This story appears in the August 2010 issue of National Geographic magazine ... They built up during ice ages, when the sea level dropped dramatically, leaving the caves dry.

This story appears in the March 2017 issue of National Geographic magazine ... in mapping new parts of the cave and collecting scientific data. Ice crystals populate Full Moon Hall.

The ocean has a 'conveyer belt.' Here's why it's important. An astonishing—and accidental—Ice Age cave discovery An astonishing—and accidental—Ice Age cave discovery Ice Age mammoth’s ...

This story appears in the October 2010 issue of National Geographic magazine ... When he looks at Mammoth Cave, he sees an obvious human habitat, a great shelter during the Ice Age.