Why are fossils usually flat?
Show answer & explanation
Answer: Sediment layers compress them
Sediment layers compress them ✓ — Correct! When organisms die and get buried in sediment (mud, sand), more and more layers pile on top over millions of years. The immense weight of overlying rock compresses everything, flattening fossils. This is especially true for soft-bodied organisms and plants. Some 3D fossils exist in special conditions, but most are compressed!
Organisms were naturally flat — Wrong. Many fossilized organisms were 3D (fish, shells, bones). They become flat from millions of years of sediment weight compressing them.
Heat melts and flattens them — Wrong. Fossils form in sedimentary rock through burial and mineral replacement, not heat. Metamorphic heat usually destroys fossils.
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