Hawaii’s Kilauea volcano is famously effusive: Low-viscosity lava has been oozing out of the main caldera and two active rift zones along the southern shore of the Big Island since 1983. But scientists suspect that Kilauea’s eruptions haven’t always been so mild. In the past 2,500 years, at least two cycles of explosive eruptions lasting several centuries each have rocked the island. The switch from effusive to explosive is likely to occur again, scientists say, but probably not anytime soon.