Peer into the transparent depths of Lake Mashu
Lake Mashu is renowned for the crystal clarity of its waters. Because no rivers or streams feed it or flow out from it, silt, algae, and other forms of suspended matter do not cloud the water. Its waters, which consist almost entirely of rainwater, have a deep blue hue so special that it is termed “Mashu blue.”
Fog on the lake
Fog forms close to the surface of Lake Mashu frequently throughout the year. During the peak season from May to October, the lake is wholly visible for an average of 137 days, semi-visible for 54 days, and obscured for 29 days (estimates are based on data from 2008 to 2018). The fog is at its thickest in June and July. During this period, the lake is only completely visible for an average of 15 days. The weather around the lake can transition from bright and sunny to dark and foggy within minutes.
Kamuishu, Lake Mashu’s only island, is a pillar of lava that rises some 240 meters from the lakebed. Only the top 30 meters break through the water’s surface. This visible tip of Kamuishu measures only about 500 square meters.
Mashu Third Observatory
If you look at Lake Mashu from Kawayuonsen、the first thing you will see is Mashu Third Observatory。If you look closely at Kamuishu Island you can see Lake Mashu from a different perspective from the first observation deck. On the other side of the lake is Iozan mountain, Lake Kussharo and Mokoto Mountain, and the Kussharo Caldera, all of these creating a dynamic wide view. You can also take a look at the beautiful alpine nature as it changes through the year.
※Observation deck and parking are FREE
An observation deck located on the border of the towns of Kiyosato and Nakashibetsu. Thick trees are surrounding the deck, so it is difficult to get a wide view however, first if you compare this with Mashu Third Observatory, because of low altitude, the nearby lake surface creates a fog effect. If you look from the other side, Lake Mashu and Mashu Mountain have a different ambiance. There are not many visitors, so you can fully enjoy the serene and calm lake view.
※Toilet facilities (only during summer)
※Only open from April to November as it is closed in winter