Vertical striped strata can be found by the lakeside of the Shirakawa Dam. These layers are due to a geological phenomenon called “folds,” which occur when horizontal layers are curved and or bent due to outside pressure to the strata from both sides. Approximately 11 million years ago, when the entire region of Nakatsugawa was covered in water, alternate layers of mud and sand accumulated to create the striped strata. The strata you see today is a result of those layers being pressed and curved to near vertical by the powerful force of the earth over a long period of time.