Karst landscapes are formed over time due to the chemical weathering and attrition of underlying limestone content. The chief culprit is acid rain, which produces carbonic acid, which dissolves the limestone content in the bedrock undrlying the soil. Karst landscapes are typified by an absence of vegetative growth, and almost barren appearance, and an absolute lack of ponds, streams, or other freshwater activity. The presence of sinkholes, while not always present, is another feature identifying karst landforms. The limestone constituent of the soil is dissoved, leaving the remaining soil particles to be washed away, which leaves a void in the ground. When the water level falls, the support mechanism for the soil on top is nonexistent, and the roof usually falls in, forming the sinkhole. The karst landscape can be a product of inefficient human management, but usually is the product of a natural weathering force on Earths surface.