The Great Serpent Mound in Ohio has long been a source of mystery. Some believe it’s an ancient astronomical marker, aligned with the movements of the sun and moon.

A version of this article appears in print on June 17, 2025, Section D, Page 3 of the New York edition with the headline: Ancient North America Had Extensive Farming.

A study published in the journal Nature Geoscience has revealed a subtle yet significant phenomenon beneath the North American continent; its ancient bedrock is slowly dripping into the Earth’s ...