TOKYO >> Efforts to utilize pumice generated by an underwater volcano near the Ogasawara Islands in March have begun in Okinawa and Kagoshima prefectures, where huge amounts of the volcanic rock washed ashore at fishing ports and beaches, causing tremendous damage.
To turn the disaster into opportunity, the rock has been crafted into artificial reefs and used in lessons at a nature school.
In Uruma, Okinawa, pumice is now being used for fish reefs at the Ikemi fishing port. Remic Maruhachi, a concrete manufacturer in Gifu prefecture, is working with Ryux Inc., a local company that manufactures soil conditioners, for installing the reefs in the ocean.
In November the first product from the joint effort — a reef block weighing about a ton — was removed from its mold. About 70% of the block was made from pumice, according to Remic Maruhachi.
Other companies have also produced pumice fish reefs, and some ports have already installed them.
Meanwhile, a private nature school in Nakagusuku, Okinawa, uses the pumice in its curriculum. At Neco no Wakuwaku Shizen Kyoshitsu, classes allow local children to handle the pumice, and they watch experiments in which the pumice is heated and turned back into magma.
The school also sends pumice specimens to universities and other institutions throughout the country.
“Pumice is not a nuisance. It serves as a habitat for crabs, too,” said Yu Maruya, a school representative. “I hope the pumice will provide an opportunity to learn about geology in Okinawa, where there are no volcanoes.”
Pumice is also used as a soil conditioner in horticulture; its porous structure allows water to easily pass through it.
Yet despite all the efforts to make the best of a bad situation, an overwhelming amount of pumice is still sitting in fishing ports after being recovered from the sea. While the rock has proved to be beneficial, its use is limited because it is fragile and salty.
The underwater eruption produced more pumice than can be utilized. According to the National Institute of Advanced Industrial Science and Technology, the volcano generated more than 100 million cubic meters of pumice.
Okinawa’s government has collected more than 100,000 cubic meters and plans to use most of it to backfill a mine.
The largest amount of pumice in Kagoshima prefecture — 8,300 cubic meters — was recovered on Yoron Island. Some of it was distributed to residents, most of it was buried and about 120 cubic meters remain.
Kagoshima’s government is working with Kagoshima University and other organizations to develop a fish reef that takes advantage of the rock’s light weight. They plan to float pumice on the sea’s surface and use it as a seaweed bed to provide a home for fish.
Pumice drifted to various locations in October and November, so where did it all end up?
The Japan Agency for Marine- Earth Science and Technology used a supercomputer to predict its movement.
The data shows that the rock was widely distributed in waters of the Pacific Ocean, mainly around Okinawa. Some pumice has also been found in the area near the Sea of Japan and around Hokkaido. The overall amount is now decreasing.
“The situation is stable, and it is unlikely to drift anywhere in large quantities in the future,” said senior researcher Toru Miyama. “But it may drift temporarily due to winds and other factors, so we need to be careful when operating vessels.”
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