Suwolbong tuff ring (a volcanic edifice created by hydrovolcanic explosion which is less than 50 m in height and has slopes that are less than 25 degrees) is one of many tuff rings that were created about 18,000 years ago. Also known as the ‘textbook of volcanology’, the tuff ring was designated as the natural monument of Korea (no. 513) in 2010. In addition, the area is protected under the Public Waters Management Act which was enacted in 1999. The majestic sea cliffs which stretch for few kilometers along the coast have academic as well as landscape value. Suwolbong is a low-relief mount of pyroclastic deposit (a deposit composed of solid fragments ejected by a volcanic eruption) located at the western margin of Jeju Island. The maximum thickness of the deposit is about 70 m. Present topographical contours of the mount together with a sedimentological study suggest that the mount represents the partly preserved rim bed of a tuff ring, whose vent (a circular depression in the ground caused by volcanic activity) lies several 100 m seaward of the present shoreline. The pyroclastic deposit of Suwolbong provides excellent and continuous sea-cliff exposures (a visible exposure of bedrock on the surface). The exposures of the Suwolbong tuff ring are so continuous that individual tuff layers can be correlated bed-by-bed from the proximal to the distal parts of the entire tuff ring deposit. Such an excellent outcrop condition is highly unsual, and there are no other examples like those of Suwolbong outside Jeju Island. As the pyroclastic surge (turbulent, ground-hugging flows of volcanic gases, steam, and pyroclastic materials) becomes diluted downcurrent through fallout of suspended loads (sediment in a flow fluid that is carried in the upper body of the flow) and mixing of ambient air, it becomes turbulent and separated into coarse-grained bedload (sediment in a flow fluid that are transported along the bed) and overlying fine-grained suspension, forming thinly stratified units with diverse bedforms. Further downcurrent, the surge may be either cooled and deflated or pushed up into the air, depending on its temperature. The above model is the first depositional model of pyroclastic surge based on sedimentological study of pyroclastic surge deposits. The model is introduced in a number of geological literatures and textbooks. The Suwolbong tuff ring is thus very famous in the volcanological community and is very suitable for geological field excursions. Geo-trail events have been held at Suwolbong since 2011. The event attracts more than 20,000 tourists.