Solved cryptogram
Fossils turn up in sedimentary rock, because the heat that makes the other kinds destroys them.
Earth Science Facts, sourced to U.S. Geological Survey.
Solve it yourself
This fact is a cryptogram here: 78 letters over 19 different ones, graded medium.
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What it means
Sediment settles gently, in layers, at temperatures a shell or a bone can survive. Igneous rock arrives as a melt, and metamorphic rock is recooked hard enough to rearrange its own minerals, so neither preserves a body. That is a strong constraint on where anyone can look for the history of life. The fossil record is not a record of the past in general; it is a record of the places where mud was piling up quietly.
The claim comes from U.S. Geological Survey.
- SourceU.S. Geological Survey
- CollectionEarth Science Facts
- Difficultymedium
- Length78 letters, 19 of them different
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