流石

流石（英語：flowstone）是指一種由方解石或其他碳酸鹽礦物組成的片狀沉積物，形成於水流經過的洞穴牆壁或地板的地方^[1]。在石灰岩的“溶洞”中最常見。然而，它們也可能在任何類型的洞穴中形成。只要進入到這些洞穴中的水含溶解的礦物質就可。流石是在包气带中地下水脫氣形成的^[2]。

形成

當水沿著地面或傾斜壁向下移動時，在途徑會形成一層水膜 ^[3]。溶解在水膜中的碳酸鈣（方解石）、文石、石膏、^[4]^[5] 或其他礦物，會被沉澱出來。這是因爲溶解在水中的礦物質，因爲水的流動而失去其溶解中的二氧化碳，導致水中酸性減低，礦物質的溶解度也減低，而沉澱出來，當這些沉澱物的薄層相互堆積時會形成流石，有時會隨著沉澱物變厚而形成更圓的形狀。

流石有兩種常見的形式，石灰華和洞石。石灰華通常是經由碳酸鈣沉澱形成，呈海綿狀或多孔狀。洞石是一種碳酸鈣沉積物，通常形成於小溪或河流中，是層狀的，包括石筍和钟乳石等結構。

碳酸鈣沉積物可堆積成薄片，稱為“窗簾”，一般是從洞穴牆壁懸垂下來像窗簾。有些窗簾是半透明的，有些有棕色和米色層，看起來很像培根（通常稱為“洞穴培根”）。

雖然流石是洞穴最大的沉積物之一，但它們仍然可以被觸摸損壞。人手指上的油會導致流動的水避開該區域，不能形成水膜然後該區域變乾。流石也是過去乾旱時期的良好標識，因為流石需要水才能形成；長時間缺水就不會形成流石。所以流石的存在與否及其詳細結構，可用來推斷古氣候歷史^[2]。

參考文獻

^ Hill, C A, and Forti, P, (1997). Cave Minerals of the World, (2nd edition). [Huntsville, Alabama: National Speleological Society Inc.] p.70
^ ^2.0 ^2.1 Drysdale, Russell; Zanchetta, Giovanni; Hellstrom, John; Maas, Roland; Fallick, Anthony; Pickett, Matthew; Cartwright, Ian; Piccini, Leonardo (2006). "Late Holocene drought responsible for the collapse of Old World civilizations is recorded in an Italian cave flowstone". Geology. 34 (2): 101. Bibcode:2006Geo....34..101D. doi:10.1130/G22103.1.
^ Smith, G.K., (2016). “Calcite Straw Stalactites Growing From Concrete Structures”, Cave and Karst Science, Vol.43, No.1, P.4-10, (April 2016), British Cave Research Association, ISSN 1356-191X.
^ Hill, C A, and Forti, P, (1997). Cave Minerals of the World, (2nd edition). [Huntsville, Alabama: National Speleological Society Inc.] pp 193 and 196
^ Szablyár, P., (1981) “Morphogenetics of Umm al Massabih Cave (Libya)”, Karszt és Barlang, No. 1, P27-34. In Hungarian. White W.B., (1997), “Color of Speleothems”, Cave Minerals of the World, (2nd Edition) Hill C. and Forti P. [Huntsville, Alabama: National Speleological Society Inc.] 239-244

[”Hill”-1] Hill, C A, and Forti, P, (1997). Cave Minerals of the World, (2nd edition). [Huntsville, Alabama: National Speleological Society Inc.] p.70

[”Drysdale”-2] 2.0 ^2.1 Drysdale, Russell; Zanchetta, Giovanni; Hellstrom, John; Maas, Roland; Fallick, Anthony; Pickett, Matthew; Cartwright, Ian; Piccini, Leonardo (2006). "Late Holocene drought responsible for the collapse of Old World civilizations is recorded in an Italian cave flowstone". Geology. 34 (2): 101. Bibcode:2006Geo....34..101D. doi:10.1130/G22103.1.

[”Smith”-3] Smith, G.K., (2016). “Calcite Straw Stalactites Growing From Concrete Structures”, Cave and Karst Science, Vol.43, No.1, P.4-10, (April 2016), British Cave Research Association, ISSN 1356-191X.

[”Hill，C”-4] Hill, C A, and Forti, P, (1997). Cave Minerals of the World, (2nd edition). [Huntsville, Alabama: National Speleological Society Inc.] pp 193 and 196

[”Szablyár”-5] Szablyár, P., (1981) “Morphogenetics of Umm al Massabih Cave (Libya)”, Karszt és Barlang, No. 1, P27-34. In Hungarian. White W.B., (1997), “Color of Speleothems”, Cave Minerals of the World, (2nd Edition) Hill C. and Forti P. [Huntsville, Alabama: National Speleological Society Inc.] 239-244

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