Fossilisation: Why Sediment, Minerals and Luck All Matter · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

How a fossil forms

Science · Dinosaurs & Paleontology · ages 7-9
Name ______________________   Date ____________

  1. What do we call the mud, sand, and dirt that can bury a dead animal?

    • sediment
    • minerals
    • fossil

  2. What is the very first step in a fossil forming?

    • The animal or plant dies
    • Minerals replace the bones
    • The sediment turns to rock

  3. Most animals and plants that die become fossils.

    Circle one:   True   False

  4. Which word means the hard material that slowly takes the place of bone?

    • minerals
    • sediment
    • fossil

  5. A fish dies and sinks to the muddy bottom of a lake. More mud piles on top of it for thousands of years. What is slowly happening to the fish's bones deep under the lake floor?

    • Its bones are slowly turning into stone
    • Its bones are drying out and blowing away
    • Its body is slowly coming back to life

  6. Why does it take millions of years to make a fossil, instead of just a few weeks?

    • Because minerals replace the remains only a little at a time
    • Because the animal has to die many times
    • Because sediment falls all in a single day

  7. Theo says, 'A fossil forms when sediment turns into minerals.' What did Theo mix up?

    • It is the remains that minerals replace, while the sediment around them turns to rock
    • Nothing, Theo is completely right
    • Sediment and minerals are actually the same thing

  8. A bird dies on a sunny rock and nothing covers it for weeks. Will it likely become a fossil?

    • No, it will rot away before sediment can bury it
    • Yes, sunlight turns bones into fossils
    • Yes, all dead animals become fossils eventually
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Answer key

For grown-ups. Fold this page away before handing over the rest.

How a fossil forms W1-mt_iycQEai3dK-s1

  1. sediment · Sediment is the mud, sand, and dirt that settles in layers and can cover remains.
  2. The animal or plant dies · Before anything else can happen, the plant or animal has to die first.
  3. False · Almost all living things rot away or get eaten before they can be buried, so fossils are rare.
  4. minerals · Minerals are the hard materials that replace the bone, turning it to stone.
  5. Its bones are slowly turning into stone · Once the fish is buried, its remains slowly change into stone over a very long time. That stony copy is the fossil.
  6. Because minerals replace the remains only a little at a time · The minerals build up so slowly that the whole change takes a very long time.
  7. It is the remains that minerals replace, while the sediment around them turns to rock · Minerals replace the animal's remains. The sediment around it is what turns into rock.
  8. No, it will rot away before sediment can bury it · Without a fast burial in sediment, the body rots away and no fossil can form.
Worksheet · LightMySky