Miyake Island's Mount Oyama erupted at 3:50 p.m. on Friday -- its second eruption of the day -- sending smoke billowing as high as 1,000 meters above the crater.
Friday's previous eruption occurred at 4:14 a.m. and created a 1,500-meter smoke plume.
The Coordinating Committee for the Prediction of Volcanic Eruptions said the eruptions were triggered by a landslide that followed the collapse of a crater created by an eruption July 8.
The latest eruption forced some nearby residents to flee from falling ash, village officials said. An evacuation order was issued to 86 residents in the Kamitsuki district, they said.
The island lies some 180 km south of Tokyo.
Officials at the Meteorological Agency said that several booms were heard in the space of a minute during the afternoon eruption, with cinders reaching beyond the mountain's outer rim.
Earlier in the day, the 813-meter mountain spewed volcanic ash that covered roads at the foot of the volcano, they said.
A village office decided to close elementary and junior high schools for the day.
The initial eruption occurred shortly after the island's meteorological observatory confirmed there was a column of smoke rising 1,000 meters above the peak of the mountain.
Pale gray ash was being blown in a northeasterly direction and what sounded like thunder was heard coming from the mountain's summit at around 5:24 a.m., observatory officials said.
It was the second time that Mount Oyama had erupted during the past week. The previous eruption occurred July 8.
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