Argon-argon precision dating. Identifying the formation period. Securing key data to determine the history of volcanic activity in southern Jeju. Creation dates of Beomseom Island, Munseom Island, and Seopseom Island lined up in the sea off Seogwipo, Jeju Island. Provided by Jeju Island It has been confirmed that Beomseom Island, Munseom Island, and Seopseom Island, lined up in a row off the coast of Seogwipo, Jeju, were formed around the same time about 800,000 years ago. In particular, considering that the three islands are arranged almost in a straight line, the southern waters of Jeju Island at the time...