Reading a Rock Sequence: Superposition, Fossils and Correlation · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Reading a cliff like a timeline

Science · Earth's Systems · ages 15-16
Name ______________________   Date ____________

  1. An intrusion cuts through three layers. Which is youngest?

    • The bottom layer
    • The intrusion
    • All are the same age

  2. In an undisturbed stack, which layer is oldest?

    • The bottom layer
    • The middle layer
    • The top layer

  3. What makes a fossil a good index fossil?

    • A long life in one small bay
    • A short span over a wide area
    • A huge size and weight

  4. Beds above and below look parallel, yet time is missing. What is the gap?

    • An inclusion
    • A fault scarp
    • An unconformity

  5. A chunk of sandstone sits trapped inside shale. Which is older?

    • The sandstone chunk
    • The shale host
    • Both formed together

  6. An unconformity means some history is missing with no rock to show it.

    Circle one:   True   False

  7. Flat shale lies on an uneven granite surface. What must you conclude?

    • Granite is younger than the shale
    • An erosion gap sits between them
    • Superposition is broken here

  8. Two far cliffs share one short-span widespread species. What follows?

    • The cliffs are the same rock type
    • The layers match in age
    • Fossils prove nothing
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Reading a cliff like a timeline W1-mt_gIwqGoQsag-s1

  1. The intrusion · Cutters are younger than whatever they cut.
  2. The bottom layer · Superposition puts the first laid layer at the bottom.
  3. A short span over a wide area · Short plus widespread makes matches trustworthy.
  4. An unconformity · A buried erosion surface means lost chapters.
  5. The sandstone chunk · Inclusions are older than the rock holding them.
  6. True · Erosion removed the record before burial resumed.
  7. An erosion gap sits between them · The uneven contact hides time with no record.
  8. The layers match in age · That is correlation by a trusted index fossil.
Worksheet · LightMySky