Almost 100,000 people have evacuated their homes on the island of Bali after warnings that the Mount Agung volcano could erupt at any time. Bali officials ordered everyone living within a 7 1/2-mile radius of the mountain to leave.

Here & Now's Jeremy Hobson discusses the science behind predicting volcanic eruptions and the biggest threats now facing the Balinese people with Rosaly Lopes (@rosaly_lopes), volcanologist and senior research scientist at NASA's Jet Propulsion Laboratory.