Earth’s geological history is like a book. At the start of this book you have layers of ancient rock from billions of years ago, and these layers grow younger as you turn the “pages.” But unlike your typical book, Earth’s geological chronicle sometimes has entire missing sections covering hundreds of millions to billions of years—and scientists believe they’ve figured out why.

Geologist John Wesley Powell first identified the “Great Unconformity” at the Grand Canyon, explaining how sedimentary rocks from the Cambrian sat right above much older igneous and metamorphic rocks from over a billion years ago. In a paper published today in Nature, researchers demonstrated how mantle convection over hundreds of millions of years may have resulted in this odd geological arrangement we see today.…