The consequences of the massive earthquake that struck Japan in 2011 may not be over yet, as more volcanic eruptions like one last month that killed 56 people may be ahead, experts say.

That unexpected eruption of 10,062-foot Mount Ontake in central Japan, the country's second tallest active volcano, that rained ash and stones on unsuspecting hikers has renewed concerns about the volcanoes in the region.

It was Japan's deadliest volcanic eruption in almost 90 years.

It is possible the country is facing a future of elevated volcanic activity as a result of the magnitude 9.0 earthquake of March 11, 2011, says Toshitsugu Fujii, a volcanologist at the University of Tokyo.

"The 2011 quake convulsed all of underground Japan quite sharply, and due to that influence Japan's volcanoes may also become much more active," he says.

Japan has 110 active volcanoes, with some on remote islands and some undersea volcanoes; 47 of them are monitored full-time.

However, Fujii noted, the country has a shortage of volcano experts, which means many of the peaks are not under the constant observation that might catch small changes suggesting imminent activity.

That makes attempts to issue predictions about possible eruptions difficult, he says; of the nine major eruptions in the country since 1977, most provided at best a few hours warming.

Of particular concern is the possible impact of a volcanic eruption on one of Japan's nuclear power plants, some of which are close to possible active volcanoes.

A conclusion by Japanese nuclear regulators that two reactors at the Sendai power plant in the country's south are safe for the next few decades has been refuted by Fujii, who chairs a government panel looking at volcanic eruption prediction.

The regulators said a major eruption in the next 3 decades, the usable lifespan of the reactors, has been ruled out.

Fujii disagreed.

An eruption at any of the several volcanoes in the vicinity of the plant could not only affect the reactors but could cause a nationwide disaster, he said.

A pyroclastic flow from one of them, the active volcano Mount Sakurajima, could easily reach the Sendai plant, located just 25 miles away, he noted.

"It is simply impossible to predict an eruption over the next 30 to 40 years," Fujii says. "The level of predictability is extremely limited."

Prime Minister Shinzo Abe is supporting a restart of the Sendai reactors, saying major renovation have made them safe and that nuclear power is a key to the country's economic recovery.

"Scientifically, they're not safe," Fujii says in response. "If they still need to be restarted despite uncertainties and risks that remain, it's for political reasons, not because they're safe, and you should be honest about that."

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