What you can see on the Atosanupuri cams
Atosanupuri is a place of contrast: forested domes beside bare, whitish slopes where nothing grows, and steam rising from vents ringed by a pale crust of deposits. On cold mornings steam can rise from several points along the slope at once; on a warm afternoon the same vents can be almost invisible. The bare ground stays the same through the year, and what changes is the green around it and how much steam the cold air makes visible.
A wooded dome beside the bare sulphur slopes
From the flat ground at the north-east foot of Atosanupuri, the camera looks across a strip of grass and a line of trees to the domes of the volcano. The rounded dome in the centre is covered in forest, but on the left the ground changes completely: a bare, whitish slope where nothing grows. Tall conifers rise in front on the right, and deciduous trees line the foreground.
That contrast between the green dome and the bare ground is what this wide view shows best, while the second camera goes in close to the vents themselves. On cold mornings steam can rise from several points along the slope at once.
Steam vents at the foot of a dark dome
Much closer than the view from the north-east foot, this camera stands among the low scrub that covers the ground almost up to the vents. A dark, rounded dome fills the centre of the frame. At its left foot, white deposits and steam mark a group of vents, and more show on the right, where the dome meets a steep, bare slope rising out of the frame. Patches of stony ground break up the scrub in the foreground.
At this distance the pale crust left around each vent is easy to make out. The steam shows best in cold air; on a warm afternoon the same vents can be almost invisible.
A mountain that paid for a railway
Sulphur was mined here industrially from the 1880s, and it was profitable enough that the money built the railway down to Kushiro on the coast. The work was brutal — much of it done by convict labour — and it went on until 1963. The remains of the workings are still on the slope. The Japanese name for the hill, Iōzan, simply means sulphur mountain.
When to watch Atosanupuri
Japan is nine hours ahead of UTC all year. The steam is at its most dramatic in winter and on cold mornings, when the air can hold less water; on a warm summer afternoon the same vents are almost invisible. Hokkaido winters are long here, with snow on the ground from November to April — though not on the hot parts of the slope, which stay bare.
Around Atosanupuri
Kawayu Onsen is a few minutes away, a hot spring town whose water comes from this hill and is acidic enough to be sharp on the skin. Lake Kussharo, the largest caldera lake in Japan, is on one side and Lake Mashū, famous for its clarity and for being hidden in fog, on the other. All of it is Akan-Mashu National Park.
Visiting Atosanupuri
You can walk right up to the vents: a path from the car park reaches ground where the rock is hot and the gas is strong, with no barrier beyond a rope. It is one of the few places in Japan where a fumarole field is that accessible. Keep to the marked ground, and do not linger in a hollow where the gas can pool.
