What is a Sinkhole?
Sinkhole
A sinkhole is a hole in the ground that forms when water dissolves surface rock. Often,
this surface rock is limestone, which is easily eroded, or worn away, by the movement of water.
In a landscape where limestone sits underneath the soil, water from rainfall collects in
cracks in the stone. These cracks are called joints. Slowly, as the limestone dissolves and is
carried away, the joints widen until the ground above them becomes unstable and collapses.
The collapse often happens very suddenly and without very much warning. Water collects in
these collapsed sections, forming sinkholes.
Sinkholes vary from shallow holes about 1 meter (3 feet) deep, to pits more than 50
meters (165 feet) deep. Water can drain through a sinkhole into an underground channel or a
cave. When mud or debris plugs one of these underground caves, it fills with water to become a
lake or a pond.
Sinkholes occur naturally, especially where there is abundant rainfall, and the rock
beneath the surface soil is limestone. People can also create sinkholes when building roads,
aquifers, or other types of construction. Altering land in these ways can weaken the underlying
rock and make it more susceptible to sinkholes. Sinkholes can open up in the middle of busy
streets or in neighborhoods, especially during heavy rainfall.
The land surrounding the Dead Sea in the Middle East is prone to sinkholes because of
the prevalence of rock salt, which is easily dissolved by water. Tourists who are unaware of
sinkholes and even scientists studying sinkholes have been injured by falling into them.