Jeju uprising to Jeju from Busan and deploying police companies, each 1,700 strong, from the southern provinces of the mainland. The guerrillas retreated to their bases in the forests and caves around Hallasan, an extinct volcano and the highest mountain in South Korea. On April 29, the Korean, non-military, governor of Jeju province abandoned his post, defected, and joined the guerrillas. This caused many police officers, disillusioned by the atrocities they were ordered to commit against their own, to do the same. In response, U.S. military provincial governor William F. Dean ordered a purge of SKLP sympathizers from the ranks of the
Jeju Volcanic Island and Lava Tubes lasted until the early Tertiary period. The most recent eruptions are estimated to be about 5,000 years ago, which puts the volcano into the active classification, meaning eruptions in the last 10,000 years. The designation as active is not agreed by all, as more monitoring and study are needed to better understand the volcano. The island is covered in volcanic rock and volcanic soil produced by Hallasan (Hangul: 한라산). Baengnokdam (Hangul: 백록담), the crater, and lake in it are located at the peak of Hallasan, which was formed over 25,000 years ago. Jeju is scientifically valuable for its extensive system