Hallasan

Hallasan is a massive shield volcano located on Jeju Island in South Korea.

It serves as the primary landform for the entire island. In fact, a local saying states that Jeju Island is Hallasan, and Hallasan is Jeju. The mountain is the highest point in South Korea. It is widely considered one of the three most important mountains in the country. The area is protected as Hallasan National Park. It was also designated as South Korean Natural Monument number 182 in 1966.

The volcano formed through a long geological process. It began during the Pliocene epoch on a continental shelf. This shelf sits about 100 meters below sea level. Successive eruptions of basalt and trachyte lava built the island upward. This lava eventually rose above the ocean surface. Today, the mountain reaches a height of 1,947 meters. At the summit, there is a large volcanic crater 500 meters wide. The flanks of the volcano feature about 360 parasitic cones. These smaller volcanic hills are called oreum in the Jeju language. Most are cinder or scoria cones, but some are lava domes. There are also 20 tuff rings near the coast formed by underwater phreatic eruptions.

A notable feature at the summit is the crater lake called Baengnokdam. This name translates to "white deer lake."

The lake formed when the top of the ridge collapsed due to underground magma movement. This makes it a pit crater rather than a lava eruption crater. The eastern wall of the lake is covered in thick basalt lava. The western wall is made of a trachyte lava dome. The lake's circumference can reach 1,700 meters depending on the season. Its depth can reach approximately 100 meters. Local legends say otherworldly men descend from heaven to play with white deer here.

Scientists classify Hallasan as an active volcano. An active volcano is one that has erupted within the last 10,000 years. Historical records from the Goryeosa suggest an eruption occurred in 1007 CE. However, geological evidence suggests the last eruption was at least 2,000 years ago. There is still debate among experts regarding this classification. More monitoring and study are required to fully understand its status. The mountain's topography also significantly impacts local weather. For example, sea breezes and wind vectors create temperature variations across the island. In the mid-mountainous areas, maximum temperatures can be 1 or 2 degrees Celsius higher than coastal areas when winds are weak.

The isolation of Jeju Island has created a unique ecosystem. Because the island was separated from the mainland, species evolved differently. Hallasan features a vertical distribution of life due to its elevation. Plants range from subtropical species at the coast to alpine plants at the summit. The mountain hosts 4,000 species of vascular plants in Korea, and many rare species live here. There are 50 special plant kinds found in the highlands of Hallasan. The fauna is also diverse, though mammal numbers are low due to historical isolation. Known mammals include weasels, badgers, and roe deer. Tigers and boars are now extinct on the island.

Birds and insects also thrive in this varied habitat. There are 160 bird species that use Hallasan as a habitat. Nineteen of these species are protected as natural monuments. Ravens are frequently seen along the hiking trails. The mountain is home to 3,315 insect species and 254 spider species. The spiders tend to concentrate on the north side of the mountain.

While the environment is rich, some species like ticks can cause problems for residents and domestic animals. Conservation efforts are necessary to protect these unique biological communities.

Human history and recreation are closely tied to the mountain. Gwaneumsa is the oldest Buddhist temple on the island. It was originally built during the Goryeo period. The temple was destroyed in 1702 but was rebuilt in 1908. Visitors can explore the mountain via five different hiking trails. The Gwaneumsa Trail and the Seongpanak Trail are the only paths that reach the summit. Other routes, such as the Yeongsil Trail, are shorter. Some sections of these trails have been closed since 1994. These closures help to restore and protect the delicate mountain vegetation.