NEWSミシガン湖アメリカサイエンス

鮮やかなブルーの氷河がアメリカ・ミシガン湖に出現　なぜこんな色になるの？

アメリカ・5大湖の1つとして知られるミシガン湖に、鮮やかなブルーの氷河が現れた。
Hilary Hanson

アメリカ・5大湖の1つとして知られるミシガン湖。そこに掛かるマキナック橋の周辺に、鮮やかなブルーの氷河が現れた。

多くの人が、美しい氷河の写真をSNS上に投稿している。

地元・マキノーの住民リザ・シナーさんによれば、今回のような「スカイブルー」の氷河が現れることは珍しくないという。ミシガン・ライブが報じた。

しかしなぜ、このような「青い」氷河が現れるのだろうか？ 誰かが青いインクでも撒いたのだろうか？

国立雪氷データセンター（ NSIDC ）は氷に含まれる空気の量が原因だと説明する。

私たちが普段目にする雪や氷は、白く見える。これは雪や氷に多くの気泡が含まれているためで、氷の表面で全ての光波が跳ね返り、白く見える。

ところが、今回の氷河のように気泡が少ない場合、光波が氷の奥深くまで到達できる。その過程で波長の長い赤色が吸収され、波長の短い青色だけが反射。この結果、人間の目には氷が「青く」見えるのだ。

アメリカ国立公園局によれば、空気の量が少なく水の純度が高ければ高いほど、氷は青く見えるという。

この記事はハフポストUS版に掲載されたものを翻訳しました。

ハフポスト日本版はFacebookページでも情報発信しています。

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ANTARCTICA - 2010/10/18: Antarctica, Weddell Sea, Snow Hill Island, Emperor Penguins Aptenodytes forsteri, Chicks. (Photo by Wolfgang Kaehler/LightRocket via Getty Images) (credit:Wolfgang Kaehler via Getty Images)
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ANTARCTICA - 2010/10/20: Antarctica, Weddell Sea, Snow Hill Island, Emperor Penguins Aptenodytes forsteri, Group Of Chicks Walking On Ice Between Sattelite Colonies. (Photo by Wolfgang Kaehler/LightRocket via Getty Images) (credit:Wolfgang Kaehler via Getty Images)
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Open Image Modal
ANTARCTICA - 2009/10/30: Antarctica, Weddell Sea, Snow Hill Island, Emperor Penguin Colony Aptenodytes forsteri, Group Ofchicks Walking On Fast Ice. (Photo by Wolfgang Kaehler/LightRocket via Getty Images) (credit:Wolfgang Kaehler via Getty Images)
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Open Image Modal
ANTARCTICA - 2009/10/26: Antarctica, Weddell Sea, Snow Hill Island, Emperor Penguin Colony Aptenodytes forsteri, Group Of Chicks. (Photo by Wolfgang Kaehler/LightRocket via Getty Images) (credit:Wolfgang Kaehler via Getty Images)
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Open Image Modal
ANTARCTICA - 2009/10/30: Antarctica, Weddell Sea, Snow Hill Island, Emperor Penguin Colony Aptenodytes forsteri, Chicks On Ice. (Photo by Wolfgang Kaehler/LightRocket via Getty Images) (credit:Wolfgang Kaehler via Getty Images)
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Open Image Modal
ANTARCTICA - 2009/10/30: Antarctica, Weddell Sea, Snow Hill Island, Emperor Penguin Colony Aptenodytes forsteri, Close-up Ofchick. (Photo by Wolfgang Kaehler/LightRocket via Getty Images) (credit:Wolfgang Kaehler via Getty Images)
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Open Image Modal
ANTARCTICA - 2009/10/30: Antarctica, Weddell Sea, Snow Hill Island, Emperor Penguin Colony Aptenodytes forsteri, Close-up Ofchick. (Photo by Wolfgang Kaehler/LightRocket via Getty Images) (credit:Wolfgang Kaehler via Getty Images)
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Open Image Modal
ANTARCTICA - 2009/10/30: Antarctica, Weddell Sea, Snow Hill Island, Emperor Penguin Colony Aptenodytes forsteri, Close-up Ofchick. (Photo by Wolfgang Kaehler/LightRocket via Getty Images) (credit:Wolfgang Kaehler via Getty Images)
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Open Image Modal
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Open Image Modal
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Open Image Modal
1, ANTARCTICA - 1994/01/01: Antarctica, Riiser-larsen Ice Shelf, Emperor Penguin Colony, Adult With Chicks. (Photo by Wolfgang Kaehler/LightRocket via Getty Images) (credit:Wolfgang Kaehler via Getty Images)
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Open Image Modal
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Open Image Modal
1, ANTARCTICA - 1994/01/01: Antarctica, Riiser-larsen Ice Shelf, Emperor Penguin Colony, Chicks Forming Creche. (Photo by Wolfgang Kaehler/LightRocket via Getty Images) (credit:Wolfgang Kaehler via Getty Images)
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Open Image Modal
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Open Image Modal
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Open Image Modal
ANTARCTICA - 2009/10/30: Antarctica, Weddell Sea, Snow Hill Island, Emperor Penguin Colony Aptenodytes forsteri, Adults With Chicks. (Photo by Wolfgang Kaehler/LightRocket via Getty Images) (credit:Wolfgang Kaehler via Getty Images)
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Open Image Modal
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Open Image Modal
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Open Image Modal
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Open Image Modal
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Open Image Modal
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Open Image Modal
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Open Image Modal
ANTARCTICA - 2010/10/20: Antarctica, Weddell Sea, Snow Hill Island, Emperor Penguins Aptenodytes forsteri, One Chick Walking On Ice Between Sattelite Colonies. (Photo by Wolfgang Kaehler/LightRocket via Getty Images) (credit:Wolfgang Kaehler via Getty Images)
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Open Image Modal
ANTARCTICA - 1993/01/01: Antarctica, Livingston Island Hannah Point, Close-up Of Chinstrap Penguin Chick. (Photo by Wolfgang Kaehler/LightRocket via Getty Images) (credit:Wolfgang Kaehler via Getty Images)
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Open Image Modal
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