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
Maitland Volcano volcanic activity created a complex edifice of trachyte and trachybasalt that formerly overlain the central part of the basaltic shield. Magmatism at Maitland continued until about 4.6 million years ago when the volcano went extinct. Volcanic activity at Maitland Volcano was consistent with extensional stresses across the northern Canadian Cordillera that began around 10 million years ago as a result of new plate motions between the Pacific and North American plates. This contributed to lithospheric thinning and decompression melting of OIB-like mantle to produce alkaline Neogene magmatism. The time span of 600,000 years for magmatism at Maitland Volcano is relatively