MIGHT NOT ) KNOW … the answers !
( See Outdoor Focus Spring 2023 for the questions ) are formed in limestone and this dissolves when acid is present ( that ’ s the chemistry ). But the acid predominantly comes from bacteria or other organisms that live underground : microbes ( and bats , and birds and other animals ) respire and release carbon dioxide that is taken up by water , which becomes acidic and dissolves the rock . Guano releases ammonia ( bacterial action again ) and in some caves this is spread by draughts and even areas out of the reach of flowing water may be dissolved . Temperature affects rates of dissolution : in the UK , caves tend to be below 10 ° C , but tropical caves might record 30 ° C ( and what are known as ‘ hot caves ’ – those with extreme biological action from guano breakdown – can be much higher , and the higher the faster the chemical reactions ). The major ( and that really is major ) factor in cave formation is biology , which geologists might not appreciate , but there we are .
If you were wrong , think of the spellings : tites cling tight to the ceiling and mites crawl on the ground . Back to chemistry for a straw , where the deposition of calcite ( that makes cave formations ) relies on ‘ degassing ’ – that is , when the mineral-rich water droplet meets the air , the carbon dioxide it contains is released and the dissolved calcium carbonate is deposited as calcite , initially in a ring with the droplet in the middle . And this grows , with a hollow centre : a straw stalactite . Collectively , formations are called speleothems , by the way . One point for the formations , one for answering that a straw is a hollow stalactite .
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Phytokarst is unusual and again depends on biology . These formations are found in cave entrances , particularly in tropical caves , and are orientated towards the light . They appear as ‘ spikes ’, but these are not growing ; rather , the gaps between them are being eroded by cyanobacteria that make the pits deeper ( respiration again ). At least , that is the current theory . Phytogens are similar but different : these grow towards the light under the action of cyanobacteria that deposit minerals . If you answered with any concept of biological action making formations affected by light , award yourself two points for being exceptionally smart .
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When a cave passage is totally filled with water , it dissolves all the walls equally and a circular passage is formed below the water table , which is sometimes called the phreas ( a phreatic passage ). Later , if the water table drops , the water flows along the bottom of the passage as a stream and cuts downwards to produce a classic keyhole shape ( a vadose passage ). Two points if you got the concept right .
When a phreatic passage is totally filled with water , it flows slowly ;: vadose water flows quickly . Cavers use dye or lycopodium spores to trace the passage of water , releasing it at the sump and collecting it at known resurgences . By measuring the distance involved and the time taken , an estimate of the percentage of water-filled and air-surfaced passage can be made , producing an idea of how much passage is yet to be found . One point if you got the idea of tracing the flow of water ...
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One point for describing scallops as hollow ‘ scoop ’ shapes in passage walls , formed by eddies in flowing water . The steep side of the scallop lies upstream , indicating the way in which water once flowed even in nowdry and abandoned passages . A small size , perhaps down to 1cm long , indicates fast flow , while a metre long scallop signifies slow flow .
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One point for 1895 , the year that Gaping Gill was successfully descended by Édouard Martel , a Frenchman , using a rope ladder – quite an undertaking for such a long descent – and keeping in contact with the surface by telephone . The descent triggered a new era of sport as well as scientific exploration in caves . If you fancy your own visit , a winch with a safe seat is set up twice a year by caving clubs for the public to descend to the ( temporarily ) electrically lit main chamber at a measured depth of 104m .
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Cavers are potholers ... potholers are cavers ( though being named as a potholer is perhaps more traditionally applied to cavers in northern England , where many caves have a vertical entrance ( or ‘ pot ’). Speleology is the study of caves , hence speleologists . But an American coined the term ‘ spelunker ’, a name that cavers today eschew ( and consider rude ) as befitting untrained folk who enter caves and require rescuing . Or , it ’ s the sound that such people make when they fall : ‘ spelunk ’! One point each if you thought that cavers and potholers are the same , knew what a speleologist was , and you had any correct concept of spelunkers .
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