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A devastating sinkhole occurred in Florida on February 28, 2013, raising questions and concerns about this incredible phenomenon. Around 20% of the U.S. lies in areas susceptible to sinkhole events, highlighting the need for research and to be informed about this hazard.
A devastating sinkhole occurred in Florida on February 28, 2013, raising questions and concerns about this incredible phenomenon. Around 20% of the U.S. lies in areas susceptible to sinkhole events, highlighting the need for research and to be informed about this hazard.
What is a Sinkhole?
Geologically, a sinkhole is a depression in the
ground that has no natural external surface drainage. Basically this means
that when it rains, all of the water stays inside the sinkhole and typically
drains into the subsurface.
Sinkholes are most common in what geologists call, “karst terrain.”
What’s that? These are regions where the type of rock below the land
surface can naturally be dissolved by groundwater circulating through them.
Soluble rocks include salt beds and domes, gypsum, and limestone and other carbonate rock. Florida, for instance, is an area largely underlain by limestone and is highly susceptible to sinkholes.
Soluble rocks include salt beds and domes, gypsum, and limestone and other carbonate rock. Florida, for instance, is an area largely underlain by limestone and is highly susceptible to sinkholes.
When water from rainfall moves down through the soil, these types of
rock begin to dissolve and spaces and caverns develop underground. Sinkholes
are dramatic because the land usually stays intact for a period of time 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.
Keep in
mind though that while collapses are more frequent after intense rainstorms,
there is some evidence that droughts play a role as well. Areas where water
levels have lowered suddenly are more prone to collapse formation.
Areas
Most Susceptible
About 20% of our country is underlain by “karst terrain” and is susceptible to a sinkhole event. The most damage from sinkholes
tends to occur in Florida, Texas, Alabama, Missouri, Kentucky, Tennessee, and
Pennsylvania.
Different
Types and Various Severities
Sinkholes can be characterized into two types.
First,
there are cover-collapse sinkholes, which can develop abruptly (over a period
of hours) and cause catastrophic damages.
Secondly,
there are cover-subsidence sinkholes, which form slowly over time with the
ground gradually subsiding or deflating. These types of events can be less
noticeable and go undetected for long periods.
Sinkhole
collapses can range in size and severity. Sinkholes can vary from a few feet to
hundreds of acres and from less than one to more than 100 feet deep. Sinkholes
can have dramatic effects, especially in urban settings. They can contaminate
water resources and have been seen to swallow up swimming pools, parts of roadways,
and even buildings.
Is There
a Sinkhole on Your Property?
This is a difficult question, and unfortunately
there isn’t a very efficient system to determine this quite yet. It is
recommended that people constantly observe their property for things such as
small holes in the ground or cracks formed in a structure’s foundation. People
can also check to see if they live in areas underlain by soluble rock, and they
can do so by checking with county offices, local or state geological surveys,
or the USGS.
Even
Humans Cause Sinkholes
Houston Water Pump with Mazaki Automatic Pump Controller |
While sinkhole collapses are frequent in karst
areas, there are a variety of other circumstances that can lead to such events.
Many sinkholes form from human activity. Collapses can occur above old mines,
from leaky faucets, when sewers give way, or due to groundwater pumping and
construction.
Think
about all the changes that occur when water-drainage patterns are altered and
new systems are developed. And when industrial and runoff-storage ponds are
created, the resulting substantial weight of the new material can trigger an
underground collapse of supporting material.
Ballast-type Pressure Tanks |
Groundwater
pumping for urban water supply and for irrigation can produce new sinkholes. If
pumping results in a lowering of groundwater levels, then underground
structures could fail and thus sinkholes can occur.
RELATED POSTS:
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MGB discovers 88 sinkholes in
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What is groundwater?
http://puricare.blogspot.com/2016/06/groundwater-there-is-immense-amount-of.html
source: www2.usgs.gov
PURICARE
INDUSTRIAL
ENTERPRISES
Water
Treatment
Systems
Ultraviolet Bactericidal System with Cartridge Pre-Filters |
source: www2.usgs.gov
JESSICA
ROBERTSON (JROBERTSON@USGS.GOV) AND RANDALL ORNDORFF (RORNDORF@USGS.GOV)
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