A note on spelling... the proper name is Tōya-ko which should be written as Touya-ko. You will often see the "u" omitted, to leave just Toya-ko. Youtei-zan is another example where this occurs. This occurs all the time in English web translation of Japanese names.
From Youtei-zan, it's another 50+ km to get to Toya-ko
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The volcanic story of Touya-ko is far from over however... back in 2000, Usu-yama (actually it was the nearby connected volcanic cone, Nishi-yama) erupted in a spectacular display of force. This volcanic system has erupted every 20-50 years since the 1600's when it awoke from slumber.
The eruption was announced by pronounced activity around 31st March - with major land deformation and crater formation by the 5th April with activity peaking around the 7-10th April. The volcano continued till about June...
At the top you'll get amazing views across both the Touya lake...
The views out across Uchiura Bay are glorious. It's the Pacific Ocean ... and it's beautiful.
And another view of Uchiura Bay, with volcanic steam venting through Usu-zan's top.