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Onneto Hot Falls and springs (Yuno-taki waterfall)

Onneto Hot Falls, Japan
Onneto Hot Falls / アラツク, Wikimedia Commons / CC BY-SA 4.0

WorldBlue  In short

Onneto Falls are not usual at all – this waterfall is hot! And even more: this is a unique natural laboratory where is ongoing the formation of manganese ore!

4.1 out of 10 stars 40.8%

GPS coordinates
43.3700 N 143.9783 E
Location, address
Asia, Japan, Hokkaidō, Akan National Park, to the south-east from Onneto Lake
Mineral springs, Thermal springs, Waterfalls, Ecosystems
Name in Japanese
オンネトー湯の滝 (Onnetō Yu-no-Taki, from Ainu, where onne = ancient and to = lake)
Alternate names
Onnetō Falls, Yuno-taki Falls, Yunotaki waterfall
˜ 30 m

Map of the site

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WorldYellow In detail

Akan National Park

If we imagine Japan as a densely populated, urbanized country, this is not true for most parts of Hokkaido Island – an island which for the most part is covered with forest, often – a pristine forest with lakes, mires, volcanoes, hot springs, waterfalls and other wonders of nature.

National parks were created here fairly early and one of the first was Akan National Park which was founded in 1934. This is a gorgeous natural area with its own volcanoes and several gorgeous lakes with unusually lucid water.

Hot waterfall

Onneto Falls is just one more natural wonder in this beautiful area. In fact, in this area are found several waterfalls but the best known are Onneto Hot Falls – some 30 m tall waterfall created by hot springs. The temperature of its water is 43° C. Water from the springs divides into smaller trickles which flow down among moss-covered blocks of volcanic andesite rock.

Earlier the pond below the falls was used as a public bath but this was discontinued after in 1989 there was discovered that the black mud in the springs and waterfall contains lots of manganese with specific colonies of microorganisms and algae. Thus it is an unusual monument of nature and in 2000 it was designated a natural monument.

Below the falls is a pond with fish where earlier tropical fish was released using the opportunity of naturally heated water. Later it was found out that this fish adversely affects the development of the unique manganese deposits.

Unique mine of manganese ore

The black mud in the falls and in the pond is not usual – it is manganese ore. Every year these springs create some 1.1 tons of manganese oxide and over the last 4 – 5 thousand years the layer of manganese oxide has reached the thickness of approximately one meter.

Research shows that the formation of manganese ore from the spring water is facilitated by specific manganese-oxidizing bacteria and filamentous algae.

Onneto Falls and spring represent a unique opportunity for the research of the formation of manganese ore.

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