Put rock layers in order

Grade 9 Science Worksheet - Building Confidence

Circle the best answer.

1. 1.

   On card K, Ari compares Unit 3 with dike D. Which is older, and why?

   • Dike D, because it is basalt and Unit 3 is limestone
   • Dike D, because it reaches deeper than Unit 3 does
   • Neither; one cannot be older without a date
   • Unit 3, because dike D cuts through it
2. 2.

   On card H, Bo asks which came first, the tilting of Units A to C or the laying down of flat Unit D?

   • Unit D came first, then everything was tilted after it
   • Tilting came first; D was laid on the eroded edges
   • They happened together, as Unit D slowly formed
   • Units A to C were tilted after D had covered them
3. 3.

   On card S, Jun decides whether the basalt sheet is older or younger than Unit 3. Which answer fits the evidence?

   • Younger: Unit 3 holds basalt pebbles, so Unit 3 came first
   • Older: Unit 3 holds basalt pebbles, so basalt came first
   • Neither can be known without a radiometric date
   • Younger: it baked Unit 2, so it flowed in after Unit 3
4. 4.

   Fault F on card K offsets dike D and Unit 4. What does Kira learn about Unit 4 and the fault?

   • Unit 4 came first, and fault F broke it later
   • Fault F came first, and Unit 4 was laid over it
   • Unit 4 is the youngest event, since it is the top layer
   • Both formed at the same moment
5. 5.

   “(made up), bottom to top:” On card T, Luz asks which is older, the basalt sheet or Unit 3. Heat baked Unit 3 above the sheet.

   • The basalt, because it lies below Unit 3 in the stack
   • Same age, because they touch along one flat line
   • The basalt, because it is much harder rock than Unit 3
   • Unit 3: the basalt baked it, so the basalt came in later

6. Read this first

   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.

7. 6.

   Noah needs one fossil to match rocks on different continents. Which is the best index fossil?

   • S: it lived for one slice and is found worldwide
   • P: it lived the longest, so it fits the most rock
   • Q: it lived a short time, though in one basin alone
   • R: it is worldwide, though it lived three slices
8. 7.

   A layer holds only fossil P. What can Pia safely say about its age?

   • It formed in slice 4, the last slice P lived
   • It formed in slice 1, when P first appeared
   • It formed sometime in slices 1 to 4; P alone cannot say which
   • Its age is unknown, since a fossil cannot narrow time whatsoever
9. 8.

   On card H, Ren studies the wavy surface between Unit C and flat Unit D. What does it show?

   • Nothing is missing; C simply ends and D starts
   • Time is missing: tilted layers eroded before D formed
   • The layers were laid down in one single event
   • D is older, because it stayed flat and undisturbed

10. NPS (Grand Canyon)

    The Layered Paleozoic Rocks are about 510 Ma; the Vishnu Basement Rocks are about 1.75 billion years (1,750 Ma). At the Great Unconformity they touch directly.

11. 9.

    At one Grand Canyon spot, 510 million-year-old (510 Ma) sandstone rests on 1.75 billion-year-old schist. What does Tala infer?

    • The sandstone is older, because it sits on top of the schist
    • About 1.2 billion years of rock record are missing there
    • Nothing is missing there, because the two rocks touch directly
    • About 510 million years are missing from the record there
12. 10.

    Zee sees flat layers, but the boundary between two of them is rough and cuts into the lower layer. What does it mean?

    • It is a normal boundary, so no time is missing
    • The upper layer is older, since it is pressed into the lower
    • Both layers formed at the same moment
    • Erosion cut the lower layer before the upper layer was laid down