Authorities are warning tourists and fishermen to stay more than a mile (two kilometers) from a smoking Indonesian volcano known as "Child of Krakatoa."
The volcano in the Sunda Strait, 80 miles (130 kilometers) west of the capital, Jakarta, was created by the same tectonic forces that led to the 1883 Krakatoa eruption that killed tens of thousands of people.
Its "child," growing five yards (meters) a year, is now 1,320 feet (400 meters) tall and popular among hikers.
Gede Suantika of the Center for Volcanology says the mountain's alert level was raised to the second-highest level last week after the number of volcanic tremors soared from 200 a day to 7,200.
Suantika said Tuesday that he worries a powerful burst could shoot incandescent rocks down its slopes and far into the ocean.