Rock layers as evidence of change · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Reading the story in rock layers

Science · Space Systems & Earth's History · ages 9-10
Name ______________________   Date ____________

  1. A scientist finds a fossil in the very bottom layer of rock. What does that likely tell her?

    • The organism lived very recently
    • The organism lived a very long time ago
    • The organism is still alive today

  2. In a cliff with several rock layers, which layer is usually the oldest?

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

  3. Rock layers, or strata, form in a single day.

    Circle one:   True   False

  4. Scientists find a rock layer bent into a wave shape instead of lying flat. What does this pattern most likely show?

    • The layer formed underwater and was never disturbed
    • Forces pushed and folded the land sometime after the layer formed
    • The layer is the youngest one in the area

  5. Layer A sits above Layer B. Layer B holds fossils of tiny sea creatures that died out long ago. What does this tell you about Layer B?

    • Layer B is older than Layer A
    • Layer B is younger than Layer A
    • Layer B formed on the same day as Layer A

  6. This chart shows the age of two rock layers in millions of years. How many millions of years older is the bottom layer than the top layer?

    Top10Bottom90

    Answer: ______________

  7. A hillside has flat rock layers full of ocean fish fossils, but the hill is far from any ocean today, and the layers are tilted upward on one side. What best explains these clues together?

    • The hill was always dry land, and the fossils formed there naturally
    • The area was once covered by ocean, and the land later got lifted and tilted
    • A flood placed the fossils there very recently

  8. From bottom to top, a canyon wall shows Layer 1, Layer 2, Layer 3, Layer 4. Ben says Layer 4 must be the oldest because it is on top. Is he right?

    Layer 1Layer 2Layer 3Layer 4
    • No, Layer 1 is oldest because it is at the bottom
    • No, Layer 4 is oldest because it is the thickest
    • Yes, Layer 4 is the oldest layer
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Answer key

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

Reading the story in rock layers W1-mt_GheLsWvrJ4-s1

  1. The organism lived a very long time ago · Bottom layers are usually the oldest, so fossils found there come from organisms that lived long ago.
  2. The bottom layer · New layers always settle on top of older ones, so the deepest layer formed first.
  3. False · Strata build up slowly, often over thousands or millions of years, as new material settles on top of old.
  4. Forces pushed and folded the land sometime after the layer formed · Layers start out flat, so folding or tilting is a clue that the land was pushed or squeezed later on.
  5. Layer B is older than Layer A · Because Layer B sits below Layer A, it formed first, and its fossils show organisms that lived earlier in time.
  6. 80 · 90 million years minus 10 million years equals 80 million years older.
  7. The area was once covered by ocean, and the land later got lifted and tilted · Ocean fossils show the area was once underwater, and the tilted layers show the land moved afterward, together revealing how the landscape changed.
  8. No, Layer 1 is oldest because it is at the bottom · The order from bottom to top matches the order the layers were laid down, so Layer 1 formed first.
Worksheet · LightMySky