Is this address in sinkhole country?
Is this address in sinkhole country — and what has already collapsed nearby?
A fifth of the United States sits on rock that dissolves. The USGS mapped it; Florida logs every reported collapse; our satellite archive measures whether the ground has already moved. Enter an address and we read all three, free: the rock under the point, the recorded collapses within 1 km where a state keeps that record, and the measured ground motion. Honest limits first: the karst map is national-scale, so it describes the rock under the point rather than the lot; only Florida publishes an incident register; and nobody can predict a sinkhole — this reports the setting, the record and the movement, which is what a geologist would start from.
What the check reads
The rock under the point
USGS national karst map: carbonate or evaporite rock, at the surface or under a shallow cover — or pseudokarst, or nothing soluble at all
Recorded collapses
every Florida Geological Survey subsidence incident within 1 km: date, distance, size, and whether it was verified as a true sinkhole
Measured ground motion
NASA OPERA InSAR at the nearest measured cell: is this ground already sinking, and how fast
One verdict, with its reasons
Low, Moderate or Significant, each stated with the evidence behind it and the limits of that evidence
The check is free and stays free. For a purchase, the $19 HomeGround report puts the sinkhole setting beside flood, wildfire, earthquake, coastal and environmental records for the same address, with a PDF.
What causes sinkholes in the United States?
Soluble rock, almost always. About a fifth of the country sits on carbonate rock — limestone and dolomite — or evaporites such as gypsum and salt, and where groundwater has had time to dissolve cavities in it, the ground above can subside slowly or collapse suddenly. Florida is the textbook case: limestone under a shallow cover of sand and clay, which ravels into the cavities below without warning — the "cover-collapse" sinkhole. Texas, Tennessee, Kentucky, Alabama, Missouri and Pennsylvania are the other classic states. Lava tubes in the Pacific Northwest and Hawaii, piping in the loose sediments of the West, and thawing permafrost in Alaska produce holes by other mechanisms — pseudokarst — and the check names them as such. Burst water mains, old fill and abandoned mine workings can open a hole on any geology and are not on any national map.
Can you predict a sinkhole at an address?
No. Nobody can, and a service that implies otherwise is selling reassurance rather than information. What can be known is the setting — is the rock under the point soluble, and is it exposed or under a shallow cover — the record — has the ground here or next door already collapsed — and the movement — has the surface been measured sinking. This check reads all three from public data and says which one it is looking at. The USGS karst map is a national-scale compilation, so it tells you what rock is under the point, not what is under the lot; the Florida incident register locates reports to the parcel or, for older ones, to the square-mile section; and the ground-motion reading is at the nearest measured radar cell, not a survey of your foundation.
Was the Nicolas Cage driveway collapse a sinkhole?
Not in the geological sense. The Malibu collapse that made headlines in September 2026 was reported by the Associated Press as coastal erosion after the remnants of Tropical Storm Marie, with a gas leak in the mix — a cliff-edge failure, not dissolution of soluble rock. Most "sinkhole" headlines are like this: a washed-out water main, a collapsed storm drain, cliff retreat. A true sinkhole needs soluble rock beneath it, which is why the check starts by asking what rock is actually under the point rather than treating every hole in the news as the same thing.
Why does the check know about collapses in Florida and not in my state?
Because Florida is the only state that keeps an open, address-level register of reported collapses and publishes it live. The Florida Geological Survey’s Subsidence Incident Report database holds more than four thousand reports since the 1950s, each with a date, a location, whether it was verified as a true sinkhole, and often its size. We read it live for every Florida address, within 1 km. Other karst states keep sinkhole inventories at very different levels — Kentucky and Tennessee map sinkhole depressions from elevation data, Pennsylvania and Missouri hold research databases — and none is an incident register you can query by address. Where that record does not exist we say so, rather than pretending an absence of data is an absence of history.
My result says Significant. What should I do?
Read what it is rating first: soluble rock is at or near the surface here, or under a shallow cover — the setting in which sinkholes form. It is a common setting, and the overwhelming majority of homes on it never see a hole. What changes is the questions worth asking. For a purchase in Florida, the seller must disclose known sinkhole activity and past insurance claims, and a sinkhole inspection by a licensed geologist or engineer is a routine and reasonable condition; check whether the recorded incidents on your result are on the property or across the street. For a home you own: watch for the signs that precede a collapse — a new depression in the yard or driveway, cracks that open in a stair-step pattern, doors and windows that start to bind, fence posts or trees that tilt, water pooling where it did not — and if the measured ground motion on your result is already negative, take those signs seriously, faster. The full HomeGround report puts the karst setting beside flood, wildfire, earthquake and the measured motion in one document.
Which areas are covered?
The karst setting covers all fifty states plus Puerto Rico and the US Virgin Islands, from the USGS "Karst in the United States" compilation (Weary & Doctor, 2014). The recorded-collapse layer is Florida only. The ground-motion layer is NASA’s OPERA InSAR archive, which measures most of the country’s built-up ground; where no measurement lies close enough to the point, the result says so rather than guessing.
Sources: USGS Open-File Report 2014-1156, “Karst in the United States” (Weary & Doctor; public domain); Florida Department of Environmental Protection / Florida Geological Survey Subsidence Incident Reports (read live; the FGS asks users to contact it before relying on the data for decisions); NASA OPERA DISP-S1 InSAR. A screening from public data at national scale, not a ground investigation and not a prediction. Burst mains, old fill and mine workings can open a hole on any geology and are not mapped. For any purchase or structural decision, consult a licensed geologist or engineer.
Novarly Parcel · official public data, read properly · parcel.novarly.com