Jeokjung-Chogye Basin
Key facts
- Country
- South Korea
- Diameter
- 7 km
- Age
- about 50,000 years
- Location
- 35.53° N, 128.27° E
A broad, round basin about 7 km across, ringed by mountains, in Hapcheon County, South Gyeongsang Province. Its flat floor is rice fields and villages.
The Jeokjung-Chogye Basin, in Hapcheon County in the south-east of South Korea, is a round basin about 7 km across ringed by mountains. In 2020 Korean geologists showed that it is an impact crater, the first confirmed on the Korean Peninsula.
What can be seen. The basin has a flat floor of fields and villages, surrounded by a ring of mountains. Its shape had long puzzled geologists, but it was usually explained as the result of erosion or faulting.
Proof of impact. Scientists of the Korea Institute of Geoscience and Mineral Resources drilled into the basin floor. Beneath lake sediments they found a layer of breccia about 140 m thick. Quartz grains in sandstone within the breccia show planar deformation features, produced only by shock, and a shatter cone, a cone-shaped fracture made by a shock wave, was found in shale at about 130 m depth.
Age. Radiocarbon dating of charcoal in the lake sediments above the breccia suggests that the crater formed about 50,000 years ago. Later studies of the sediment fill have suggested it could be considerably older, so the age is still debated.
What it hit. The target was a sequence of Cretaceous sedimentary rocks, mainly sandstones and shales.
Why it matters. The basin's lake sediments hold a long record of past climate in East Asia. The impactor is unknown.
Did you know?
It was the first impact crater confirmed on the Korean Peninsula, in 2020.
A shatter cone was found in a drill core about 130 m below the surface.
Rice fields and villages cover the crater floor.