Solved cryptogram
A limestone cave was not hollowed out by a river. The rock was dissolved by slightly acid water.
Earth Science Facts, sourced to U.S. National Park Service.
Or go to the puzzle’s own page first.
What it means
Rain picks up carbon dioxide from the air and from soil and becomes a weak carbonic acid, and limestone is soluble in it. Water seeps along joints and bedding planes, widening them over hundreds of thousands of years until a person could walk through. The landscape above such rock is called karst, and it comes with sinkholes, disappearing streams and springs, because the drainage has gone underground.
The claim comes from U.S. National Park Service.
- SourceU.S. National Park Service
- CollectionEarth Science Facts
- Difficultymedium
- Length77 letters, 20 unique
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