Authorities say about 20 climbers set out Thursday to ascend Mount Dukono on Halmahera Island, ignoring safety restrictions.
It has been thousands of years since the eruption of Mount Vesuvius left the Roman city of Pompeii in ruins, but the ancient archaeological site continues to offer new findings.
Dramatic footage of the eruptions Wednesday shows plumes of gray ash billowing into the sky and streams of glowing lava, accompanied by lightning strikes.
Smoke rings were observed coming out of Sicily's Mount Etna on Sunday, after a vent opened on the southeastern crater last week.
A volcano erupted north of Grindavik, Iceland, just before 8 a.m. on Sunday morning, local officials said.
The new concerns from Iceland's meteorological office come as lava spews for miles across the Reykjanes Peninsula.