There's a billion-year gap in Earth's geological history. A new study seeks to explain the mystery.

Now imagine opening it and finding that more than a billion years of pages are missing. That mystery is called the Great Unconformity. A ...

Kayakers who approach Michigan’s Pictured Rocks National Lakeshore regularly encounter evidence that its magnificent multicolored cliffs have dropped into Lake Superior over the centuries. “There are ...

Hike north on the Appalachian Trail and the scenery slowly transforms. Rugged, steep ridgelines in Tennessee and Virginia soften into the broad summits and smooth peaks of Pennsylvania and New Jersey.