Deep inside the Greenland ice sheet, radar images have revealed strange, plume-like structures distorting the layering deposited over eons. Now, more than a decade after their discovery , scientists think they have figured out what causes these structures, and it's a real hum-dinger. According to modeling, the plumes are a striking match for convection: the roiling upward transport of heat more commonly linked to the fiery, molten rock churning beneath Earth's crust. "Finding that thermal