Question
Explain the evolution of valley sinks or uvalas.
Solution
i. A sink hole is on opening more or less circular at the top and funnel-shaped towards the bottom with sizes varying in area from a few sq.m to a hectare and with depth from a less than half a metre to thirty metres or more.
ii. Quite often the surface run-off simply goes down swallow and sink holes and flow as underground streams and re-emerge at a distance downstream through a cave opening.
iii. A doline is a collapsed sink. When sinkholes and dolines join together because of slumping of materials along their margins or due to roof collapse of caves, long narrow to wide trenches called valley sinks or uvalas form.
ii. Quite often the surface run-off simply goes down swallow and sink holes and flow as underground streams and re-emerge at a distance downstream through a cave opening.
iii. A doline is a collapsed sink. When sinkholes and dolines join together because of slumping of materials along their margins or due to roof collapse of caves, long narrow to wide trenches called valley sinks or uvalas form.
