Hantangang River Geopark

ongmakri tuff is an area distributed in Yeoncheon-eup, Dongmak-ri, Dongmakgol Amusement Park andthe geological attraction with excellent magnificent scenery terrain due to erosion of the valley.

Source : Yeoncheon Geological Map(1:50,000)

It corresponds to the representative amusement park of Yeoncheon where a number of tourists visit during the summer because the river flowing from the Jijangbong valley erodes the tuff area and creates a variety of terrain scenery such as Dragon Rock, Turtle Rock, Terrapin Rock etc.Dongmakri Tuff is a rock made by the volcanic activity during Late Cretaceous of the Mesozoic and high alpine from Cheorwon to Jijangsan Mountain to Dongmakri is the Cheorwon basin corresponding to volcanic rocks.Cheorwon Basin consists of Mesozoic Cretaceous volcanic rocks such as Andesite, tuff including Sinseo breccia, indicating that volcanic activities were active at that time.

And you can see the phenomenon that particles making up tuff are getting large toward Cheorwon Area, the north and this provides evidence that the volcanic eruption mouth was located near Cheorwon. Dongmakri Tuff is a pyroclastic rock of dark gray or pinkish gray and consists of ash and lapilli and is also composed of tuff where ash is predominant and lapilli tuff where lapilli is predominant.

Lapilli consists of rock fragments of dark red, axinite fragments of dark green and crystalline fragments and welded tuff forming fiamme by lengthened axinite fragments is observed. Felsic microlite composed of volcanic ash, quartz and feldspar group forms the matrix and rock fragments, quartz, feldspar crystalline fragments and axinite fragments are distributed. If volcanic ash, volcanic bombs rose into the air at the time of volcanic eruption and fell to the lava layer flowing on the ground and other lava is piled up repeatedly, welded tuff with fiamme, the welded structure formed pushed by residual heat of lava not fully cooled yet and weight of lava is generated andyou can see that this fiamme was developed also in lapilli tuff of this area.

Microscopic flake photo of Dongmak-ri tuff -3(Quartz crystal, Plagioclase crystal, Fiamme)