The mantle isn't liquid, but it's less rigid than sinking oceanic crust, Sunyoung Park, an assistant professor who studies Earth's internal structure at the University of Chicago, told Live Science.

Earth's core, which measures about 4,300 miles across, is comprised mostly of iron and some nickel, along with a few other elements. The outer core remains liquid, enveloping the solid inner core.

A small international team of volcanologists has built a more detailed picture of the Campi Flegrei caldera's internal structure using high-resolution seismic imaging and results from rock physics ...