Steephead valley

Such closed valleys may arise in limestone or karst landscapes, where a layer of permeable rock lies above an impermeable substrate such as marl.

[2] If the ponor cannot contain the high runoff during a flood event an intermittent flow may continue through the valley beyond the sink.

[3] They are created by a stream flowing within the permeable rock and eroding it from within, until the rock above collapses opening up a steep narrow valley which is then further eroded by the stream running across the impermeable valley floor.

[citation needed] At the head of the valley the stream emerges from the rock as a spring.

In North America, blind valleys (the preferred American term) are found in the Driftless Area and other karst regions.