Lake Mashū
Interesting facts
- The caldera-forming eruption about 7,000 years ago threw out roughly 11 cubic kilometres of tephra and is rated 6 on the Volcanic Explosivity Index.
- With an average depth of about 137 metres, the lake holds close to 2.9 cubic kilometres of water.
- The lake surface lies about 351 metres above sea level, and its shoreline runs for nearly 20 kilometres.
- Sockeye salmon and rainbow trout live in the lake today, but both species were introduced by people.
- An alternative Japanese name, Mashin-ko, is written with characters meaning demon god, and one theory traces the name to the Ainu Mas-un-to.
- The volcano on the eastern rim was known to the Ainu as Kamuinupuri, the mountain of the gods.
- The crater slopes are wooded with Yezo spruce and Sakhalin fir, along with stands of Erman's birch.
- Sendoff Spring in the Pokémon Diamond and Pearl games, set in a region modelled on Hokkaido, is based on Lake Mashū.
- The lake lies within Akan-Mashū National Park, in the town of Teshikaga in eastern Hokkaido.
Why it is worth it
Lake Mashū sits at the bottom of a caldera in eastern Hokkaido, ringed by crater walls that drop about 200 metres to the water on every side. No river leaves it and only two small streams enter, so the lake loses water only by seepage, and there is no settlement or path on its shore: people see it from the rim, looking down into a closed oval of deep blue roughly six kilometres long. In the middle stands Kamuishu, a small island that is the tip of a lava dome, the only interruption on the surface.
The basin is young in geological terms. The present caldera was blown out by a large eruption about 7,000 years ago and the volcano stayed active until a last explosive eruption around 2,000 years ago; the peak of Mashū-dake still rises from the rim. The lake reaches 211 metres at its deepest, and its water became famous in 1931, when a transparency of 41.6 metres was measured, more than the figure then recorded for Lake Baikal. Clarity has since settled at around twenty to thirty metres, still enough to give the water its deep, almost inky blue.
Seeing it is not guaranteed. Fog fills the caldera on around a hundred days a year, and a well-known local saying holds that anyone who sees the lake clearly will meet misfortune. The Ainu called it Kintan-kamuy-to, "lake of the mountain god", shortened today to Kamuy-to. In winter, from roughly December to April, the surface freezes and the rim stands white above a sheet of ice. For a longer look, a trail of about 7 km follows the crater edge to the summit of Mashū-dake, two and a half to three hours each way.
Getting there
Lake Mashū is part of Akan-Mashū National Park in the town of Teshikaga. Nakashibetsu Airport (SHB) is about 36 km away, and the town of Nakashibetsu about 37 km. The lake is a 15–20 minute drive from JR Mashū Station in Teshikaga; Observatory No. 1 on the southern rim has parking, toilets and shops, and a few buses a day run there from the station, while Observatory No. 3 on the western rim, a short drive north, is reached only by car. The shore itself is closed to visitors.
On these lists
From the encyclopaedia
Lake Mashū is an endorheic crater lake formed in the caldera of a potentially active volcano. It is located in Akan Mashu National Park on the island of Hokkaido, Japan. It has been called the clearest lake in the world.
Wikipedia · CC BY-SA 4.0
43.58333, 144.51667per Wikidata