Rock Doc

From time to time I give public talks on climate change – those large-scale changes geologists have been studying since the 1830s. At those talks I’m often asked a basic question about climate that, until now, has stumped scientists. Here’s the background.

In the 1830s, a Swiss naturalist named Louis Agassiz started promoting the idea that Europe had once been enveloped in a cold time in which large areas had been covered in glacial ice. He called that interval “the Ice Age.”

Working in this country in later decades, geologists studying glacial debris and soil layers came up with the idea that...