チョーク (岩石)







ドーヴァーの白亜の崖


チョーク (chalk) は、未固結の石灰岩のこと。イギリスのドーバー海峡周辺で崖をつくる厚い地層のことで、円石藻の化石（炭酸カルシウムのココリス）から成る。


日本語では白亜（はくあ、白堊とも）という。日本では地層が堆積した年代から、白亜紀の語源となったほか、黒板に用いるチョーク（白墨）の語源にもなっている。



関連項目





ウィキメディア・コモンズには、チョークに関連するカテゴリがあります。



  • 岩石 - 堆積岩 - 石灰岩

  • 岩石の一覧

  • 鍵層








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