A Foundation of Fire
The dramatic peaks of Seoraksan National Park are carved from granite plutons, immense bodies of igneous rock that intruded into the region's older Precambrian metamorphic rocks during the Cretaceous period. Zircon U-Pb analysis dates this coarse-grained Seoraksan granite to approximately 88 million years ago. This makes it the youngest major intrusion in the mountain range. The granite is primarily composed of quartz, feldspar, and mica (biotite), a mineral combination that prepares the way for its eventual sculpting. The prominent Ulsanbawi Rock, a monolith of six peaks rising 200 meters from its base, is an example of this Cretaceous granite. Its very existence is due to it having fewer cracks, or joints, than the surrounding rock, which has long since eroded away.
The entire Taebaek mountain range, of which Seoraksan is a part, was shaped by prolonged tectonic uplift. This uplift exposed the deeply buried granite to the surface, initiating the weathering processes that continue to shape the landscape. The park is a composite of different geological eras, with granites from the Proterozoic, Jurassic, and Cretaceous periods all present, each supporting a distinctive style of topography. The most spectacular features, like the sharp-crested ridges, domes and fins, are associated with the younger, more resistant Cretaceous granites.