Put rock layers in order

Grade 9 Science Worksheet - Challenge Me

Circle the best answer.

1. 1.

   On card Z, which pair of events can Ari NOT put in order?

   • Unit 2 and Unit 4: an erosion surface lies between them
   • Dike K and dike M: both are younger than Unit 5 but never touch
   • Granite G and Unit 4: pebbles inside Unit 4 say nothing about order
   • Granite G and dike K: they never touch, so nothing links them

2. Read this first

   Column Q (made up), bottom to top

   Unit 1; Unit 2 with an ash bed dated 320 Ma; Unit 3; an erosion surface; Unit 4 with an ash bed dated 250 Ma. Dike D cuts Units 1 to 3, ends at the erosion surface, and is dated 280 Ma.

3. 2.

   Using the dated ash beds and dike on card Q, what is the most time Esme can say is missing at the erosion surface?

   • 30 million years, from the 320 Ma ash to the 280 Ma dike
   • At most 70 million years, from the 320 Ma ash to the 250 Ma ash
   • No time is missing: an erosion surface just marks a pause
   • Exactly 70 million years, from the ash beds
4. 3.

   Unit 3 limestone is 40 m thick; Unit 4 siltstone is 10 m thick. Jun's friend says Unit 3 is 40 m thick and Unit 4 is 10 m thick, so Unit 3 is four times older. Which reply is best?

   • Wrong: just dikes and faults can be compared by thickness
   • Correct: thicker layers take longer, so Unit 3 is four times older
   • Thickness shows sediment amount, not time; rates and gaps vary
   • Wrong: Unit 4 is on top, so it must be four times older

5. NPS

   At the Great Unconformity, rocks 1.75 billion years old lie under 510 million-year-old rocks. Elsewhere in the canyon, Supergroup rocks about 1.25 billion years old lie between them.

6. 4.

   Kira's classmate says the Great Unconformity proves nothing happened on Earth for 1.2 billion years. Which reply is best?

   • No: the gap is local; Supergroup rocks elsewhere fill part of it
   • No: the Supergroup rocks are older than the schist is
   • Yes: no rocks formed anywhere during that long time
   • Yes: the schist and sandstone touch, so no time has passed

7. Hill H (made up)

   Units A, B and C lean 40 degrees to the east, with A lowest. A wavy erosion surface cuts across their tilted edges. Flat Units D and E lie on that surface, D below E. Dikes form upright. Dike X is upright and cuts Units A to C, ending at the wavy surface. Dike R cuts Units A to E.

8. 5.

   Milo adds two dikes to hill H: upright X cuts A to C and ends at the wavy surface; R cuts A to E. Dikes form upright. Which order is right?

   • Tilting, dike X, erosion, Units D and E, dike R
   • Tilting, dike X, erosion, dike R, Units D and E
   • Dike X, tilting, erosion, Units D and E, dike R
   • Tilting, erosion, dike X, Units D and E, dike R

9. Table, Fossil ranges (made up), with columns Fossil, Time slices lived (1 oldest, 6 youngest), Where found

   P, 1 to 4, worldwide; Q, 2 to 3, one basin only; R, 3 to 5, worldwide; S, 5, worldwide. Note: A time slice is one equal span of time.

10. 6.

    Noah finds basalt sheet B between layer m (Q and R, below) and layer n (S, above). It baked both. When could B have formed?

    • Slice 3, the age of layer m
    • Slice 5 or later, after layer n formed
    • Slice 4 exactly, halfway between the layers
    • Between slices 3 and 5, as the layers surround it
11. 7.

    Granite G, dated 1,700 Ma, holds chunks of schist. Sandstone about 510 Ma lies on the eroded granite. What can Pia say about the schist?

    • The schist is younger than 1,700 Ma, since the granite surrounds it
    • The schist is older than 1,700 Ma, as its chunks sit inside
    • The schist is younger than 510 Ma, since the sandstone covers it
    • The schist is exactly 1,700 Ma, the age of the granite
12. 8.

    Layer X is older than layer Y at two sites. Ren's friend says X formed exactly 5 million years before Y. What would test that?

    • Count the fossils in each layer and compare the counts
    • Measure the thickness of rock between X and Y
    • Radiometric dates from ash or igneous rock around each layer
    • Check that X lies below Y at a third distant site

13. Table, Fossil ranges (made up), with columns Fossil, Time slices lived (1 oldest, 6 youngest), Where found

    P, 1 to 4, worldwide; Q, 2 to 3, one basin only; R, 3 to 5, worldwide; S, 5, worldwide. Note: A time slice is one equal span of time.

14. 9.

    Two cliffs each have a limestone. Cliff 1's holds fossil Q; Cliff 2's holds fossil S. Tala says they match. Does the evidence support that?

    • Cannot tell: fossils cannot be used to date limestone
    • Yes: both limestones lie at the same height in their cliffs
    • No: Q marks slices 2 to 3 and S marks slice 5
    • Yes: the same rock type means the same age everywhere
15. 10.

    Zee claims the erosion surface under Unit 4 formed between 190 Ma and 160 Ma. Which new finding would most weaken the claim?

    • A new date of 185 Ma for dike D
    • Another dike like D found in Unit 2
    • A fossil in Unit 4 that also lived during Unit 3 times
    • A re-dating of dike D to 150 Ma, younger than the ash