Title
Activity: Timeline of Earth
NGSS Science and Engineering Practices
NGSS Crosscutting Concepts
NGSS Disciplinary Core Ideas
Table of Contents
Materials
- Table 7.4.
- Meter stick or measuring tape
- Rope or yarn (at least 5 m length)
- Masking or painter’s tape
- Markers
- Index cards
Procedure
- Cut rope for a timeline
- Measure out and cut 4.6 m of straight rope or yarn.
- This 4.6 m length of rope will represent the entire 4.6 billion years since the formation of Earth.
- Wrap the two rope ends with masking tape to prevent fraying.
- Label one end of the rope as “present day” and the other end as “4.6 billion years ago.”
- Use the meter stick to measure 0.5 m from the present day end of the rope.
- Use masking tape to label this 0.5 m point as “500 million years ago.”
- Continue measuring and labeling rope segments, in 500 million increments, until the end of rope.
- Prepare event index cards
- Complete the missing cells in the list of several major events in Earth’s history (Table 7.4.).
- On one side of a blank index card, write the name of the event and a brief description of it.
- Write the event date on the opposite side of the index card.
- Attach event index cards to the timeline at the appropriate locations.
- Present your timeline to your classmates.
Activity Questions
- If the entire 4.6 m-long rope represents 4.6 billion years, how much time is represented by the following lengths:
- 10 cm
- 1 mm
- The term “Precambrian” refers to the period of time before the Cambrian Explosion around 542 million years ago.
- What is the significance of the Cambrian Explosion in terms of life on Earth?
- How does the length of Precambrian time compare to amount of time after the Cambrian Explosion?
- The Great Oxygenation Event was the sudden increase in oxygen gas (O2) concentration in the atmosphere, beginning around 2.5 billion years ago (for more detail, see Building Blocks of Life).
- What earlier evolutionary event likely caused the Great Oxygenation Event?
- How do you think organisms survived before the Great Oxygenation Event in a world with low oxygen gas concentration?
- The midpoint of the timeline is 2.3 billion years ago (2.3 m from either end). Use your own words to describe life on Earth before this point on the timeline.
