Fossil Types Quiz: Molds, Casts, and More

1. Which of the following is the first step in forming a mold fossil?

An organism is buried in sediment

An organism turns into gold

An organism runs away

An organism dissolves immediately

If a fossil is to form, then the remains must be protected from scavengers and weather. If sediment layers pile up over an organism, then it is preserved for later processes. Therefore, burial is the essential first step.

Explanation

If a fossil is to form, then the remains must be protected from scavengers and weather. If sediment layers pile up over an organism, then it is preserved for later processes. Therefore, burial is the essential first step.

2. What happens to the original shell or bone to create a mold fossil?

It grows larger

It dissolves or decays away

It turns into a living animal

It stays exactly the same forever

If sediment hardens around an object, then the object's shape is captured. If the object later dissolves due to water or decay, then only the empty space remains. Therefore, the removal of the original material creates the mold.

Explanation

If sediment hardens around an object, then the object's shape is captured. If the object later dissolves due to water or decay, then only the empty space remains. Therefore, the removal of the original material creates the mold.

3. Which word best describes a mold fossil?

A 3D statue

An empty imprint or cavity

A footprint in mud

A piece of petrified wood

If a mold is formed by an object dissolving out of hardened rock, then the result is a hollow space. If the space matches the outside of the original object, then it is an imprint or cavity.

Explanation

If a mold is formed by an object dissolving out of hardened rock, then the result is a hollow space. If the space matches the outside of the original object, then it is an imprint or cavity.

4. A cast fossil is a 3D model that looks like the original organism.

True

False

If minerals and sediment fill up a hollow mold, then they take on the shape of that space. If the space was shaped like the original shell, then the hardened filler becomes a 3D replica. Therefore, the statement is true.

Explanation

If minerals and sediment fill up a hollow mold, then they take on the shape of that space. If the space was shaped like the original shell, then the hardened filler becomes a 3D replica. Therefore, the statement is true.

5. What is required to turn a mold into a cast?

Sunlight

Magic

Minerals or sediment filling the mold

Wind blowing over the rock

If a mold is just an empty hole, then it needs material to create a solid object. If water carries minerals into that hole and they harden, then a cast is formed. Therefore, filling the mold is the necessary step.

Explanation

If a mold is just an empty hole, then it needs material to create a solid object. If water carries minerals into that hole and they harden, then a cast is formed. Therefore, filling the mold is the necessary step.

6. A fossil that shows the "negative" space or an empty impression of an organism is called a ______.

If an organism leaves a hollow shape in a rock after it decays, then it is not a solid replica. If this hollow shape acts as a container for future minerals, then it is defined scientifically as a mold.

Explanation

If an organism leaves a hollow shape in a rock after it decays, then it is not a solid replica. If this hollow shape acts as a container for future minerals, then it is defined scientifically as a mold.

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7. If you press a seashell into playdough and then remove the shell, the hole left in the playdough represents which type of fossil?

Cast

Mold

Amber

Trace

If the playdough records the shape of the shell, then it is a record of the exterior. If the shell is removed leaving only the impression behind, then it matches the definition of a mold.

Explanation

If the playdough records the shape of the shell, then it is a record of the exterior. If the shell is removed leaving only the impression behind, then it matches the definition of a mold.

8. If you fill a seashell-shaped hole in playdough with plaster and let it harden, the hardened plaster represents which type of fossil?

Mold

Cast

Resin

Carbon film

If the hole is the mold, then the material used to fill it becomes the opposite. If the hardened plaster takes the physical form of the original shell, then it is a cast.

Explanation

If the hole is the mold, then the material used to fill it becomes the opposite. If the hardened plaster takes the physical form of the original shell, then it is a cast.

9. Molds and casts are usually found in igneous rock formed from lava.

True

False

If igneous rock forms from hot molten lava, then organic matter would be destroyed by the heat. If fossils require gentle burial to preserve shapes, then they must form in sedimentary rock. Therefore, the statement is false.

Explanation

If igneous rock forms from hot molten lava, then organic matter would be destroyed by the heat. If fossils require gentle burial to preserve shapes, then they must form in sedimentary rock. Therefore, the statement is false.

10. Why are mold and cast fossils important to scientists?

They show what the inside of the animal looked like

They show the external shape and surface details

They tell us what the animal's favorite food was

They show the animal's exact color

If a mold is formed by the outside of a shell or bone pressing into mud, then it captures textures. If the cast replicates that shape, then scientists can see the size and surface features of the organism.

Explanation

If a mold is formed by the outside of a shell or bone pressing into mud, then it captures textures. If the cast replicates that shape, then scientists can see the size and surface features of the organism.

