Jeju was formed by a series of volcanic eruptions that occurred 100,000 to 1.8 million years ago. About 40,000 years ago, Jeju, the Korean Peninsula, China and Kyushu in Japan were connected by land. During the Paleolithic Period, people migrated to Jeju from the Korean Peninsula and made a living by hunting and gathering food while living under the shade of boulders. They used chipped stone and intricate stone blades as tools for daily life.