For several months in 2009, Redoubt volcano had residents of Southcentral Alaska on edge. Scientists warned that the volcano could erupt at any time in January. But it wasn't until mid March that Redoubt sent a ash plume thousands of feet into the air.
And Seismologist Diana Roman, with the Carnegie Institution, wanted to understand more about the unusual pattern leading up to the eruption. She says usually right before a volcano erupts there is a short period of something called "seismic tremor." But in the case of the Redoubt eruption, it went on for months:
