70-million-year-old volcanic ash compressed into rock tells of explosive eruptions. Each tuff layer is a frozen moment of ancient volcanism, and the sequence reveals eruption frequency.
A Cretaceous catastrophe frozen in stone
The dramatic cliffs and valleys of Juwangsan National Park are pages from a violent geological history book. The rock itself is primarily welded tuff, a type of igneous rock formed from the hot ash of pyroclastic flows during the Late Cretaceous period, about 70 million years ago. This geological activity was part of the formation of the Gyeongsang Basin, a large depression that accumulated up to 9,000 meters of sediment and volcanic material.
The eruptions that created Juwangsan were cataclysmic. Immense quantities of volcanic ash, so hot that the particles fused together upon settling, blanketed the landscape. This process of welding created a dense, hard rock layer. The composition is rhyolitic, meaning it is rich in silica. Over time, multiple eruptions stacked these tuff layers one on top of another, creating a stratified record of ancient volcanism. The entire region is now recognized as the Cheongsong UNESCO Global Geopark, evidence of its significant geological features.
Reading the layers
As the thick sheets of hot ash cooled and contracted, they fractured into geometric patterns, forming the park's signature columnar joints. These vertical, often hexagonal pillars of rock create the sheer cliffs and rugged peaks in the park's landscape. The size and shape of these columns can provide clues about the cooling rate of the pyroclastic flow.
The stratigraphy—the layering of the tuff—allows geologists to reconstruct the volcanic history. Each distinct layer represents a separate eruptive event. By studying the thickness, composition, and texture of these layers, scientists can infer the magnitude and frequency of the eruptions. For example, some studies of similar tuff deposits in Korea suggest they originated from at least three distinct, large explosive eruptions with periods of calm in between.
The main rock formations are composed of dacite and andesite, and are highly resistant to weathering and erosion. This durability is why the waterfalls and steep canyons, like Yongchu Gorge, are so prominent within the park.
💡Fun Facts
The park is named after a legend of a 9th-century Chinese rebel king, Ju Wang, who supposedly took refuge in the mountain's caves.
The park's welded tuff formations are considered among the top three rocky mountain landscapes in Korea.
The high silica content of the volcanic rock here can lead to the formation of a rare and beautiful rock called spherulitic rhyolite, locally known as "Flower Stone," which has unique spherical patterns.
Juwangsan hosts 88 plant species and 924 animal species, including the Eurasian otter, which is a designated Natural Treasure in Korea.
Open daily, but hiking is prohibited at night. Hours can vary by season, so checking the official website is recommended.
Admission
Fees apply for entry to the Cultural Heritage area which includes the main trails and Daejeonsa Temple.
Accessibility
The main trail through Juwanggyegok Valley to the waterfalls is relatively flat and well-maintained, making it accessible for leisurely walks. More strenuous hikes lead to the mountain peaks.