After explaining what volcanoes are like in isolation, I now want to explain how these dynamic, active, furious, temperamental mountains lurk within the Japanese Alps, bursting forth in all their magnificent starkness to create a unique mountain landscape.
|Eruption of Yake-dake in 1925|
Tucked away at the bottom of these mountain walls, Kami-kōchi’s flat valley floor is equally renowned for the beauty of its woods and waters. Yet the beauty of these emerald waters and the verdant woods all testify to the fact that Kami-kōchi, together with its surrounding scenery, was formerly a lake – and one that owed its existence to the activity of a volcano.
For it was here that the Shiratani volcano erupted, an outlier of the Iodake volcano (also known as Yake-dake), which is an extension of the Norikura ridge within the Ontake volcano chain. Together with those of Iodake itself, these eruptions dammed up the rivers flowing along the contact line of the Chichibu Paleozoic strata and the granites of the Azusa River fault zone and created a lake of considerable depth, according to a certain geologist.
In this way, the effusions of the Iodake volcanic group pent up a mighty lake, but in time the waters of the lake made a breach, creating today’s Takahara (or Jinzū) River and the Azusa River (a tributary of the Shinano River), with Iodake as the intervening watershed.
For its part, the lake dried out into islands, river plains, and hillocks. Even after creating today’s Kami-kōchi, though, Iodake has continued to shape the valley, sending down mudflows to block the river anew, creating a secondary lake in the entrancing form of Tashiro Pond, where in autumn the withered leaves of the willows sway yellowing to and fro as coveys of ducks sweep in to fish the shallows.
In this peaceful valley, the verdant forests have taken root in the rich soils bequeathed by the volcanic rubble and, on the first floor of the hot spring building, patrons in their bathrobes sit around gazing up at the cliffs of Hodaka and Kasumizawa-dake and have nothing better to do than complain about the food. But they should never forget that it was a volcano that made their easy chatter possible, by creating the backdrop for it.
Beta translation from Kojima Usui, Characteristics of the Japanese mountain landscape (日本山岳景の特色), originally published in "Nippon Arupusu (1910), Vol IV, reprinted in Nippon Arupusu, Iwanami Bunko edition, 1992.
Thanks for bringing this to my attention. I had not read of an ancient lake in the Kamikochi vicinity. Of course the scenario fits in perfectly with other lakes of volcanic cataclysmic origin such as the Fuji Five Lakes and the lakes of Ura Bandai. How interesting to consider that there was a lake "of considerable depth" in the area at some distant (or not so distant) time in the past.
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