake event.
According to the National Ocean Service [see reference below] in March 2016, the earthquake and related wave damages claimed 16,000 lives and injured 6,000 more. At least 50,000 people were forced to evacuate. Although 70 percent of the debris sank nearshore, an estimated 1.5 million tons of debris was sent adrift eastward across the northern Pacific Ocean. Many species and debris were transported up to 4,300 miles from Japan to Midway Atoll, Hawaii, south-central Alaska, as well as to British Columbia, Washington, Oregon, and California.
The quake, which was felt all across northern Japan, also damaged severely the Fukushima Daiichi nuclear power plant (“Number One”) in Okuma on the Pacific coast and released highly hazardous toxic/radioactive wastewater into the sea and also radiation into the air. Even 12 years after this historic meltdown, this power plant remains a highly hazardous toxic waste site. It is located about 100 km (60 miles) south of Sendai.
At least 289 species of living invertebrates were tabulated. Most were invertebrates: sponges, bivalve mollusks (e.g. mussels, oysters), gastropod mollusks (“sea slugs”), worms, cnidarians (e.g., sea anemones), bryozoans, arthropods (e.g., isopods and amphipods, and crustaceans (e.g., gooseneck barnacles and crabs), as well as barnacles and echinoderms (e.g., sea stars). A few (living) fish were also transported. Mollusks were the most abundant taxa.
Note: No four-legged (including rats or primates (i.e., monkeys) were transported by the rafting.
Most of the debris consisted of durable, non-biodegradable (man-made) material such as plastic, fiberglass, and Styrofoam. Small boats (including some “ghost” boats and large pieces (up to 170 tons!) of boat docks (some at least 80 feet long) were also transported. Natural debris, such as woody debris and even large pieces of trees, is short-lived and decomposable—rarely surviving a trip, that can last many months across the whole Pacific Ocean. Only a few Japanese trees made the trip.
The following references were used in compiling the above information:
Carlton, J.T. and eight others. 2017. Tsunami-driven rafting: transoceanic species dispersal and implications for marine biogeography. Science 357 (no. 6358). Pdf available online for free.
National Ocean Service. March 2016. Ocean service.noaa.gov/aa-updates/japan-tsunami-marine-debris-html
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