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 12%
   • About 50%
   • About 1%
   • About 88%
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 Paleozoic, with early sea life
   • The Mesozoic, with the dinosaurs
   • The Cenozoic, our own era

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

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

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

6. 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%

7. 5.

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

   • An asteroid impact that formed the Chicxulub crater
   • Flood basalt eruptions in Siberia
   • A slow cooling over 100 million years
   • A glaciation on Gondwana
8. 6.

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

   • Flood basalt eruptions in Siberia
   • Glaciers spreading over the Southern Hemisphere
   • An asteroid impact in the Yucatan
   • Forests spreading across the land
9. 7.

   What do scientists link to the end-Ordovician extinction, by Ren's reading (NPS)?

   • Mammals spreading across the land
   • A rapid glaciation and its quick retreat
   • An asteroid impact that left a crater near the equator
   • The opening of the Atlantic Ocean
11. 8.

    What makes an extinction a mass extinction, by Tala's reading (NPS)?

    • A single species becoming extinct
    • A change of season
    • Extinctions at the usual slow rate
    • A spike in extinctions over a short span of geologic time
12. 9.

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

    Use the picture in question 8.

    • Life on Earth keeps shrinking toward zero
    • Extinction is a normal, ongoing part of life's history
    • Extinction happened just five times
    • Most species lasted billions of years
13. 10.

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

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