Iozan is one of the active volcanoes in Akan Manshu National Park. There are more than 1,500 fumarole (an opening in a planet's crust which emits steam and gases) that rumble, causing steam which contains sulfur particles to spout into the air. In the observation space of Iozan, it is possible to get up close to see the appearance of the steam and sulfur.

About Iozan (硫黄山)

Iozan is an active volcano which formed about 7000 years ago. On the slope of the mountain with an altitude of 512 m, there are over 1,500 fumaroles in various sizes, and volcanic gas containing sulfur gush out from below. The fumarolic zone is characterized by yellow crystals with hardened sulfur content. Furthermore, the risk of eruption at Iozan is the lowest (Level 1, last checked on February 2019), you can have fun sightseeing without worry.

Meaning of the name Iozan

The name of the mountain Iozan is derived from 'mountain with sulfur', the official name is Atosanupuri. Atosanupuri means "naked mountain" according to the Ainu people living in this area a long time ago.

Highlights of Iozan

Iozan has two interesting sights you have to see. One is the earth tremor followed by vigorous sulfur steam that rise with a strong force. It’s as if you can see the Earth breathing. There, fairy-tale like yellow sulfur crystals are formed around the spout. The other sight is a field of Azalea, a group of white flowers known as Ezoitsutsuji (エゾイソツツジ) spreading on the foot of the mountain north of Iozan. These white flowers bloom all at once in mid-June till early July to welcome visitors.

Precautions for sightseeing on Iozan

There is a smell of sulfur around Iozan, and sometimes visitors may feel sick while sightseeing. Even after leaving the site, the smell may remain on your clothes. In addition, there are no prepared mountain trail on Iozan from the foot to the observation space. It is easy to walk here normally. You can walk here without a problem in sneakers if it isn’t a snow season. Plus, while you’re on the way to the observation space, you might encounter small spouts of hot water gushing near your feet. However, since the water is very acidic and extremely hot, don’t try to touch it.

Iozan Resthouse

A rest house on a plot of Iozan parking lot. They sell souvenirs, a food and drink corner, and there is a toilet here. For tourists visiting Iozan, it is a good idea to try their specialty hot spring eggs and soft serve ice cream here. Souvenirs such as sweet mini candies that appear like lumps of sulfur are also popular.

Spot information

  • Spot name: Iozan Rest House
  • Business Hours: 8:00am to 5:30pm (Open everyday)
  • Payment: Credit Card (JCB, AMEX)

Access to Iozan

The closest station is Kawayu Onsen station on the JR Senmo Main Line if you go on foot. It takes about 20 minutes to travel from Kawayu Onsen station to Iozan. In addition, there is a Kussharo Bus which goes round the Akan Mashu National Park. If you ride this bus, you can travel from Kawayu Onsen station to Iozan in 5 minutes. However, the round-trip bus service is limited to a certain period, early July to early October, early February to late March.

Spot information

  • Spot name: Akan Mashu National Park Iozan
  • Street address: Teshikaga, Kawakami District, Hokkaido 088-3200
  • Access: 20 minutes walk from Kawayu Onsen station, 5 minutes by Kussharo bus from Kawayu Onsen station