Language Switcher

Unzen hot springs town’s main spot

Unzen hot springs town’s main spot

A World Enclosed in Hot Spring Gas Fumes

The area between Koyu and Shinyu covered in white soil (solfataric soil) is the Unzen Jigoku area. In Buddhist teachings, Jigoku (hell) is where people are punished for evil deeds committed in their past life. With extremely high temperature hot springs and gasses erupting from all around, the strong aroma of sulfur and billowing steam, Unzen Jigoku conjures images of the fearsome Jigoku. A World Enclosed in Hot Spring Gas Fumes.


The identity of the steam at Unzen

It has been thought that the source of Unzen’s energy is the magma reservoir at the bottom of Tachibana bay. The high temperature, high pressure gasses rise through the fissures in the bedrock, and in the process undergo a chemical change, and become extremely hot water. The gasses caused by the boiling hot water come out as violent gasses, and Unzen’s hot springs are made from a combination of those gasses and the groundwater from the surrounding mountains.The identity of the steam at Unzen


Characteristics of the natural hot springs

The driving characteristic of Unzen’s hot springs is the acidic sulfur from which the springs originate. The hot springs can become as hot as 98℃. They are composed of iron ion, aluminum ion, and sulfate ion. The hot springs are also effective against rheumatism, diabetes, and dermatosis. Furthermore, the gasses that erupt in violent sounds can go up to temperatures of 120℃. Mostly composed of steam, the springs are also composed of carbonated gas and hydrogen sulfide gas, which gives off a strong sulfuric smell.


Solfataric soil and Yunohana

The rocks in the Jigoku area have been affected by the heat, acidic water and gas from the hot springs.  They have become white, and have clay-like solfuric soil properties. You can see white to pale yellow Yunohana rocks scattered around the pores spewing steam and gas at Jigoku. These rocks are formed when a chemical reaction between the hydrogen sulfide in the gasses reacts to the iron and aluminum in the soil to become crystallized. A unique characteristics of Yunohana rocks at Unzen Jigoku is that they are not found in the water, but on the ground.


Unzen Jigoku is the town’s main tourist attraction. There are over 30 of these hot springs, such as Daikyokan, Oito, and Kiyoshichi, which all have white steam billowing from the cracks in the earth’s crust. Furthermore, it is also famed for being the stage for Christian martyrdom during the Edo period.


Unzen tourist association -Official website-