Name: ______Date: ______Period: ____

Chapter 9 Investigation: Modeling the Geologic Time Scale

Question:

How can the geologic time scale be represented in a way that allows a clearer visual understanding?

Materials:

  • 5+ meters of adding machine tape
/
  • meterstick

  • pencil
/
  • color pencils

Day 1 Procedure:

  1. Draw a 5 meter line down the middle of your paper. This will be your timeline.
  2. Draw a straight line across one end and label it “present”. Draw 5 more lines exactly 1 meter apart. Label the closest to the present “1 billion years ago.” Label the second line “2 billion years ago,” and so on. The last line will be labeled “5 billion years ago.”

Scale:

1 meter = 1 billion years

10 centimeters = 100 million years

1 centimeter = 10 million years

1 millimeter = 1 million years

  1. Mark the events shown on the other side of this paper on your time scale.

Day 2 Procedure:

  1. Trace over the line for each ERA with a different color pen or pencil.
  2. Illustrate your timeline!Your drawings should represent the many events that occurred and the many life forms (plant and animal) that were present. Be sure that your illustrations are colorful and representative.

Inferred Ages of Events in Years before Present

Event Label / Number of Years Ago / Measurement
First mammals and dinosaurs / 200 million / 20 cm
Origin of the Earth / 4.6 billion
Beginning of the Carboniferous Period / 345 million
Oldest fungi / 1.7 billion
Trilobites are dominant / 490 million
Beginning of the Jurassic Period / 190 million
Beginning of the Devonian Period / 395 million
Last Ice Age / 10,000
Beginning of the Cretaceous Period / 136 million
Beginning of the Paleozoic Era (first abundant fossils) / 570 million
Oldest rocks known / 4.2 billion
Beginning of the Quaternary Period / 1.8 million
Oldest carbon from plants / 3.6 billion
Beginning of the Ordovician Period / 500 million
First birds / 160 million
Beginning of the Cenozoic Era / 65 million
First humanlike creatures / 3.5 million
Beginning of the Silurian Period / 430 million
First reptiles / 290 million
Beginning of the Mesozoic Era / 225 million
Pangaea is created / 260 million
Humans begin to make tools / 2 million
Beginning of the Permian Period / 280 million
Oxygen begins to accumulate in the atmosphere / 2.5 billion
First fish appear / 443 million

Post-Lab Questions

Observe and Analyze:

  1. The time from 4.6 billion years ago until the beginning of the Paleozoic era is called Precambrian time. Find the part of your time scale that represents Precambrian time.

What do you notice when you compare the length of Precambrian time with all the other areas in the geologic time scale combined?

______

  1. How does the era that includes the present – the Cenozoic era – compare in length with the other eras?

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  1. Where are the two main extinction events on your timeline?

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Conclude:

  1. Where are most of the life forms on your timeline grouped?

______

  1. What limitations or difficulties did you have in making or interpreting this model of the geologic time scale?

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