Earth 22

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Earth’s Past

Beginning with the Precambrian period, Earth’s past is a vast series of time-periods – chronological dating that relates geological strata to time. The geologic time scale (GTS) is used by geologists, paleontologists, and other Earth scientists to describe the timing and relationships of events that have occurred during Earth’s history. The Precambrian started with the origin of the earth about 4.5 billion years ago and ended 570 million years ago. The timeline is grouped into eons, eras, and periods (each successively smaller units of time).

Lesson 1 (or “Day 1”) Material
  • Day 1 – Instructor Presentation
  • Day 1 – Instructor Supplement (K-Pg boundary)
  • Day 1 – Student Handout
Lesson 2 (or “Day 2”) Material
Lesson 3 (or “Day 3”) Material
Lesson 4 (or “Day 4”) Material


12:07 A Brief History of Geologic Time

1:58 How To Make Pangaea | Geology Unit

4:04 Geologic “Eras”, animated

Compare Contrast and Debate

Background: Scientists use the expressions Eon, Era, Period, and Epoch to convey very long periods of time through shorter periods of time. This approach can be confusing at times – especially to  students.

  • Position A – The approach used, even though it can be confusing, is appropriate and meaningful.
  • Position B – A simpler approach should be identified and used. This would help everyone – especially students.

Resources Documents and Links

Special Notes and Notices

Instructor Emphasis:

  • Science & Engineering Practice: Analyze and interpret data.
  • Cross-Cutting Concept: Systems and System Models.

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