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Just-in-Time Teaching (JiTT) WarmUp Activity: Geologic Dating

Laura Guertin, Penn State University Delaware County
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1) How are zircons formed?

2) Which of the following statements describes relative geologic dating?
a) the Triceratops and Tyrannosaurus rex went extinct at the same time
b) dinosaurs came later than horseshoe crabs
c) the southern Atlantic Ocean began forming 20 million years after Pangaea split apart
d) the oldest piece of Atlantic Ocean crust is ~135 million years old, while the oldest piece of Pacific Ocean crust is ~165 million years old
e) orangutans separated from the hominid lineage 14 million years ago

3) Which of the following statements describes absolute geologic dating?
a) the Triceratops evolved after the Stegosaurus
b) the dinosaurs died out 60 million years before humans split from chimps
c) gorillas evolved before chimps
d) the northern Atlantic Ocean formed before the southern Atlantic Ocean
e) the Ice Ages ended 10,000 years ago, before the Cambrian Explosion ~545 million years ago

4) Why are zircons the most reliable timepiece we have for looking at Earth's early history?

Student Responses:

See the Just-in-Time Teaching page on assessment for information and ideas on how to evaluate student responses.

References and Notes:

Articles that students may be assigned to read for this set of questions include (but are not limited to):

Zircon Chronology: Dating the Oldest Material on Earth, Earth: Inside Out (more info) , American Museum of Natural History.

The use of Just-in-Time Teaching is discussed in detail on the JiTT Starting Point page.

Additional information on JiTT is available in the book:


Geoscience:Geology:Historical Geology, Geochemistry:Radioisotopes

Resource Type

Activities:Classroom Activity:Just in Time Teaching

Grade Level

College Lower (13-14):Introductory Level

Ready for Use

Ready to Use

Earth System Topics

Time/Earth History, Solid Earth:Earth Materials


Teach the Earth:Teaching Environments:Intro Geoscience, Teach the Earth:Course Topics:Geochemistry