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Watch the movie to learn how scientists study rock strata to make a timeline of Earth’s history. As you watch, record any observations that help you answer the Guiding Question.

1
According to the movie, how do rock strata form?

A
Gravity causes sediment to settle in layers

B
Earthquakes create large slices in existing rock

C
Layers are pushed upward from Earth’s core

D
Changes in air pressure push rocks downward
2
Fill in the blanks to complete the sentences. Not all answer choices will be used.

The law of superposition allows geologists to determine the
ages of rock layers. Although it doesn’t tell us exactly how old the strata are, this law tells us
rock layers form on top of
ones.

3
Rock strata are often folded, as shown in this image. If the pink layer has an absolute age of 350 million years, which two of these statements must be true?

afolded, wavy rock strata. From top to bottom, the strata are labeled Tan, Beige, Brown, Gray, Pink, Light green, and Khaki.

The khaki layer was formed after the pink layer

The light green layer is more than 350 million years old

The brown layer is also 350 million years old

The pink layer folded more than 350 million years ago

The tan layer is less than 350 million years old
4
Fill in the blanks to complete the sentences. Not all answer choices will be used.

William Smith observed that
are unique to specific rock layers. This means that rocks with the same fossils must have formed
time, even if they are located thousands of miles apart.

5
Trilobites are sea creatures that lived about 500 million years ago. Their fossils have been found in rock strata all over the world, as shown in the map above. What can you conclude from this information?

A world map has 9 white stars placed on 6 continents to indicate the locations of trilobite fossils. An inset photo shows a large trilobite fossil. The fossilized organism looks like a large insect with many sets of legs. It has a shell similar to a horseshoe crab.

A
Trilobites are found in rock strata above more recent fossils

B
Much of the world was covered with water 500 million years ago

C
Trilobites were the only life forms on Earth 500 million years ago

D
The world’s climate has remained constant for 500 million years

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1 answer

Based on the information provided, here are the answers to the questions related to the movie about how scientists study rock strata to create a timeline of Earth's history:

  1. According to the movie, how do rock strata form? Answer: A - Gravity causes sediment to settle in layers.

  2. Fill in the blanks to complete the sentences. Not all answer choices will be used. The law of superposition allows geologists to determine the relative ages of rock layers. Although it doesn’t tell us exactly how old the strata are, this law tells us younger rock layers form on top of older ones.

  3. If the pink layer has an absolute age of 350 million years, which two of these statements must be true?

    • The pink layer folded more than 350 million years ago.
    • The tan layer is less than 350 million years old.

  4. Fill in the blanks to complete the sentences. Not all answer choices will be used. William Smith observed that fossils are unique to specific rock layers. This means that rocks with the same fossils must have formed at the same time, even if they are located thousands of miles apart.

  5. What can you conclude from this information about trilobites? Answer: B - Much of the world was covered with water 500 million years ago.

Feel free to ask if you need further elaboration or additional questions!