The geologic time scale and the great extinctions

Grade 9 Science Worksheet

Circle the best answer.

1. 1.

   On the same 24-hour day, about how long is the Precambrian, from 4,600 to 541 million years ago, by Esme's math?

   • About 3 hours
   • About 21 hours
   • About 21 minutes
   • About 12 hours

2. Read this first

   Eras (USGS)

   Era	Began	Ended
   Paleozoic	541 million years ago	251.9 million years ago
   Mesozoic	251.9 million years ago	66 million years ago
   Cenozoic	66 million years ago	today

3. 2.

   The Paleozoic ran from about 541 to 251.9 million years ago (USGS). How does its length compare with the Cenozoic's 66 million years, by Jun's math?

   • About 8 times as long
   • About 4 times as long
   • About as long
   • About 4 thousand times as long

4. The Big Five (NPS)

   Extinction	About when	Species lost
   end-Ordovician	444 million years ago	86%
   Late Devonian	372 million years ago	75%
   end-Permian	251.9 million years ago	96%
   end-Triassic	200 million years ago	80%
   end-Cretaceous	66 million years ago	76%

5. 3.

   Which of the Big Five removed the largest share of species, by Kira's reading of the NPS table?

   • The end-Permian, about 96%
   • The Late Devonian, about 75%
   • The end-Cretaceous, since it is the most recent
   • The end-Ordovician, about 86%
6. 4.

   Which two of the Big Five do scientists link mainly to volcanic eruptions, by Milo's reading (NPS)?

   • The end-Permian and the end-Triassic
   • The Late Devonian and the end-Cretaceous
   • The end-Ordovician and the end-Permian
   • The end-Cretaceous and the end-Ordovician
7. 5.

   Branching tree that narrows, then spreads out again. Mammals first appeared in the Triassic but stayed small and few until after 66 million years ago (NPS). What does this show, by Noah's reading?

   • Life stayed low in variety after the extinction
   • Surviving mammals spread into the roles left open
   • Mammals caused the extinction
   • Mammals first appeared after 66 million years ago
8. 6.

   Permian, algae, sponges and bryozoans; after the end-Permian, stony corals; today, mostly stony corals. NPS: stony corals began building reefs after the end-Permian extinction, and reefs today are mostly stony corals. What does this show, by Pia's reading?

   • Reefs stopped forming after the end-Permian
   • Stony corals triggered the extinction
   • New groups can take over roles left open by an extinction
   • The same reef builders returned unchanged
9. 7.

   Branching tree that narrows, then spreads out again. Which pattern does NPS describe after mass extinctions, by Ren's reading?

   • Variety drops and stays low
   • Extinctions keep going at the high rate
   • Earth's time scale restarts at zero
   • Surviving groups branch into many new species
10. 8.

    Cross-section with a thin boundary layer. An iridium layer marks the Cretaceous-Paleogene boundary (NPS). Which change of eras does it mark, by Tala's reading?

    • From the Cenozoic back to the Mesozoic
    • From the Paleozoic to the Mesozoic, 66 million years ago
    • From the Mesozoic to the Cenozoic, 66 million years ago
    • From the Precambrian to the Paleozoic
11. 9.

    Ammonite shells below a boundary line, no ammonites above. Below a boundary, layers hold ammonites; above it, no ammonites appear (model data). Which boundary fits, by Zee's reading (NPS)?

    • A boundary from the last 1,000 years
    • The end-Cretaceous boundary, 66 million years ago
    • The end-Ordovician boundary, 444 million years ago
    • The start of the Mesozoic, after the Cenozoic
12. 10.

    NPS: trilobites became extinct at the end-Permian. A cliff layer holds trilobites. What does this tell a geologist, by Ari's reading?

    • The layer marks the end-Cretaceous boundary
    • The layer formed before about 251.9 million years ago
    • The layer formed in the last 66 thousand years
    • The layer is Cenozoic, from the most recent era