We took a day trip to Hachimantai National Park, the highlight of which is Goshogake, one of my favourite places in Japan. Goshogake is a mud volcano / onsen that remains totally unknown for most people in Japan. It is quite remote, though there is a bus that comes through several times a day, and access can be difficult in winter. It's relatively close to Tamagawa onsen, perhaps a 5km hike - longer by road (see map below).
|Steaming sulfur rising|
|Mud piles in a pond|
|Walking paths trails - to Hachimantai, Tamagawa and Onuma.|
|The signs there urge people to stay on the walking path because|
of the potential for subsidence. They are faced with the situation that
the walking trails themselves can become dangerous.