Surface Karst Features
Dolines are closed depressions in karst areas, which are usually circular in outline. Dolines may be produced by solution of rock close to the surface, or by the roof of a cave collapsing. Solution dolines tend to have a smooth funnel shape, while collapse dolines often have cliffed sides. Streams often sink underground through dolines.
In karst areas, most of the drainage is underground. As they flow onto the limestone, streams sink underground and travel through caves. In dry valleys, the surface streams flow in times of heavy rain only, when the underground drainage is unable to cope with the flow. Dry valleys often contain large boulders, but little fine sediment as their streams only flow during floods, when there is too much energy to deposit mud and silt.
Vertical joints and bedding planes in limestone can be widened by solution to form deep elongated slots. These slots are called grikes.
Falling rain is able to disolve limestone, because it contains carbon dioxide from the atmosphere. Rainwater runs down limestone and sculptures it, each run of water dissolving a groove or solution flute into the limestone. This type of fluting, consisting of parallel vertical grooves, is known by its German name, Rillenkarren.
A streamsink is the point at which a surface stream disappears underground.
The resurgence is the point of reappearance from underground, of a stream, which has a course on the surface higher up.
A blind valley is one that is closed abruptly, at its lower end, by a cliff or slope facing up the valley. It may have a perennial or intermittent stream, which sinks at its lower end, or it may be a dry valley.
A steephead is a steep-sided valley in karst, generally short, ending abruptly upstream, where a stream emerges (or emerged in the past).