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SINKHOLES IN ALABAMA
In Alabama,
the most common causes of land subsidence are the development of sinkholes
in areas underlain by soluble carbonate rocks or ground collapse above
abandoned mines. Many areas of the state, particularly north Alabama, are
underlain by carbonate rocks, such as limestone, that are susceptible to
dissolution and the formation of caves and sinkholes.
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Click the above map to see
details.
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Sinkhole Data and
Maps
To explore sinkholes in your area, refer to the
interactive map below. The points on
this map represent topographic depression features on historical
1:24,000-scale topographic maps. While most of the topographic depressions
are related to sinkholes, some may also be related to mine subsidence.
Because the topographic maps were published in the
1970s, more sinkholes may have developed since then. Please note that this
interactive map is for educational use only and is not meant for use for
site-specific evaluations. Click
here for sinkhole GIS data and metadata associated with the interactive map
below.
Not all web browsers or connection speeds support the below
interactive map. If you do not see the map below, click here.
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EXAMPLES OF KARST IN ALABAMA
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Newsome
Sinks area of Morgan
County on the Newsome
Sinks 1:24,000 quadrangle map overlain with 2006 aerial imagery.
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Largest Karst Topographic Area in Alabama
The topography of northern Alabama is dappled with sinkholes,
springs, and cave openings – all features of what is referred to as karst
topography. Of particular interest is the Newsome Sinks area in Morgan County. This topography is comprised
of coalescing sinkholes and represents the longest karst topographic
feature in the state – a little over 4 miles long! This area is underlain
by the Mississippian age Bangor Limestone.
Newsome Sinks area of Morgan County
on a 1:100,000 topographic map overlain with geology. Blue areas are Bangor
Limestone.
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The
Newsome Sinks area and much of northeastern Alabama is part of the
Tennessee-Alabama-Georgia karst area that cavers call TAG. Click
here to see some amazing TAG photos and read a National Geographic
article featuring this karst area.
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Largest Sinkhole in Alabama
The largest sinkhole in Alabama
developed near Calera in Shelby
County in December 1972
and has been called the “Golly Hole.” A local resident heard what sounded
like trees crashing during the night. The following day, hunters in the
area discovered a large sinkhole - about 325 feet long, 300 feet wide
(roughly a football field length across!), and 120 feet deep. This sinkhole
occurred during a drought when the water table was much lower than normal.
This particular area of Shelby County
has had a history of sinkhole development and is underlain by soft
limestones. Previous research indicates
hundreds of historical collapse features within a 16- square-mile area
(Warren and Wielchowsky, 1973). Most of these historical and recent
sinkholes are within the Dry
Valley which is
underlain with deeply weathered Cambrian dolomites of the Knox Group.
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The
“Golly Hole” in Shelby County as shown on aerial imagery (left), the
1:24,000 Alabaster topographic map (middle), and photo from the ground (photo by Tom Stone).
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To read more on the Golly Hole and its related geology,
see the below references:
LaMoreaux, P.E. and Warren, W.M., 1973, Sinkhole: Geotimes. v. 18,
no. 3, p. 15.
Warren, W.M. and Wielchowsky, C.C., 1973, Aerial remote
sensing of carbonate terranes in Shelby County, Alabama: Groundwater, v.
11, no. 6, p. 14-26.
To download geology shapefiles for the Alabaster Quadrangle
geologic map, click here.
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SINKHOLES NEAR YOU – WHAT YOU SHOULD DO
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Each year in Alabama,
a number of property owners find themselves facing sinkhole development on
their property – sometimes directly endangering
their homes or businesses. What should you do?
If Your Property is in a Sinkhole-Prone
Area
1. Examine the water drainage around your home to
insure water runoff or drips/leaks are not eroding areas around or under the
home and that water does not disappear into a hole near your property.
2. Look on your property for signs of subsidence where
the ground surface is depressed, wetter than the surrounding area, or with
lusher vegetation than the surrounding area. Look for any holes in the
ground that could indicate a small sinkhole.
3. Examine structures on the property and look for
signs that the ground may be subsiding underneath the structure such as:
leaning structures, angled door frames, cracks in the walls or foundation,
and depressed and/or cracked pavement surfaces. To see examples of damage
sinkholes can cause to structures, click here to go to the
Sinkhole.org photo gallery.
4. Contact your insurance company. Usually damage from
sinkholes is not covered by average homeowner's insurance unless
specifically asked for - if you live in a sinkhole prone area, it is a good
idea to ask about sinkhole coverage.
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Home affected by developing sinkhole in the Birmingham area.
If a Sinkhole Occurs on Your Property
1. Put up a barrier
surrounding the hole for safety and liability purposes.
2. Contact your property or
homeowner's insurance company.
3. Consider contacting a geological
or geotechnical engineering company to inquire if someone could come to
your property to assess the situation further. Contact information for
engineers can be found in your local phone directory. Please note that GSA
does not have the necessary engineering equipment to assess sinkhole growth
or subsurface voids.
4. If the sinkhole is large,
is in a residential neighborhood affecting public safety or public property
(streets/sidewalks/etc.) or appears related to city/county water/sewer
drainage, or the subsidence is affecting multiple homes, consider
contacting the city or county engineer's office, the Department of
Transportation, or the local emergency management agency.
Please note response capabilities may vary from county to county.
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LEGAL
ASPECTS OF SINKHOLES IN ALABAMA
Did you know that sinkholes are protected in Alabama? Because
sinkholes are a direct conduit to the groundwater, any contaminants dumped into
a sinkhole may end up in the groundwater. About 40% of public water
supplies in Alabama are from ground-water
sources and 27 south Alabama
counties receive all of their public water supplies from ground-water
sources. Since much of Alabama
gets their water from groundwater resources, it is important to protect the
groundwater quality, and therefore sinkholes too. The below information
lists some of the regulations related to karst, caves, and sinkholes in the
state of Alabama.
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Specifically,
the Alabama Cave Protection Law of 1988 states that “It shall be unlawful and constitute a misdemeanor for any person,
organization, firm, corporation, including any officer, employee or agent
of any town or municipality to risk the pollution of the underground
water resources of the state by storing, dumping, disposing, or otherwise
placing in caves, sinkholes or natural wells: chemicals, refuse, dead
animals, garbage or other materials which are potentially injurious or
hazardous to the quality of the aquifer, water and/or water table.” Alabama Cave Protection Law (1988), (Acts
1988, No. 88-582, p. 909, §4.), Section 9-19-4. Click
here to go to the Alabama Legislative Information System Online to
read the full text.
Additional
regulations from the Alabama State Board of Health’s Division of
Community Environmental Protection relate to onsite sewage treatment and
disposal with respect to sinkholes and planning:
Administrative
Code Chapter 420-3-1.
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