How were the Hawaiian islands formed? This big question was featured in a TV program of "National Geographic" early this year in Japan. According to the program, several undersea volcanos erupted many times at the position of Hawaii island and formed lands one after another. Those lands moved to the west and shaped into today's Hawaiian islands. This theory indicates that the western islands of Ni'ihau and Kauai islands are the oldest islands in the Hawaii islands and Hawaii island is the youngest. Actually, volcanic activities are still going on now on Hawaii island and lava is flowing into the sea and becoming new land.
When I was viewing the Hawaiian terrain map before the trip, I found two calderas on Oahu island other than Diamond Head. There is the globally biggest class of caldera in Japan, which is 25km in diameter in a south-north direction and 18km in an east-west direction. The calderas which I found on the map were not so big, and smaller than Diamond Head, but I wanted to visit them. One of them was the place which we visited next, the Punchbowl.
ハワイ諸島がどのようにして誕生したのか？ナショジオで解説があった。ハワイ島の位置で海底火山が噴火。できた陸地が少しずつ西へ移動することでいくつかの島が出来た、とあった。従って、ニイハウ島やカウアイ島が一番古く、ハワイ島が一番新しい島だという。なるほどハワイ島では今でも噴火が続いているし、溶岩が海に流れて土地を形成している。
渡航前、ハワイの地形図を眺めていてダイヤモンドヘッド以外のカルデラ地形を２つ見つけた。日本には南北２５ｋｍ、東西１８ｋｍの広大なカルデラ地形があるが、それには及ばないものの間違いなくカルデラ地形。２つとも実物を見てみたいと思った。その一つが次に訪れたパンチボウル。上手い名前を付けたものだ。昨日ハーフマラソンで走ったルートにパンチボウル通りという名前があったことを思いだした。通りの名前までキョロキョロ見ていた自分に改めて感心した。(^_^;)
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