Hallasan National Park (9.6 km), Seokgulam Trail (1.5 km), Gwaneumsa Trail (8.7 km), Donnaeko Trail (7 km), and Eoseungsaengak Trail (1.3 km). The longest trail is Seongpanak Trail which takes about 4.5 hours. Hallasan comprises 153.112 km of the Jeju Island. It rises 1.950 m above the sea level which means the highest mountain in South Korea. This mountain was formed in the fourth Cenozoic era by outburst of volcano. It is mostly composed of basalts. It is extending east and west, and it has high and gradual descent. On the other hand, the south part of the mountain is steep. In the
Hallasan and study are needed to better understand the volcano. There is a crater lake on Hallasan called Baengnokdam (백록담/), literally "white deer lake." It is formed by the collapse of the top of the ridge by the movement of magma underground. There is a legend attributing the name of the lake to otherworldly men who descend from heaven to play with white deer. Depending on the season, the circumference of the lake is up to 2 kilometers with a depth up to about 100 meters. The configurative rocks of the eastern and western walls of Baengnokdam are different. The eastern