According to a paper in Physical Review Letters this month, scientists may be able to determine historical precipitation rates by using the rings that form on stalactites.
Stalactites form when water dripping from cave ceilings leave behind minerals. Over time, they grow into spectacular and delicate cave formations.
The surfaces of some stalactites have ridges or rings around them. These ridges are formed by minerals depositing on the upward side, causing the ridges to migrate upward over the years. The migration rate depends only on the flow of water over the surface of the stalactite.
Since the water dripping from cave ceilings depends on the amount of rain above the cave, the ridges can be used to calculate historical rainfall averages.
Stalactites in Silver Cave, Guillin, China via Shutterstock