Indonesia’s Mount Merapi erupted on Monday, pouring ash and lava into the sky on Java, a densely populated island that is home to more than a dozen active volcanoes. There was no immediate report of evacuations and nobody was killed, though hot ash from the eruption covered several villages and nearby towns. Mount Merapi, the most volatile of more than 120 active volcanoes in Indonesia, has seen an increase in activity in recent weeks. Sunday morning, the lava dome partially collapsed when a series of eruptions began, with the initial blast sending hot ash 3,280 feet (1,000 meters) into the atmosphere, said Hanik Humaida, the head of Yogyakarta’s Volcanology and Geological Hazard Mitigation Center. The mountain spewed at least three new pyroclastic flows—avalanches of rock, ash, and volcanic gas—on Monday, she added, adding that it’s common for eruptions to last several days. Indonesia has more active volcanoes than any country and …