Stalagmites Reveal Ancient Secrets

Rock formations show historic rainfall patterns in Borneo.

In a recent study published in Science, researchers used stalagmites, the stone formations that grow on cave floors, to peer into the distant past. Stalagmites contain oxygen isotopes in particular ratios that can help trace rainfall as far back as 100,000 years. While similar records from elsewhere showed rainfall patterns associated with distinct types of cooling and abrupt warming events, the rainfall in Borneo matched only certain cooling events. "It's odd and intriguing that we don't see [these events] over Borneo," says lead author Stacy Carolin. Scientists are not yet sure if something in the region is muting the signal of the warming events or if some mechanism is affecting these other sites but not Borneo. The findings may help refine climate models by comparing the real data from stalagmites with theoretical predictions.

This story originally ran in the September-October 2013 issue as "Time Travel."