Lapies or minor solution features form as water weathers the rock surface. Lapies are not as evident as the various major landforms, and normally appear in the later stages of karstification. Because of the small scale at which lapies form, these features must be identified by closer examination. Many factors control, however, the formation of lapies. One of the most important is the ground cover -- soil, vegetation, surficial deposits. Lapies are more common in the carbonate rocks (limestone and dolomite) where chemical solution occurs. In the evaporite rocks, the mechanical weathering often proceeds faster than the formation of lapies so that the minor solution features may not form.
On bare ground, the water can directly attack the entire surface of the bedrock. Some features form by direct rain impact, while others form as the rainfall collects and runs off.
On partially covered karst, the water action is directed by the soil. However, part of the rock is attacked directly by the rainfall and runoff while the covered positions are not. The cover will retain some of the water allowing sustained solution.
In covered lapies, the soil acts like a sponge to keep the water in contact with the bedrock. Because the water is not free to move over the rock, the development of the covered lapies is strongly controlled by structure (joints, cleavage, bedding). These features will not be seen unless significant erosion of the cover occurs.