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🦴 How do fossils form?

Rapid burial, mineral fill or molds, and layered rock turn rare remains into a deep-time archive.

lessons

~10 min

to learn

🔬 Science

subject

Adults

level

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What you’ll learn

Burial before decay winsExplain why rapid burial and hard parts dominate who becomes a fossil.Most remains vanish. Quick cover under sediment and tough tissues raise the odds that geology can archive something of the organism.
Minerals rewrite the remainsDistinguish permineralization, molds/casts, and exceptional preservation modes.Minerals fill pores, copy shapes after dissolution, or trap specimens in amber and similar special settings — substance and form can part ways.
Reading rock as a timelineConnect fossils to stratigraphy, index markers, and trace evidence of behavior.Layer order and dating methods place fossils in time; tracks and burrows record behavior even without a body.

Questions this course answers

Put these stages of a typical hard-part fossil path in order

Fossilization usually needs burial before total destruction, then long mineral and rock processes, then exposure so we can find the specimen.

What is permineralization?

Groundwater carries dissolved minerals into empty spaces of hard tissues; crystals form there and can lock in fine anatomical detail.

Why can a fossil be useful even when the original shell or bone has completely dissolved?

A mold or cast records geometry after the original material is gone; traces record activity. Position in rock layers still places the organism in time.

Grounded in trusted sources

Smithsonian National Museum of Natural History — fossilization and taphonomy education pages
U.S. Geological Survey — sedimentary rocks, stratigraphy, and geologic time resources
University paleontology / natural history museum primers on permineralization, molds, casts, and amber
British Geological Survey / Open University-style explainers on the fossil record and bias

Every Wunder lesson is built from real, reputable sources — never invented.

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