How a dormant volcano and ancient lava tunnels shaped South Korea's largest island

Countries & Cities · Published 29 September 2026 Swipe more like this →

In short: Jeju Island is a volcanic masterpiece, home to the world's most impressive lava tube network and South Korea's tallest peak. Designated a UNESCO World Heritage site in 2007, this island offers a rare look at global volcanism, featuring unique ecosystems and archaeological treasures that date back to the Paleolithic era.

Located 130 kilometers off the southern coast of the Korean Peninsula, Jeju is a volcanic island spanning 1,846 square kilometers. At its heart lies Hallasan, a dormant volcano reaching 1,950 meters above sea level. This central peak is surrounded by 360 satellite volcanoes, reflecting a long history of geological activity that began in the Cretaceous period and continued through the early Tertiary. While the most recent eruptions occurred roughly 5,000 years ago, classifying the volcano as active remains a subject of debate among experts who argue that further monitoring is essential for a definitive status.

The island's UNESCO recognition is largely due to the Geomunoreum Lava Tube System, widely considered the finest of its kind globally. These subterranean passages are celebrated for their visually striking mineral formations and stalactites. Beyond its geology, the island serves as a biological sanctuary. Since separating from the mainland 10,000 years ago, Jeju has developed a distinct ecosystem, including 33 plant species found nowhere else. The Mt. Halla National Park, protected as a nature reserve since 1966, showcases a rare vertical distribution of flora across subtropic, temperate, and frigid zones.

The island's history is as deep as its caves. Archaeological findings within the Pillemot Cave indicate that humans have inhabited Jeju since the Paleolithic period. Today, the reserve supports a diverse array of wildlife, including endangered mammals and various bird species. The surrounding waters, once a vital corridor for large whales like the blue and humpback, continue to host marine life such as Indo-Pacific bottlenose dolphins. This combination of geological, biological, and historical significance makes Jeju a unique window into the natural and human past.

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