11. Which of the following is NOT a characteristic of a cast fossil?

It is a solid object

It fills a mold

It is a hollow space

It looks like the original organism

If a cast is formed by filling a hole, then it must be a solid representation. If it is solid, then it cannot be a hollow space. Therefore, being a hollow space is the incorrect characteristic.

Explanation

If a cast is formed by filling a hole, then it must be a solid representation. If it is solid, then it cannot be a hollow space. Therefore, being a hollow space is the incorrect characteristic.

12. The minerals that form a cast are usually carried into the mold by ______.

If minerals are solid, then they need a way to travel into a tiny underground cavity. If water flows through rock layers, then it can carry dissolved minerals. Therefore, water is the primary transport mechanism.

Explanation

If minerals are solid, then they need a way to travel into a tiny underground cavity. If water flows through rock layers, then it can carry dissolved minerals. Therefore, water is the primary transport mechanism.

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13. Which of the following can become a mold fossil?

Hard shells

Bones

Soft leaves

Sunlight

If an object has a distinct shape and can be buried in sediment, then it can potentially leave an imprint. If shells, bones, and leaves have physical forms, then they can create molds. If sunlight has no mass, then it cannot.

Explanation

If an object has a distinct shape and can be buried in sediment, then it can potentially leave an imprint. If shells, bones, and leaves have physical forms, then they can create molds. If sunlight has no mass, then it cannot.

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14. What happens to the sediment over millions of years to help form a fossil?

It turns into water

It turns into hard rock

It disappears completely

It turns into soft sand

If layers of sediment pile up, then the weight creates high pressure. If pressure and time act on the layers, then they undergo lithification. Therefore, the sediment hardens into rock to preserve the fossil shape.

Explanation

If layers of sediment pile up, then the weight creates high pressure. If pressure and time act on the layers, then they undergo lithification. Therefore, the sediment hardens into rock to preserve the fossil shape.

15. A mold must be formed before a cast can be created.

True

False

If a cast is a replica made by filling a hole, then the hole must exist first. If the hole is defined as the mold, then the mold is a prerequisite for the cast. Therefore, the statement is true.

Explanation

If a cast is a replica made by filling a hole, then the hole must exist first. If the hole is defined as the mold, then the mold is a prerequisite for the cast. Therefore, the statement is true.

16. If a scientist finds a fossil that is a hollow indent in a rock, which type is it?

Cast

Trace

Mold

True Form

If the fossil is described as an "indent" or "hollow," then it is not a solid object. If it is the space where an organism used to be, then the logical classification is a mold.

Explanation

If the fossil is described as an "indent" or "hollow," then it is not a solid object. If it is the space where an organism used to be, then the logical classification is a mold.

17. A Jello-O mold used in a kitchen is most similar to a ______ fossil.

If a kitchen mold holds a liquid and gives it a specific shape, then it is the container. If a fossil mold holds minerals to give them a shape, then they function the same way.

Explanation

If a kitchen mold holds a liquid and gives it a specific shape, then it is the container. If a fossil mold holds minerals to give them a shape, then they function the same way.

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18. Which of the following are examples of sedimentary rocks where molds and casts might be found?

Sandstone

Shale

Granite

Limestone

If fossils form in rocks made of layers of sand, mud, or shells, then they are in sedimentary rocks. If sandstone, shale, and limestone are sedimentary, then they can hold fossils. If granite is volcanic, then it cannot.

Explanation

If fossils form in rocks made of layers of sand, mud, or shells, then they are in sedimentary rocks. If sandstone, shale, and limestone are sedimentary, then they can hold fossils. If granite is volcanic, then it cannot.

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19. What is the main difference between a mold and a cast?

One is a hole, the other is a solid filling

One is old, the other is new

One is from a plant, the other is from an animal

One is found in water, the other on land

If a mold is the impression left behind, then it is a cavity or hole. If a cast is the result of filling that hole, then it is a solid object. Therefore, the primary difference is their physical state (hollow vs. solid).

Explanation

If a mold is the impression left behind, then it is a cavity or hole. If a cast is the result of filling that hole, then it is a solid object. Therefore, the primary difference is their physical state (hollow vs. solid).

20. Soft body parts like muscles usually form molds and casts just as easily as hard shells.

True

False

If soft tissues decay very quickly, then they usually disappear before sediment can harden around them. If hard shells take much longer to dissolve, then the sediment has time to turn to rock. Therefore, soft parts rarely form these fossils.

Explanation

If soft tissues decay very quickly, then they usually disappear before sediment can harden around them. If hard shells take much longer to dissolve, then the sediment has time to turn to rock. Therefore, soft parts rarely form these fossils.