This article is prepared as training aids for students visiting Mt. Sorak. The basement rocks are composed of Precambrian granitic gneiss and porphyroblastic gneiss found in the vicinity of the highest peaks, and Mesozoic sedimentary rocks covered them with unconformity. Granites covering most of this area intruded these rocks as batholith. From the view point of geology, the general view of Mt. Sorak appears to be resulted from the intrusion of granites and the accompanied differential erosion due to the textural and structural differences of rocks. Especially the sheer cliffs seem to be formed by the erosion along joint planes, and the sequent columnar valley by the joint cross and the litholigic change.

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