RockLicker · Grade 4 · Lesson 3 of 5

Layers Tell an Order

Use the order of undisturbed sedimentary layers to infer relative age without assigning years.

  • Grade 4
  • 40 minutes
  • Worksheet + teacher guidance
Back to Grade 4

What you will learn

In a sequence that has not been overturned, lower sedimentary layers were deposited before layers above them. Relative age gives an order, not a number of years.

Words to use

  • layer: a band of material
  • relative age: older or younger order
  • superposition: lower layers came first in an undisturbed stack

Evidence for this lesson

Imaginary undisturbed sequence: bottom A—sandstone; middle B—siltstone with a shell impression; top C—sandstone. No faults, overturning or numerical dates are supplied.

Use the supplied record as written; do not invent missing results.

Work through the activity

  1. 5 min · Build a stackPlace paper A down first, B on top, then C. Record the order of placement and compare it with the imaginary rock sequence.
  2. 15 min · Read the sequenceDraw the layers with A at the bottom and C at the top. Label oldest and youngest under the stated undisturbed assumption.
  3. 10 min · Ask about fossilsRead the fossil observations. Explain why a fossil in B would be associated with B, while a loose fossil beside the outcrop lacks that same clear context.
  4. 10 min · State limitsDiscuss why this model cannot tell the number of years between layers, and why overturned or faulted layers need more investigation.
RockLicker
GRADE 4 · LESSON 3

Layers Tell an Order

Draw on the printed sheet or write, type or dictate your response.
Draw on the printed sheet or write, type or dictate your response.
Draw on the printed sheet or write, type or dictate your response.
Draw on the printed sheet or write, type or dictate your response.

Responses stay in this open page only. Print before closing or changing pages; no student record is stored online.

Check your understanding

What does relative age tell you here?

Teacher & family guide · answers and assessment

Grade 4 · Layers Tell an Order

Learning goal: Use the order of undisturbed sedimentary layers to infer relative age without assigning years.

Expected responses

  1. A, then B, then C, assuming an undisturbed, non-overturned sequence.
  2. B, according to the supplied observation.
  3. No numerical dates are supplied.
  4. Its original layer is unknown unless documented; it may have moved.

Understanding check: The order of deposition. Superposition provides relative order under the stated assumptions, not calendar dates.

Watch for this misconception

Lower does not always mean older in overturned, disrupted or repeated sequences.

Assess the evidence

Look for the observations, calculation or explanation named in the learning goal. Accept accurate drawings and dictated responses. Use the expected responses to discuss reasoning; a correct guess without explanation is a starting point for another conversation.

Adapt and extend

Read prompts aloud, enlarge print or let a partner record the learner’s explanation. Turn the paper stack over and explain why the original assumption no longer matches the display.