Lesson Worksheet: The Geologic Time Scale Geology

In this worksheet, we will practice recognizing the geologic time scale and how geological time is classified and divided up using dating methods such as radiometric dating and index fossils.


Which is the correct order that represents the divisions of geologic time in descending order of duration?

  • AA period, an epoch, an era, an eon
  • BAn eon, an era, a period, an epoch
  • CAn eon, an era, an epoch, a period
  • DAn era, an eon, an epoch, a period
  • EAn era, an eon, a period, an epoch


Which of the following are eras in Earth’s geological history?

  • AProterozoic, Phanerozoic, and Mesozoic
  • BPaleozoic, Mesozoic, and Permian
  • CPaleozoic, Mesozoic, and Cenozoic
  • DPhanerozoic, Mesozoic, and Cenozoic
  • ETriassic, Jurassic, and Cretaceous


True or False: Radiometric dating uses the decay of radioactive substances to determine the age of Earth, which is approximately 4.6 billion years old.

  • ATrue
  • BFalse


True or False: One of the reasons the fossil record is incomplete is that most organisms either decay or are eaten by other organisms soon after death, and so they are not preserved.

  • ATrue
  • BFalse


At the end of which period did dinosaurs become extinct?

  • AJurassic
  • BTriassic
  • CPermian
  • DSilurian
  • ECretaceous


Which animals dominated the Mesozoic era?

  • AInsects
  • BDinosaurs
  • CBirds
  • DMammals


Which of the following represents approximately 87% of Earth’s age?

  • APrecambrian
  • BCenozoic
  • CCambrian
  • DPhanerozoic
  • EPermian


What is the most recent epoch in geological history according to the geologic time scale?

  • APhanerozoic
  • BCenozoic
  • CQuaternary
  • DHolocene
  • EPermian


What is the index fossil most commonly seen in rocks deposited in the Triassic period?

  • AAmmonite
  • BMammoth
  • CSeed fern
  • DTrilobite
  • ENummulite


True or False: Earth’s geological history is divided up into a series of time intervals of equal lengths.

  • ATrue
  • BFalse

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