There are over a hundred active volcanoes in Japan with almost half showing worrying signs of erupting in the future. One of these is a mountain called Kusatsu-Shirane which is located in Kusatsu, Gunma. Its last recorded major eruption dates back to 1983 and has since produced several overlapping cones and three crater lakes. The most impressive of all craters is Yu-gama which is stunningly gorgeous with its emerald green water.
Yu-gama is primarily the main attraction of Mt. Shirane. Its name literally means “hot water pot.” It is considered to be one of the most acidic lakes in the world and the largest of all Mt. Shirane’s crater lakes. It measures approximately 300 meters wide and 30 meters deep with a temperature of 18 degrees Celsius. Due to its high acid level, it is impossible for plants to grow around the caldera of the lake.
Over a hundred years ago, Yu-gama’s temperature used to reach boiling point. But in recent years, the lake remains at only a warm temperature. The underwater vents of the lake controls the surrounding temperature by making sure that it is always warmer than the rest. The lake is a stunning site with its turquoise-blue expanse of water. The color is brought about by its acidity and high sulfurous fumes which are devoid of the existence of any life form in the surrounding area. This comes from the acidic streams draining down from the mountain to the other parts, including the lake.
Getting to the place is very easy. From the Kusatsu Bus Terminal Stop, catch a bus going to Shirane Rest House. It usually takes 30 minutes one way. Then it is a 10-minute walk to reach the lake. Otherwise, a quicker way is to ride up the mountain on the Shirane Volcano Ropeway which takes around eight minutes. However, take note that the road leading to Kusatsu-Shirane is closed during winter. There is also nearby accommodation at the Kusatsu Ski Resort which provides a great opportunity to explore the surrounding area.
Upon reaching the top, you will be rewarded with amazing views of Yu-gama Lake’s baby blue color! This is one of the real beauties of the mountain ranges that you wouldn’t want to miss in Kusatsu.