Lake Mashu: Hokkaido’s transparent jewel │Hokkaido Japan

Lake Mashu is a lake located in Teshikaga Town, Kawakami District, Hokkaido, and is known as the second clearest lake in the world (Lake Baikal is number one).

Let’s explore why the lake is so transparent, looking at its origin and geographical characteristics.


Overview and characteristics of Lake Mashu

Lake Mashu is located in eastern Hokkaido, within Akan-Mashu National Park.

This lake is a caldera lake, created by a huge eruption 7000 years ago. In the Ainu language, it is called “Kintan Kamui To (Mountain God Lake)”, and there are various theories about the origin of that name.

There is a sheer caldera wall around 600 meters above sea level around the lake, and the lake is designated as a special protection area of Akan National Park.

Lake Mashu is a closed lake with no inflow or outflow rivers, and because the water level does not fluctuate much, it is thought that subsoil water flows into the nearby area.

The lake is extremely transparent and reflects little light other than blue, so on sunny days the surface of the lake is beautiful, giving it the nickname “Mashu Blue“.

The charm of Kamuish Island

Kamuishu Island (Nakashima), located almost in the center of Lake Mashu, is one of the lake’s most distinctive elements.

This island is the top of a dacitic lava dome over 210 meters high that appears above the lake surface, and its beautiful posture attracts many people.

“Kamuishu” means “a sublime spiritual being like a god” in the Ainu language, and according to Ainu legend, it was named by the Ainu based on the Ainu oral literature, Yukara.

The legend tells a mythical story about the island of Kamuish.

The wonder of a transparent lake

The transparency of Lake Mashu is astonishing, and a survey in 1930 recorded a clarity of 41.6 meters, surpassing that of Lake Baikal.

However, the transparency sometimes fluctuates, and there are various theories as to why.

The transparency of Lake Mashu may change in the future, so environmental protection is important.

Lake Mashu is a miracle of nature, and its beauty and wonder will move us.

Basic information about “Lake Mashu”

Basic InfoLake Mashu
Teshikaga Town, Kawakami District, Hokkaido

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