SAPPORO – After several days of huffing and puffing, Mount Usu in southwestern Hokkaido erupted Friday, nearly 22 years after its last series of blasts from 1977 to 1978.
There were no immediate reports of any casualties or damage to property. Some 11,000 residents of the nearby municipalities of Date, Sobetsu and Abuta had been evacuated to public facilities in safer areas as of Thursday afternoon, and 5,000 more people left the area by Friday evening.
A man in his 60s was found to have been trapped in the deserted Lake Toya hot spring resort later in the day, but was soon rescued by Ground Self-Defense Force personnel, police said.
No lava or molten rock was confirmed to have been released after the blast, but there is concern the eruptions could cause mudslides because the mountainside was covered with a thick layer of snow capped by volcanic ash, and heavy rains were forecast to hit the area from Friday night to this morning.
Experts warned that it may only be the beginning of volcanic activity that could extend over a long period and called for continued vigilance. “No past eruptions at Mount Usu ended in such a small-scale blast,” said Yoshio Katsui, a Hokkaido University professor emeritus.
The eruption occurred at 1:10 p.m., opening cracks on the slopes of the 732-meter volcano, located 70 km southwest of Sapporo, and sending up a huge column of thick smoke.
The National Land Agency said it appears to be a phreatic explosion, a blast caused when volcanic gas heated by underground magma destroys the surface of the mountain. Magma is not usually ejected in phreatic eruptions. Experts pointed out, however, that smoke has risen much higher than is typical in a standard phreatic eruption.
Although the National Land Agency initially reported a small-scale pyroclastic flow — a fluid mixture of molten rock and volcanic ash — was moving toward the Pacific Ocean, a Self-Defense Force unit monitoring the situation said no such flow had been confirmed.
Hokkaido University professor Hiromu Okada, examining the scene of the eruption, said there appears to be no immediate fear of any pyroclastic flows.
The Coordinating Committee for the Prediction of Volcanic Eruptions, a government panel of volcano experts, said that although the current eruption may soon calm down, volcanic activity is likely to continue for an extended period.
The committee also said that more blasts could occur on different parts of the mountain, with underground volcanic activity moving upward in the direction of the mountain’s summit. New cracks could also develop in lower parts of the volcano.
Yoshiaki Ida, a University of Tokyo professor and head of the committee, pointed out that seismic activity prior to the eruption resembled a pattern observed before the volcano’s 1910 eruption, when a total of 45 craters were created.
The committee supported professor Okada’s assessment that the possibility of a pyroclastic flow is low, at least for now. Pyroclastic flows can be as hot as several hundreds degrees and can travel at speeds greater than 100 km per hour. Forty-three people were killed by pyroclastic flows from Mount Unzen in a 1991 eruption in Nagasaki Prefecture.
The column of smoke spewed by Mount Usu at one time reached some 3,200 meters and was drifting eastward, according to the Meteorological Agency. Hokkaido Prefectural Police also said some volcanic lapillus were carried to Abuta.
Since a strong southwesterly wind was forecast Friday night, the agency issued a warning of possible damage from volcanic ash in areas near the mountain. Falls of volcanic ash were observed later in the day in Chitose, about 70 km from the mountain.
Authorities said the eruption occurred 2 km northwest of Mount Kita-Byobu, located on a slope of the larger Mount Usu, and less than 5 km from the Lake Toya hot spring resort area. The eruption occurred at an altitude of 200 meters. National Route No. 230 runs only 200 meters from the site.
The eruption occurred in a southerly direction toward the sea, away from the hot spring area to the north. Authorities said five cracks from the blast were initially spotted in an area 200 meters long and 60 meters wide, which later merged into one crater and continued to belch black smoke.
The local meteorological observatory said ash was covering 30 cm to 80 cm of accumulated snow on the mountainside, threatening to release a mudslide.
There was information that a mud flow was moving close to the fishing port of Irie in the town of Abuta. Authorities said a mud flow was not yet confirmed but possible.
Eruptions at Mount Usu, one of the 86 active volcanoes in Japan, have claimed at least 60 lives in seven blasts since the 17th century.
The last series, between August 1977 and October 1978, claimed the lives of at least two people; a third has never been found.
At that time, the volcano spewed ash onto nearby communities and mudflows were triggered by rain.
Records show that a large area covering today’s Date city and the Lake Toya resort, were hit by pyroclastic flows in an 1822 eruption.
As the column of black smoke shot into the sky Friday, emergency sirens rang over the deserted towns. Police in vehicles patrolling the area, using loudspeakers, urged any people who might be lingering to get clear of the mountain as quickly as possible.
The streets in Date were filled with strong odor of sulfur.
About 50 Ground Self-Defense Force trucks arrived in Abuta around 2:15 p.m. to transport evacuees further away from the volcano. Two GSDF helicopters were also mobilized to airlift some of the residents who had taken shelter in the town’s high school. About 3,000 GSDF personnel and 500 vehicles were dispatched to Abuta.
“I heard no sound and felt few tremors (at the time of the eruption),” Masaaki Hatakeyama, a town official from Sobetsu, near the volcano, was quoted as telling NHK television.
“It’s getting a little dark due to the gray volcanic smoke,” he said, looking outside from the town office.
Speaking before an emergency gathering of Cabinet ministers in Tokyo, Prime Minister Keizo Obuchi warned against large-scale damage and called for all-out efforts to ensure the safety of local residents.
The government also created an emergency task force led by National Land Agency chief Masaaki Nakayama later in the afternoon, the first such action since the January 1995 Great Hanshin Earthquake.
An imminent eruption warning was issued Tuesday as seismic tremors intensified at the volcano and several cracks were later found on and around the mountain.
Fairly strong quakes measuring up to a low 5 on the Japanese intensity scale of 7 had been repeatedly recorded in areas at the base of the mountain since Wednesday. Eruptions are often preceded by heightened seismic activity.
Chief Cabinet Secretary Mikio Aoki said the government will consider setting up temporary housing units — like the ones used after the 1995 Hanshin earthquake — to accommodate residents in case their evacuation is prolonged for weeks or more.
Police banned road traffic from using nearby roads, except for emergency vehicles. Hokkaido Railway Co. is suspending train operations between Oshamanbe and Higashi-Muroran stations.
Transport Minister Toshihiro Nikai arrived in the emergency headquarters in the city office of Date aboard a Japan Coast Guard aircraft. Nikai concurrently serves as the director general of the Hokkaido Development Agency.
“We will do our best to (ensure there are) no mistakes in helping evacuees by sharing information with other ministries, agencies and municipalities and putting a priority on personal safety,” Nikai told reporters here.
He also held talks with Hokkaido Gov. Tatsuya Hori and senior officials of municipalities near the volcano.
Ten ships of the Japan Coast Guard, formerly called the Maritime Safety Agency, were on alert off the Pacific coast near the volcano, officials said.
Eight aircraft also remained on standby near the scene, including one that is equipped with a real-time video image transmission system, the officials said.
The Maritime Self-Defense Force has also mobilized four ships off the port of Toyoura, which are capable of carrying a total of 3,000 people, according to MSDF officials.