Lake Kussharo

Lake Kussharo (屈斜路湖, Kussharo-ko) is a caldera lake in Akan National Park, eastern Hokkaidō, Japan. As with many geographic names in Hokkaidō, the name derives from the Ainu language. It is the largest caldera lake in Japan in terms of surface area, and the sixth largest lake in Japan. It is also the largest lake in Japan to freeze over completely in winter. The name Lake Kutcharo is also sometimes used.[2][3]

Relief map of Kussharo Caldera (left) & Mashu Caldera (right)

Lake Kussharo 屈斜路湖
July 2013
Lake Kussharo 屈斜路湖
Location	Teshikaga, Hokkaidō
Coordinates	43°37′39″N 144°19′46″E
Type	acidotrophic crater lake
Primary inflows	Atosa River (跡佐川, Atosa-gawa), Amemasu River, Onnenai River, Shikerepenbetsu River, Onneshireto River, Toikoi River, Meshikimemu River, Enetokomappu River, Ossappe River (尾札部川, Ossappe-gawa)
Primary outflows	Kushiro River (釧路川, Kushiro-gawa)
Basin countries	Japan
Surface area	79.3 km2 (30.6 sq mi)
Average depth	28.4 m (93 ft)
Max. depth	118 m (387 ft) [1]
Water volume	2.25 km3 (0.54 cu mi)
Shore length1	57 km (35 mi)
Surface elevation	121 m (397 ft)
Islands	Nakajima
Settlements	Kawayu Onsen and Kotan in Teshikaga
References	[1]
1 Shore length is not a well-defined measure.

The lake's central island, Nakajima (not to be confused with another island of the same name in Lake Tōya), is a stratovolcano. It is also Japan's largest recursive island. Volcanic gases render the lake water acidic, and it supports few fish, except in areas where inflowing streams dilute the water. Rainbow trout, which are resistant to fairly acidic water, have been artificially introduced. In 1951, a rare form of cicada (Hyalessa maculaticollis) was discovered, and is now protected by the government. The lake is also on the migratory path of the whooper swan.

Along the lake shore are several outdoor hot springs and a sand beach, with naturally heated sand and hot groundwater. Wakoto Peninsula, extending into the lake, has a number of active sulfurous vents.

The lake is also known as "Japan's Loch Ness", after numerous reported sightings on a lake monster, dubbed Kusshii by the press from 1973.

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  Viewed from Tsubetsu Mountain pass
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  Viewed from Mt. Mokoto Prospects Park
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  Nakajima island (Lava dome)
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  Whooper swans at Lake Kussharo