At Mt. Aso in Kumamoto Prefecture, a pyroclastic flow flowed down 1.6 km from the Nakadake No. 1 crater during the eruption on the 20th of last month, but at that time, 16 climbers were involved in the mountain trail about 1 km from the crater. There was also a risk of getting lost.
For this reason, councils such as local governments have announced "temporary volcano commentary information" that shows the increase in activity even in the state of eruption alert level "2" where access is restricted by 1 km from the crater. In that case, we decided to close the mountain trail within a range of 2 km from the crater.
In the eruption that occurred on Mt. Aso on the 20th of last month, pyroclastic flows flowed down on the north and west sides of Nakadake No. 1 crater, reaching a maximum of 1.6 km from the crater.
According to Aso City, there were 16 climbers on the mountain trail about 1 km away from the crater at that time, but there were no injuries due to the different directions of the pyroclastic flow.
This mountain trail has an eruption alert level of "2" and was constructed in April so that you can enjoy mountain climbing even if access is restricted within 1 km from the crater.
If the level is raised to "3" and the warning range is 2 km, the mountain trail will be regulated, but if the volcanic activity increases while remaining at level 2, the response has not been decided, and this time, the morning of the eruption day. Although it was closed in, climbers had already entered.
For this reason, the Aso Volcano Disaster Prevention Council, which is created by local governments and meteorological observatories, will hold an extraordinary meeting on the 15th to inform that volcanic activity is increasing under eruption alert level 2 "Temporary volcanic commentary information". Was announced, it decided to close the trail to a range of 2 km from the crater.
Mr. Hiroshi Takaki said, "I learned from the fact that I witnessed a climber desperately descending. I would like to accurately convey the latest information to climbers so as not to cause human damage. Also, I would like to convey the latest information to climbers. I want people to submit a mountain climbing notification to protect themselves. "
The lessons learned from the eruption of Mt. Aso may have involved climbers
At the time of the eruption of Mt. Aso last month, there were climbers on a newly constructed mountain trail near the crater 1 km so that they could enjoy climbing even at eruption alert level 2.
Experts said that if the direction of the pyroclastic flow was different, it might have been involved in the damage. Should decide in advance to take measures on the safe side, such as closing the mountain trail. "
Why are there climbers about a kilometer from the crater?
Until now, the mountain trail of Mt. Aso has a place that passes within 1 km from the crater, the eruption alert level has been raised to 2, and if the range of 1 km from the crater is regulated, it is virtually impassable. I did.
However, since volcanic activity is active on a daily basis and the eruption alert level is often raised to 2, the Ministry of the Environment, which manages the mountain trail, said in April this year that it was very close to the outside within a range of 1 km from the crater. Two new mountain trails have been added to the location, the "Suzume Iwakai Route" on the east side and the "Sarayama Ukai Route" on the south side.
While it was possible to climb to the top of the mountain even at level 2, when the eruption occurred, there were climbers just outside the regulations.
Temporary volcano commentary information that appeared before the eruption How will the locals respond?
Before the eruption on the 20th of last month, the eruption alert level was raised from 1 to 2 on the 13th, and on the 18th and 19th, the Japan Meteorological Agency provided "temporary" volcanic commentary information to inform that volcanic activity was further increasing. It was announced.
In response to the announcement of this information, Aso City and the Ministry of the Environment considered closing the mountain climbing route, but it was actually closed in the morning of the day of the eruption, after climbers had already entered.
Expert "Unpredictable volcanic activity Measures on the safe side"
Professor Emeritus Toshitsugu Fujii of the University of Tokyo, who is familiar with volcanic disaster prevention, said, "I think that damage might have occurred if the direction of the pyroclastic flow was even slightly different. Volcano commentary information is decided in advance by the local government so that if the information comes out with a sign indicating that the risk of eruption is increasing, it can be immediately taken on the safe side, such as closing the mountain trail. It needs to be kept. "
"It is currently difficult to predict in advance when and at what scale a volcano will erupt due to issues common to volcanoes nationwide. Recognize the risk of climbing a volcano, and provide information and weather on volcanic activity in advance. I want you to know the information. "