Lake Onami (Onami-ike)

Lake Onami-ike sits in a volcanic crater at 1,412 meters above sea level, making it the highest crater lake in Japan. The lake formed from an eruption roughly 45,000 years ago, predating the more famous peaks of the Kirishima range including Mt. Karakuni and Mt. Takachiho. That ancient blast was powerful enough to blanket the Miyazaki Plains 50 kilometers east with 20 centimeters of pumice and ash. After the eruption, the crater gradually filled with groundwater to form the lake we see today, ringed by terrain built up from lava that piled around the crater's rim over thousands of years.