Geology of South Korea

The geology of South Korea is very interesting. It includes rocks that are very old, some from the Archean. These rocks form the deep base of the land, called the crystalline basement, made of metamorphic rock. South Korea is a small country, but its rocks come from many different times, from the Precambrian to the Cenozoic eras. This means the land has changed and grown over billions of years, making it rich in different types of rocks and layers.

Geologic history, stratigraphy, and tectonics

The K'yŏnggi Massif and Yongnam Massif are north and south of the Okch'on-T'aebaeksan Zone. They are made of complex rocks called gneiss and schist from the Precambrian. These rocks are very old, from the Archean to the Proterozoic eras, and form the base of all rocks in South Korea.

The Korean Peninsula has many rocks from the Precambrian, making up 40% of the land. Most of the land formed after the Paleoproterozoic, but some very old rocks from the Archean can still be found in some places.

During the Paleozoic era, rock layers formed two main groups: the Joseon Supergroup and the Pyeongan Supergroup. The Joseon Supergroup formed from the early Cambrian to the Ordovician, mainly in the Pyeongnam Basin and Okcheon Fold Belt. It includes several groups like the Taebaek, Yeongwol, Pyeongchang, Yongtan, and Mungyeong groups.

The Pyeongan Supergroup formed later, from the Carboniferous to the Triassic, also in the Pyeongnam Basin and Okcheon Folded Zone.

In the Mesozoic era, starting with the Triassic, the Sŏngnim tectonic event affected the Okch'on-T'aebaeksan Zone. This caused some faulting and warping of rock layers. The Taebo Orogeny happened in the Jurassic, leading to large granite intrusions that cover much of the country.

The Gyeongsang Basin formed during the Cretaceous and includes the Gyeongsang Supergroup, made up of the Sindong, Hayang, Yucheon groups, and Bulguksa Granite.

Volcanic activity continued into the Cenozoic and stopped about 50 million years ago. In the last 2.5 million years, Jeju and other islands were formed by volcanic eruptions.