East Hokkaido · TeshikagaNo.1127★★Open in map →
Mount Io Atosanupuri
— The steaming sulphur ground above Kawayu Onsen
A live volcano you reach from a car park. Grey gravel, yellow sulphur crust and vents loud enough to hear, all of it a short walk from where the road stops.
- FromKawayu-Onsen Station (JR Senmo Line)
- ~5 minJR, then a short drive
- Mount Io Atosanupuri
The sweet spot
Neither a secret nor a climb. Buses stop here, the car park is charged in the green season, and the nearest steam is minutes from the vehicle. What is unusual is how little stands between a visitor and a live vent: one rope line, and your own reading of the wind.
Where it is
102 more notes in Hokkaido · open the map →What to look for — in walking order
- The car park and its shopcounter and toilets at the edge of the bare ground
- The pale gravel flatbright open ground with no shade, minutes to cross
- The fumarole fieldvents crusted with yellow crystal, hot and loud close up
- The scoured slopegrey rock and sulphur staining where nothing takes root
- The Tsutsujigahara trail headstart of the 2.5 km path down to Kawayu Onsen
How to actually get there
- Take the JR Senmo Line to Kawayu-Onsen Station.
- Cover the last stretch by car or taxi; Hokkaido's official guide gives it as about five minutes.
- Or ride Akan Bus's Pirika-go sightseeing coach out of Kushiro, which sets down at the mountain.
- Walk out of the car park onto the gravel toward the nearest steam.
- Kawayu-Onsen Station, then a short drive
- The Senmo Line reaches Kawayu-Onsen, and Hokkaido's official guide gives the last leg as a five-minute drive. Without a car, Akan Bus's Pirika-go sightseeing coach runs daily out of Kushiro from mid-April to late December and sets down here for thirty minutes, which covers the vent field and nothing else on the mountain.
- Back to Kawayu-Onsen, or on to Kushiro
- Trains on this line are infrequent in both directions, so fix the return before you head out to the mountain. The sightseeing coach does not come back this way at all — it carries on round the loop by way of Lake Kussharo and Lake Akan and finishes in Kushiro.
About the place
Atosanupuri stands near the middle of the Kussharo caldera, a lava dome 508 metres high. Its Ainu name means the bare mountain, and the slope earns it: volcanic gas keeps plants off the ground, so the face stays grey rock and yellow crust. The car park sits on that same ground, and a flat of gravel runs out from it toward the vents. The Japan Meteorological Agency keeps the volcano under continuous watch. The heat that drives the steam also feeds Kawayu Onsen below, where the spring layer runs so close to the surface that the town is named for a river of hot water.
How to enjoy it
Wind decides this visit. Steam drifting away leaves the vents sharp and worth photographing; steam coming at you is sulphur dioxide, and the right response is to move sideways rather than to stand and wait. The car park keeps daytime hours, so an arrival at first light finds the gate shut.
Background & history
Sulphur mining began here in 1877, and the district that followed was shaped around it. Under one of the early operators, convicts from the Kushiro prison at Shibecha were sent onto the slope, where the sulphurous gas and dust blinded and damaged the eyes of the men working it. Later owners built a railway to move the ore off the mountain and a smelter to process it, and the workings passed through several hands before the last operation shut in 1963. The stripped ground underfoot is partly their doing rather than the volcano's alone.
Before you go
- Cash
- The car park is charged through the green season and opened free in winter, and the ticket also covers the Lake Mashu first lookout on the same day, which is the only day it is good for. The official pages do not state card acceptance, so carry cash.
- Before you go
- The hazard here is the gas rather than the ground: when a plume drifts your way the move is to step out of it, not to wait it out. The summit is closed to unaccompanied climbing after rockfall and slip accidents, and the environment ministry's own note says trekking there is by certified guide only.
- Another way
- The other way in is on foot. The Tsutsujigahara nature trail links the Kawayu Visitor Center to the mountain in about an hour one way with almost no gradient, running through belts of conifer, broadleaf, Iso-tsutsuji heath and creeping pine that swap over as the soil turns acid. The heath flowers white in June.
- After you get off
- There is no walking route from the station itself — the last stretch is road, and it ends in the car park at the foot of the bare slope. Where the tarmac stops the ground turns to pale gravel, and the nearest steam is a short walk out across it.