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LANDFORMS AND THEIR EVOLUTION 53 from a less than half a metre to thirty metres Depositional Landforms or more. Some of these form solely through Many depositional forms develop within the solution action (solution sinks) and others limestone caves. The chief chemical in might start as solution forms first and if the limestone is calcium carbonate which is easily bottom of a sinkhole forms the roof of a void or cave underground, it might collapse leaving soluble in carbonated water (carbon dioxide absorbed rainwater). This calcium carbonate a large hole opening into a cave or a void is deposited when the water carrying it in below (collapse sinks). Quite often, sinkholes solution evaporates or loses its carbon dioxide are covered up with soil mantle and appear as it trickles over rough rock surfaces. as shallow water pools. Anybody stepping over such pools would go down like it Stalactites, Stalagmites and Pillars happens in quicksands in deserts. The term Stalactites hang as icicles of different doline is sometimes used to refer the collapse sinks. Solution sinks are more common than diameters. Normally they are broad at their collapse sinks. Quite often the surface run- bases and taper towards the free ends off simply goes down swallow and sink holes showing up in a variety of forms. Stalagmites rise up from the floor of the caves. In fact, and flow as underground streams and re- stalagmites form due to dripping water from emerge at a distance downstream through a cave opening. When sink holes and dolines the surface or through the thin pipe, of the join together because of slumping of materials stalactite, immediately below it (Figure 6.9). along their margins or due to roof collapse of Stalagmites may take the shape of a caves, long, narrow to wide trenches called column, a disc, with either a smooth, rounded bulging end or a miniature crater like valley sinks or Uvalas form. Gradually, most of the surface of the limestone is eaten away by these pits and trenches, leaving it extremely irregular with a maze of points, grooves and ridges or lapies. Especially, these ridges or lapies form due to differential solution activity along parallel to sub-parallel joints. The lapie field may eventually turn into somewhat smooth limestone pavements. Caves In areas where there are alternating beds of rocks (shales, sandstones, quartzites) with limestones or dolomites in between or in areas where limestones are dense, massive and occurring as thick beds, cave formation is prominent. Water percolates down either through the materials or through cracks and joints and moves horizontally along bedding planes. It is along these bedding planes that the limestone dissolves and long and narrow to wide gaps called caves result. There can be a maze of caves at different elevations depending upon the limestone beds and intervening rocks. Caves normally have an opening through which cave streams are discharged. Caves having openings at both the ends are called tunnels. Figure6.9:Stalactitesandstalagmitesinlimestonecaves Reprint 2026-27