Do You Live in Sinkhole Territory?
common where the rock below the land surface is limestone, carbonate
rock, salt beds, or rocks that can naturally be dissolved by ground
water circulating through them. As the rock dissolves, spaces and
caverns develop underground. Sinkholes are dramatic because the
land usually stays intact for a while until the underground spaces
just get too big. If there is not enough support for the land above
the spaces then a sudden collapse of the land surface can occur.
These collapses can be small, as this picture shows, or they can
be huge and can occur where a house or road is on top.
The most damage
from sinkholes tends to occur in Florida, Texas, Alabama, Missouri,
Kentucky, Tennessee, and Pennsylvania. The picture to the left shows
a sinkhole that quickly opened up in Florida, apparently eating
a swimming pool, some roadway, and buildings.
to collapse sinkholes
The map below
shows areas of the United States where certain rock types that are
susceptible to dissolution in water occur. In these areas the formation
of underground cavities can form and catastrophic sinkholes can
happen. These rock types are evaporites (salt, gypsum, and anhydrite)
and carbonates (limestone and dolomite). Evaporite rocks underlie
about 35 to 40 percent of the United States, though in many areas
they are buried at great depths.
Map of the United States showing areas where rock that are prone
to dissolution and sinkholes are prevalent.
can be human-induced
have been correlated to land-use practices, especially from ground-water
pumping and from construction and development practices. Sinkholes
can also form when natural water-drainage patterns are changed and
new water-diversion systems are developed. Some sinkholes form when
the land surface is changed, such as when industrial and runoff-storage
ponds are created. The substantial weight of the new material can
trigger an underground collapse of supporting material, thus causing
sediments that cover buried cavities in the aquifer systems are
delicately balanced by ground-water fluid pressure. The water below
ground is actually helping to keep the surface soil in place. Groundwater
pumping for urban water supply and for irrigation can produce new
sinkholes In sinkhole-prone areas. If pumping results in a lowering
of ground-water levels, then underground structural failure, and
thus, sinkholes, can occur.