About: Mount Kusatsu-Shirane (草津白根山, Kusatsu Shirane-san) is a 2,165 m (7,103 ft) active stratovolcano in Kusatsu, Gunma, Japan. It is called Kusatsu Shirane to differentiate it from the Mount Nikkō-Shirane on the other side of Gunma Prefecture.
On January 23, 2018, a minor phreatic eruption of the volcano occurred. One person was killed, and others were injured in an avalanche triggered by the eruption.The next day, new activity forced police to suspend search operations. One month after the eruption, it was announced by prefectural officials that only the summit of the volcano was off limits to the public. (Sourced from Wikipedia)
Geologic Summary: The Kusatsu-Shiranesan complex, located immediately north of Asama volcano, consists of a series of overlapping pyroclastic cones and three crater lakes. The largest of these is Yu-gama, an acidic emerald green lake with rafts of yellow sulfur sometimes seen floating on its surface. The andesitic-to-dacitic volcano was formed in three eruptive stages beginning in the early to mid-Pleistocene. The Pleistocene Oshi pyroclastic flow produced extensive welded tuffs and non-welded pumice that covers much of the E, S, and SW flanks. The latest eruptive stage began about 14,000 years ago. Historical eruptions have consisted of phreatic explosions from the acidic crater lakes or their margins. Fumaroles and hot springs that dot the flanks have strongly acidified many rivers draining from the volcano. The crater was the site of active sulfur mining for many years during the 19th and 20th centuries. (Source: Smithsonian Global Volcanism Program https://volcano.si.edu/volcano.cfm?vn=283120)
My Visit: Given the main trail to view Yugama was closed off, I did not use AllTrails and instead did the short walk around Yumiike which I also decribe on volcanicjapa.com website here: https://volcanicjapan.com/ive-explored/f/%E8%8D%89%E6%B4%A5%E7%99%BD%E6%A0%B9%E5%B1%B1—kusatsu-shirane-yugama-%E6%B9%AF%E9%87%9C-manza-onsen—10302022
After taking a one day break post Asama hike, I decided rather last minute to remain in Gunma Prefecture. The weather was starting to rapidly change at altitude which was limiting my options depending on the day. I drove a few hours from central Takasaki to Mount Kusatsu-Shirane. Kusatsu Onsen is one of the most premier onsen towns in Japan however many places were fully booked and prices were rather high, so I decided to stay in a more remote area not too far from Kusatsu called Manza Onsen (where I made reservations for).
For this trip I was keen on seeing Yugama 湯釜 which as described above, is the acidic emerald green lake however due to volcanic activity, the area was closed off so instead I took in what I could see and decided for a short hike around Yumiike 弓池 which is directly across highway 272 from Yugama. Other than an ice cream and small souvenir shop, there was not much else I could do so I chalked this up to a half visit and will need to try back at another time.
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