The geologic time scale and the great extinctions

Grade 9 Science Worksheet - Building Confidence

Circle the best answer.

1. 1.

   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

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

   • About 318 million years
   • About 186 thousand years
   • About 186 million years
   • About 66 million years
4. 3.

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

   • About 251.9 million years ago
   • About 66 million years ago, when the Cenozoic began
   • About 251.9 thousand years ago
   • About 541 million years ago, at the Precambrian's end
5. 4.

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

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

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)?

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

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

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

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

   • A rapid glaciation and its quick retreat
   • The opening of the Atlantic Ocean
   • Mammals spreading across the land
   • An asteroid impact that left a crater near the equator
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
    • Most species lasted billions of years
    • Extinction happened just five times
13. 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
    • Bursts of new species among the surviving groups
    • Earth's history starts over
    • Life stays at low variety from then on