The Romanian village of Costesti is home to strange rocks called trovants that can balloon 1000 times in size when it rains. Trovants are balls of sand that appeared on Earth following powerful earthquakes six million years ago. They grow when they come into contact with water. Stones as small as .03 inches can swell up to 26 feet across. Scientists believe that beneath their outer shell, the stones have a high mineral content, and when the surface gets wet, the minerals spread and the sand expands. (From Ripley’s Believe It Or Not: Eye-Popping Oddities)
Sylvia Shults, author 