Among the cliffs and glades of western Kentucky, a mile-long trail cuts across a patch of prairie. A sandstone arch called Mantle Rock looms in a nearby hollow, where thick carpets of moss soften the ...

"We know from the rocks that erupt in oceanic volcanoes that the mantle has a lot of different 'flavors,'" Lissenberg told Live Science. These "flavors" are varying rock compositions that come ...