MASHU / KUSSHARO
Lake Mashu is a caldera lake created by Mashu Volcano. No rivers flow in or out of the lake. As the lake is surrounded by steep cliffs, it is hard to get to it. This is one reason why it is very transparent. Its degree of transparency (visibility) was to a depth of 41.6 meters in 1931, which was the world’s record, but it has gradually declined to 22.5 meters as of 1999.
It is also called Fog Lake, because fog often rises, which makes seeing the entire lake difficult. This only adds to the lake’s mysteriousness. On clear days, the transparent deep blue water offers a breathtakingly beautiful sight. You can enjoy views from the first and third observatories. A small island can be seen in the center of the lake rising only 31 meters high on the water, but this is actually the tip of a 243-meter volcano hidden under the water.
Lake Kussharo, with an area of 79.7 square kilometers, is the second largest lake in Hokkaido and the sixth largest in Japan. Scores of hot springs are located near the lake and also in the lake. As a part of the lake does not freeze, thanks to the hot springs in the lake, swans come here in winter. Because the acidity of the lake’s water is high, few fish live in it and few waterweeds grow.
Mount Io-zan (“Sulfur Mountain”) is an active volcano, as evidenced by its rough-looking, brown-colored surface. Gas belches out from innumerous solfataras and the area smells sulfurous. This is a different mountain from Mount Io-zan in the Shiretoko Peninsula.