Short answer
A sinkhole is a depression at the ground surface without natural external surface drainage; a cave is an underground space or passage system. They can connect: a sinkhole may drain into cave passages, and loss of support above an underground space can cause surface collapse. They are not interchangeable names for the same feature. 1 2
On this page
At a glance
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| Attribute | Sinkhole | Cave |
|---|---|---|
| Feature being named | Surface depression | Underground space or passages |
| Water relationship | Typically drains underground | May carry streams or be water-filled |
| Connection between them | Can feed passages below | Can receive sinkhole drainage |
| Does the name require sudden collapse? | No | No |
These distinctions follow the USGS sinkhole definition and NPS description of solution caves. 1 2
What each thing is
The defining sinkhole feature is a depression with no natural surface outlet, rather than a particular dramatic appearance. For caves, distinguish the general category from solution caves: NPS identifies several cave types, with solution caves developing through dissolution and erosion along weaknesses in rock. 1 2
Key differences
The terms describe different parts of the landscape, not simply different sizes of hole. Sinkhole emphasizes surface shape and drainage; cave emphasizes underground space. Dissolution can create underground cavities before the ground above loses support, so cave development and surface collapse need not happen together. 1 2
How to tell them apart
Ask what is being identified: a surface depression without an external surface outlet, or an underground chamber or passage? That is a useful naming rule, not a field diagnosis. A depression alone does not establish its cause; USGS also mentions leaking pipes and settling buried materials. 1
Where they overlap
In karst, sinkholes and solution caves can function as connected parts of a drainage system. Water entering through sinkholes can feed passages below, while water transports sediment and dissolved rock downward. NPS groups caves, sinkholes, and sinking streams among the features of karst landscapes. 2
Edge cases
A sinkhole draining directly into cave passages can be described using both terms: one names the surface depression, the other the underground passages. Conversely, collapse inside a cave does not necessarily identify a surface sinkhole; NPS describes internal rock falls that block passages and redirect cave-forming water. 2
Why the distinction exists
Separating the terms preserves the difference between a surface drainage feature and the underground space associated with it. It also clarifies the collapse mechanism: USGS describes underground spaces growing while the surface remains intact, followed by possible collapse when support becomes insufficient. 1
Common misconceptions
A sinkhole need not begin as a sudden collapse: NPS also describes enlargement through downward removal of sediment and dissolved rock. Nor is every cave a dry, walkable tunnel; some solution caves are water-filled. Finally, solution cave is only one cave category, even though it is the most common. 2
Examples
Two hypothetical applications illustrate the distinction. First, rainfall collects in a closed depression and drains into passages below: call the depression a sinkhole and the passages a cave. Second, an underground stream enlarges a limestone passage while the surface remains intact: the passage is a cave, without establishing a surface sinkhole. 1 2