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Akan, Mashu, KussharoAkan-Mashu National Park

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Tsutsujigahara Nature Walk and Mt. Iwosan Course

Tsutsujigahara Nature Walk and Mt. Iwosan Courseの写真
Type:
hiking
Time Required:
1 h 5 min.
Distance:
2.8 km
Pass through flowering colonies of Ledum Palustre var. diversipilosum (a relative of the rhododendron) to reach the vehement Mt. Iwosan.

Course Outline

Mt. Iwosan gets its Ainu name, Atosanupuri ("Naked mountain"), from the words atosa, meaning "naked," and nupuri, meaning "mountain." Even now, more than 1,500 fumaroles of various sizes vigorously vent steam on Mt. Iwosan and on this course, you will visit the mountain via the lush Tsutsujigahara Nature Trail. As you walk the trail, you can see Mt. Iwosan on your right, the Kussharo Caldera to your left, and if the weather is good, Mt. Sharidake will make an appearance in the distance. Along the way are Haimatsu Deck and Isotsutsuji Terrace where you can enjoy the flowers of not only Ledum Palustre var. diversipilosum, but also the dwarf stone pines from June to July.

Highlights

Kawayu Eco-museum Center
Kawayu Eco-museum Center

Kawayu Eco-museum Center and Kawayu Onsen Footbath

Kawayu Eco-museum Center provides information about the natural environment in the Mashu and Kawayu areas of Akan-Mashu National Park. There are helpful staff on duty, a lounge space where you can relax by the fire, and a café on the second floor, allowing you to take your time and look around. You can also visit the free footbath along the hot spring river about a one minute walk from the Eco-museum Center, where you can soak your legs in Kawayu Onsen’s acidic hydrogen sulfide spring and acidic sulfur spring.

The walking trail flourishing with Ledum Palustre var. diversipilosum
The walking trail flourishing with Ledum Palustre var. diversipilosum

Colonies of Ledum Palustre var. diversipilosum

As you approach Mt. Iwosan, the nature trail passes through a dwarf stone pine zone, a Ledum Palustre var. diversipilosum zone, a broadleaf forest zone, and a conifer zone. Due to the fumarolic and hydrogen sulfide gases emitted by Mt. Iwosan and the strongly acidic soil, the mountain presents an unusual ecosystem. The stark changes in vegetation are easily noticeable, and although the elevation is relatively low at only 150 meters, you can find alpine fauna such as the dwarf stone pines and Ledum Palustre var. diversipilosum (a relative of the rhododendron).

A smoking, active volcano
A smoking, active volcano

Mt. Iwosan (Atosanupuri)

As the name Iwosan (meaning "sulfur mountain") suggests, the distinct smell of sulfur hangs in the air at Mt. Iwosan (elevation 512 meters). Sulfur was once mined on this mountain and it has more than 1,500 fumaroles of various sizes that actively spew out white volcanic gases. At the Mt. Iwosan Rest House in the foothills, make sure you try one of Mt. Iwosan’s famous onsen tamago, or "hot spring eggs," that are cooked with water from the source of Kawayu Onsen. In fact, it is customary to first eat one of these eggs whenever visiting this area! The iwodama, snacks made to look like lumps of sulfur, are very popular, too.

Course Map

Tsutsujigahara Nature Walk and Mt. Iwosan Course

Course Time

Starting Point
1
Kawayu Eco-museum Center
10 min.
0.4 km
2
Entrance to the Nature Trail
20 min.
0.8 km
3
Isotsutsuji Terrace
15 min.
0.7 km
4
Haimatsu Deck
15 min.
0.7 km
5
Mt. Iwosan Rest House
5 min.
0.2 km
6
Mt. Iwosan (Fumarole)
Terminus
*Course time and distance are estimates.