Parcels · Hazard layers · Sinkholes · October 16, 2026

Sinkhole Map: How to Check a Property for Sinkholes

How to use a sinkhole map to check a parcel: state sinkhole and karst layers, Florida incident reports, terrain clues, and what the map can't prove.

A sinkhole map shows where the ground has collapsed or sagged in the past, or where the rock below is the kind that can dissolve and leave voids. Buyers pull one up before making an offer on land in Florida, central Kentucky, south-central Pennsylvania or the Missouri Ozarks, and owners use one when a low spot or a crack makes them wonder what is under the lawn. No single national map answers the question for one lot, though. The useful maps are mostly kept by state geological surveys, and each one shows something a little different. This guide explains the main kinds, how to check a parcel, how to read the results and what to do if the map raises a flag.

What a sinkhole map can show

• Karst maps. Sinkholes form where soluble rock such as limestone, dolomite or gypsum lies under the surface, terrain geologists call karst. The U.S. Geological Survey’s Karst in the United States compilation maps rock with karst potential across the country and estimates that about 18 percent of U.S. land is underlain by soluble rock. The USGS notes that these maps do not rate sinkhole collapse risk; they show where it is geologically possible.
• Sinkhole inventories. Some states map individual sinkholes and closed depressions, usually from topographic maps, aerial photos or elevation data, sometimes checked in the field.
• Incident reports. Florida keeps a statewide database of reported ground subsidence. These are reports, not confirmed sinkholes.
• Depression density maps. The USGS has also published a nationwide dataset of closed depressions in karst areas, drawn from elevation data, which highlights regional sinkhole hot spots.

Where to find a sinkhole map for your state

• Florida. The Florida Geological Survey’s Subsidence Incident Reports can be viewed on the state DEP’s Map Direct viewer or downloaded from its GIS open data portal. The records come from voluntary reports by residents, local governments and the state transportation department, and the survey says most have not been field-checked and the cause is often unknown.
• Pennsylvania. The state geological survey shows mapped sinkholes and surface depressions under a karst features layer in its PaGEODE web map. The inventory is incomplete and detailed mostly for counties in the south-central and southeastern part of the state.
• Kentucky. The Kentucky Geological Survey offers statewide sinkhole outlines digitized from topographic maps, plus a karst occurrence map and county downloads.
• Missouri. The state Department of Natural Resources publishes known and probable sinkhole locations as a GIS layer.
• Other states. Tennessee, Alabama, Texas, Virginia, Indiana and other states with karst have their own geological surveys. Search the survey’s site for “karst” or “sinkholes,” and check whether the county GIS viewer has a karst or geologic hazard layer.

How to check a property on a sinkhole map

1. Locate the parcel. Pull it up in the county’s parcel viewer and write down its parcel number; see how to find a parcel number by address. Our land map links to county viewers.
2. Check the bedrock first. Open the karst map or the state geologic map. If the parcel is not over soluble rock, natural sinkholes are unlikely, though settling from other causes is still possible.
3. Look for mapped sinkholes and reports. Turn on the state inventory or incident layer and zoom to the parcel and the land around it. Note how close the nearest features are and whether they cluster.
4. Read the terrain. On a topographic map of the property, closed depressions are drawn as contour loops with short tick marks pointing inward. A lidar hillshade shows them even more clearly; see what lidar elevation data is.
5. Compare old aerial photos. Round ponds, wet spots or rings of trees that come and go between years can hint at depressions. Our guide to finding historic aerial photos shows where to look.
6. Read the soil survey. In karst areas, soil map unit descriptions sometimes mention sinkholes or depressions. See what a soil survey is.

How to read what you find

• A dot is not proof. A reported incident may be a true sinkhole, a broken pipe, a rotting buried stump or soil that was never compacted after digging. Florida’s survey lists all of these as things that can mimic sinkhole activity.
• No dot is not a clean bill. Inventories cover only what someone mapped or reported. Features in fields and woods often go unrecorded, and reports cluster where people live and drive.
• Points can be off. Locations in report databases are often approximate, so do not read a point as sitting on a specific house.
• Karst areas are big. Being over soluble rock puts a parcel in the area where sinkholes can form. Only a small part of that area has serious collapse hazard.

Why it matters when buying land

• Insurance. In Florida, property insurers must cover catastrophic ground cover collapse, a narrow event that ends with the home condemned. Broader sinkhole loss coverage is optional, offered for an added premium, and the insurer may inspect the property before selling it. Ask about coverage before you close.
• Disclosure. Some state disclosure forms ask sellers about known sinkholes, settling or past repairs. Ask the seller directly and read the form closely.
• Building and septic. Karst can affect where a house, a pond or a septic system can safely go. Check septic records and ask the county about local rules.
• Water. Karst ground can carry surface water quickly into the aquifer, so a well on karst land deserves a careful look; see how to find well records.

Signs on the ground to look for

• Round or oval depressions, or a dip in the lawn that keeps growing.
• New cracks in a foundation, slab, driveway or pool deck.
• Doors and windows that start to stick or no longer close.
• Fence posts, trees or utility poles that begin to lean.
• Water that suddenly ponds where it used to drain, or a pond that drains away.

Many of these have ordinary causes, such as clay soils that shrink and swell or a leaking pipe, so treat them as reasons to look closer, not as a diagnosis.

What to do if the map raises a flag

1. Ask the seller and neighbors what they know, and look up any past insurance claims or repairs the seller will share.
2. Call the state geological survey; staff can often explain what a mapped feature is.
3. Hire a geotechnical engineer or professional geologist to evaluate the site. An investigation may include soil borings or ground-imaging surveys.
4. If a hole opens suddenly, keep people and pets away, mark it off and contact local authorities. Do not try to fill an active hole yourself before it is assessed.

What a sinkhole map cannot tell you

• Whether a hole will open under a given house, or when.
• Whether a past report was ever confirmed or repaired.
• Where the property lines are. For that, see how to read a property survey.

A sinkhole check fits well with the other hazard layers on the same viewer: the flood zone by address, a wildfire risk map and wetlands.

Questions people ask

Related guides

• Topographic map of my property
• What is lidar elevation data?
• How to find historic aerial photos
• Wildfire risk map: check a property’s fire hazard zone
• How to find a flood zone by address