Geologic time scale activity: a 4.5-meter Earth history string, 6–8

1. Share the U.S. Geological Survey fact: Earth is about 4.54 billion years old. Ask students to guess where on the string dinosaurs and humans belong.
2. Stretch the string along a wall or hallway. Mark the left end "Earth forms" and the right end "today".
3. Explain the scale: 1 meter equals 1 billion years, 1 centimeter equals 10 million years, 1 millimeter equals 1 million years.
4. Place the last non-bird dinosaurs, about 66 million years ago: 66 millimeters from the right end.
5. Place modern humans, about 300,000 years ago: a third of a millimeter from the end. Students try to mark it.
6. Groups research two more events from a reliable source (such as the first fish or the first flowering plants), calculate the position and pin them.
7. Discuss: what does this tell you about how long Earth changed before people were here?

Safety: string runs along a wall at waist height, never across walkways.

Differentiation: students who need support place the three events given. Students who are ready redo the scale for a 100-meter football field and compare. English learners can use "___ happened ___ years ago, so it goes ___ from the end."

Quick check: ask: "At this scale, how far from today is something that happened 250 million years ago?" (250 millimeters, or 25 centimeters.)

Educators, how do you help students feel how long deep time is? Share your scale or analogy in the replies.