ABSTRACT
29 Subsidence on Limestone Limestone is the only common rock soluble in water. It dissolves in rainwater enriched by carbon dioxide derived from organic soils so the processes and results are on a larger scale in areas of warm, wet climate. Karst features are erosional forms produced by solution on bare rock surfaces, beneath the soil at rockhead, and within the rock. Solution is highly selective, so that most joints are etched out to create fissures, gullies and caves; they may be full of air, water or soil, between remnant blades of strong, unweathered rock. This creates the highly variable ground conditions which typify limestone areas. Pinnacled rockhead descr ibes a highly f issured limestone surface beneath a soil cover. Tall, narrow, unstable or loose pinnacles may be supported only by the soil, and fissures may extend far below into caves. Rockhead relief in tropical areas may be > 20 m.
