Hakone’s “Great Boiling Valley”
Apparently, before getting the name Owakudani, “Great Boiling Valley,” this area of Mount Hakone was known as Ojiguko, “Great Hell.” Both work, though the latter fits better with the pictures I took on the day R. and I visited: hooded figures moving slowly through sulphurous steam and boiling milky mudpots.
Mount Hakone last erupted in 950 BC. “However, solfataric activity can still be found at four places on the northern and northeastern sides of Kami-yam and the northeastern side of Komaga-take, just southeast of Kami-yama.”
BTW, if you’re interested in a guidebook that combines detailed — if dated, it was last updated in 1988 — explanations of Japan’s volcanic geography, check out Paul Hunt’s Hiking in Japan: An Adventurer’s Guide to the Mountain Trails. The book is out of print, but you may be able to check it out of your library. Or, if you’re stuck, you can borrow mine 🙂