Caves and the Subterranean World

Mountains symbolise the zenith of human aspiration while caves are linked with depths of the power of darkness and depravity. It is a stupid association as for thousands of years; caves have provided basic shelter for both man and animals. Caves are also attractive and colourful. Most of the caves have been formed in limestone rock or dolomite. These rocks are sedimentary because they are laid down in layers which are successive. They become susceptible to vertical cracking. Water that seeps down these vertical faults works its way along the bedding planes and it wears away the rock. It results in the formation of sink holes and horizontal caverns. Changes in these water tables have left some caves very dry but many have rivers running through them and they help feed large underground lakes and subterranean waterfalls. Diving apparatus is required at many places to explore these caves. Most caves are damp as water seeps through cracks and joints in their roofs or trickles down their walls. This water is coming through the limestone layers and it starts to dissolve some of the lime. When the water evaporates, it leaves traces behind of calcium carbonate that builds up over a period of time. Some of the calcium carbonate gets deposited at points in the ceilings where the water drips while the remainder falls to floors of the caves. As a result of this, hanging deposits or stalactites and standing deposits or stalagmites are formed. If these formations are allowed to grow for longer periods of time, they will unite and columns will be formed, usually clustered together in styles of music organ pipes. Some caves will form as a result of volcanic activity. This is because the hot lava flows from a fissure and will cool rapidly when exposed to the air and it will harden on the surface while the molten lava flowing underneath drains away, leaving a cavity. There are caves of this type in Hawaii and Iceland. Few caves are a result of water erosion, mostly from the sea and they can take on several varieties of shapes. Their rocks are not always of the same hardness. Waves that hit the cliff will soon cut into rocks which are softer than their surroundings and are likely to erode horizontal or vertical joints. Waves that crash into deep caverns will compress the air within them and this makes the rock loose at weak points in the roofs. A natural chimney or blow hole is formed at some distance back from the face of the cliff. When the arch collapses, a vertical stack will be left and an example of this is the Old Man of Hoy cliff in the Orkney Scottish Islands. The temperature in caves remains mostly constant at about fifty degrees Fahrenheit and this is a boon to many animals, particularly bats. Such kinds of caves are found on the French Riviera, Spain, the Middle East and the Philippines. A remarkable bat cave is the one in Texas USA – the Ney Cave and it is presumed to give shelter to almost fifteen million bats. Other interesting specimens are the columns that guard the entrance to Fingal’s Cave (also made popular by Felix Bartholdy Mendelssohn’s haunting and mystical overture). This cave is located on the island of Staffa, Inner Hebrides, Scotland in the United Kingdom. The columns may look like Masonic work to you but they are a natural formation of basalt which split in this fashion thousands of years ago. Typical limestone formations in caves could be seen in the Tillywhim Caves in Dorset near Swansee. In this case, water has penetrated through the fissures in the rock. The channels have enlarged gradually and they have created underground rivers. The rivers dried up eventually and became dry and their mouths got exposed by the fall and the erosion of the rocks along the coast of the sea.