Why weren’t there warnings for the Mt. Ontake volcanic eruption?

In a few terrifying moments, hikers on Japan’s Mount Ontake were fleeing for their lives as a sudden explosion of dust and steam soared into the sky.

There were no warnings. No shaking ground. Just terror.

How did this happen in an age with sophisticated volcano monitoring?

John Ewert, the scientist-in-charge at the U.S. Geological Survey’s Cascades Volcano Observatory said that not all eruptions can be predicted by earthquakes, or seismic activity.

Typically, when volcanic eruptions of magma (it is called lava once it exits the volcano) occur, they involve the transport of material from deep below ground, triggering earthquakes.

But Ontake’s eruption wasn’t the movement of magma: it was something called a phreatic explosion, which involves steam.

“Steam blasts are very difficult to foresee,” Ewert said.

These types of explosions — sometimes called hydrothermal explosions — occur when the heat balance changes in a shallow part of a volcano.

In the case of Ontake, it’s likely that a pathway opened up which allowed more heat to get to that shallow level. There, it interacted with the groundwater and then pressurized, breaking whatever was sealing the region, and releasing a steam blast.

“You can think of it like a steam boiler,” Ewert said. “You don’t typically see these coming because it’s a sudden release of pressure.”

The victims include hiking enthusiasts from a major insurance company. Members of a group of nature lovers studying wild plants. A construction manager who snapped about 100 photos — found on his scratched and dented camera — to show his wife what she was missing because she had to work that day.

More than 50 people died when Mount Ontake, a popular hiking destination in central Japan, erupted without warning on Sept. 27 in the country’s deadliest volcanic eruption since World War II.

Together, they paint a typical picture of weekend recreational hikers in Japan. A few children and senior citizens, but mostly middle-aged working people enjoying the first Saturday of the fall foliage season.

Most were between 30 and 59 years old, and lived within a few hours’ drive or train ride from the mountain. Three were children, and only five were 60 or older.

“The best season for the leaves just started, the weather was beautiful, it was the weekend, and it was lunchtime,” said Masahito Ono, a Nagano prefecture tourism official.

Hiking has become one of Japan’s most popular outdoor activities. The core fans are middle-aged climbers with some experience, but there are a growing number of beginners: health-conscious senior citizens and fashionable women who sport a casual “mountain girl” look. The number of hikers in Nagano surged to 730,000 last year, a 30 percent increase from five years ago.

With modest slopes and a ropeway that takes visitors part way up, 3,067-meter (10,062-foot) Mount Ontake is one of the easier climbs in the region, recommended as a day-trip for beginners. Several hundred people are believed to have been on the mountain when it erupted at 11:52 a.m.

Rescuers have found 51 bodies, and at least a dozen other people are still missing. Most of the bodies were found at the summit, with others on a trail a short way down.

At Takahashi’s funeral on Thursday, his family showed a close friend an iPhone with at least six photos from what would be the last few minutes of his life: a cotton candy-like cloud floating next to the mountain in a clear blue sky, a sacred gate to a mountaintop shrine, some of his colleagues making their way up. The last photo, apparently shot by a colleague, shows Takahashi standing next to the “Mount Ontake summit” sign, giving a thumbs-up.

“When I saw the iPhone still worked, I thought it’s like a miracle,” said the friend Hiroyuki, who asked that only his first name be used after he was criticized online for posting some of the photos on Twitter. He has since taken the tweets down.

Takahashi seems happy in the final photo, but he’s not quite smiling. “Maybe he saw signs of the eruption,” Hiroyuki said, adding he has trouble accepting that his best friend died, leaving behind his wife and two children.

Construction company employee Izumi Noguchi, 59, was climbing alone, as his usual hiking companion, his wife, Hiromi, had to work, she told Japanese broadcaster NHK and other TV stations. His compact camera was banged up, but the memory chip inside was undamaged. She printed all 100 shots. The last one is of an enormous plume billowing from the crater behind a mountaintop lodge.

“This is an amazing photo. But I wish he had fled instead of taking pictures. I’d rather have him back,” Hiromi said. “I hope to hike up there someday, perhaps 10 years later. I want to see what my husband saw.”

Source Credits: Global News and

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