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
Sousaki volcano higher areas of the earth crust. So future activities are possible. The last eruption of this volcano was a side eruption which created new land in the Gulf of Megara, where there are major port and refinery facilities. Sousaki volcano Sousaki () is an extinct volcano and modern solfatara field in northeastern Corinthia, Greece, at the northwest end of the Aegean volcanic arc. The volcano was active 4.0 to 2.3 million years ago, during the Pliocene and early Quaternary periods of the Earth's geological history. There is still significant solfataric activity at this location. The volcano erupted dacite lava. The