RockLicker · Grade 6 · Lesson 3 of 5

Which Event Came First?

Combine superposition and cross-cutting relationships to build an event sequence.

  • Grade 6
  • 50 minutes
  • Worksheet + teacher guidance
Back to Grade 6

What you will learn

An undisturbed, non-overturned layer stack gives relative order. A geological feature that cuts another formed after what it cuts. Later layers can cover earlier structures.

Words to use

  • cross-cutting: one feature cuts another
  • intrusion: molten material entering older rock
  • relative sequence: ordered events

Evidence for this lesson

Imaginary section: undisturbed layers A then B; intrusion D cuts A and B. Later layer C covers both B and the top of D. No faults, overturning or numerical dates are supplied.

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

Work through the activity

  1. 10 min · Draw the sectionDraw A below B below C. Add intrusion D crossing A and B but ending at the base of C. Follow the explicit relationships, not artistic guesses.
  2. 15 min · Order evidenceUse superposition to place A before B. Use cross-cutting to place D after A and B. Use the stated cover relationship to place C after D.
  3. 15 min · Explain each linkWrite one evidence sentence for every neighboring pair in your event order. State that no numerical ages have been supplied.
  4. 10 min · Test a changeRedraw D cutting C as well. Explain how the sequence would change and what new evidence caused the revision.
RockLicker
GRADE 6 · LESSON 3

Which Event Came First?

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

An intrusion cuts layer B. The intrusion is …

Teacher & family guide · answers and assessment

Grade 6 · Which Event Came First?

Learning goal: Combine superposition and cross-cutting relationships to build an event sequence.

Expected responses

  1. A bottom, B middle, C top, D crossing A and B but covered by C.
  2. A, B, D, C under the stated assumptions.
  3. D cuts B, so is later than B; C covers D, so is later than D.
  4. A, B, C, D if the revised D cuts all three layers.

Understanding check: younger than B. The cut rock had to exist before the intrusion passed through it.

Watch for this misconception

A sequence provides order, not elapsed years; disrupted sequences need additional evidence.

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. Add an erosion surface before C and discuss which event it could remove from the visible record.