The geologic time scale and the great extinctions

Grade 9 Science Worksheet - Building Confidence

Circle the best answer.

1. 1.

   Time-scale bar. Earth formed about 4,600 million years ago, and the Precambrian ended about 541 million years ago (USGS). About what share of Earth's history is the Precambrian, by Ari's math?

   • About 1%
   • About 88%
   • About 12%
   • About 50%
2. 2.

   Time-scale bar drawn to scale. On a USGS time-scale bar drawn to scale, which part takes up most of the length, by Bo's reading?

   • The Precambrian
   • The Mesozoic, with the dinosaurs
   • The Cenozoic, our own era
   • The Paleozoic, with early sea life

3. 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

4. 3.

   The Mesozoic ran from about 251.9 to 66 million years ago (USGS). About how long did it last, by Kira's math?

   • About 66 million years
   • About 186 million years
   • About 318 million years
   • About 186 thousand years
5. 4.

   Put the three eras of the last 541 million years in order, oldest first, by Jun's reading (USGS).

   • Mesozoic, Paleozoic, Cenozoic
   • Paleozoic, Mesozoic, Cenozoic
   • Cenozoic, Mesozoic, Paleozoic
   • Paleozoic, Cenozoic, Mesozoic
6. 5.

   When does the Paleozoic end and the Mesozoic begin, by Luz's reading (USGS)?

   • About 66 million years ago, when the Cenozoic began
   • About 541 million years ago, at the Precambrian's end
   • About 251.9 thousand years ago
   • About 251.9 million years ago
7. 6.

   In a thick stack of undisturbed rock layers, where would Mesozoic layers sit, by Milo's reading?

   • Mixed in at random
   • Above Paleozoic layers and below Cenozoic layers
   • Below Paleozoic layers, since the Mesozoic is older
   • Above Cenozoic layers, at the very top

8. 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%

9. 7.

   What do scientists link to the extinction 66 million years ago, by Noah's reading (NPS)?

   • Flood basalt eruptions in Siberia
   • A slow cooling over 100 million years
   • An asteroid impact that formed the Chicxulub crater
   • A glaciation on Gondwana
10. 8.

    What do scientists think triggered the end-Permian extinction, by Pia's reading (NPS)?

    • Glaciers spreading over the Southern Hemisphere
    • Flood basalt eruptions in Siberia
    • An asteroid impact in the Yucatan
    • Forests spreading across the land
11. 9.

    NPS says more than 99% of species that have lived are now extinct. What does this show, by Zee's reading?

    • Most species lasted billions of years
    • Extinction is a normal, ongoing part of life's history
    • Life on Earth keeps shrinking toward zero
    • Extinction happened just five times
12. 10.

    Branching tree that narrows, then spreads out again. What usually follows a mass extinction, by Esme's reading (NPS)?

    • The same species return unchanged
    • Earth's history starts over
    • Bursts of new species among the surviving groups
    • Life stays at low variety from then on