The area of Mt. Paektu in Korea has many geologically peculiar spots formed by volcanic eruptions.
The volcanic body of Mt. Paektu is a dome-shaped one.
On top of it there is a crater formed by foundering of the mountain body, which was filled with water to form the Lake Chon on Mt. Paketu.
The lake is surrounded by sommas consisting of the Janggun, Hyangdo, Haebal, Paegam and other peaks.
The crater has hornitos.
The rock mass of the Jong Il Peak is a hornito formed by rising lava of high viscosity about 2 million years ago. It is 1,798 metres above the sea level.
The front of the hornito is a sheer cliff 50 metres wide in the upper part and 80 metres wide in the lower part and its southern slope is a cliff around 100 metres high.
The laccolith in Janggun Peak is found in the somma southeast of the crater of the Lake Chon on Mt. Paektu.
The magma rose along the vertical crack to reach the solid top layer. It failed to perforate the layer, but lifted it up before coagulating into a mushroom-shaped laccolith.
The column of the “mushroom” is 5 to 7 metres wide, the “pileus” 500 to 550 metres wide and its height 34 metres at the highest. The section vividly showing the intrusion of magma is of significance in the geological study and education of volcanos.