põhjendadakoobe

Põhjendatud koobas is a type of explained karst window, specifically a type of doline that has been enlarged by water erosion and sediment collapse. These features are commonly found in areas of soluble bedrock, typically limestone, dolomite, or gypseous rocks.

Põhjendatud koobas are characterized by a large, open depression with steep walls and a flat or rounded floor. They can range in size from small, shallow depressions to large, deep cavities, sometimes extending underground through collapsed underground passages and fissures. The formation of these features is attributed to a combination of water erosion, the collapse of overlying rocks, and the process of karstification.

Within põhjendatud koobas, karstification is the dominant process driving the dissolution of the bedrock. This dissolution process is accelerated when water percolating through the bedrock becomes slightly acidic, reacting with and dissolving soluble minerals in the rock. As the rock is progressively dissolved, the bedrock becomes weakened, prone to collapse. The introduction of groundwater can help quicken the rate of dissolution and accelerate the frailty of the rocks.

Farming, mining, and other human activities can accelerate the effect of karst processes. Subsidence and land subsidence caused by localised mass collapse into extensive underground passageways can very well render centralised settlements depleted and change the local ecosystem extensively.