Module #7 - Geologic Time


1. Watch the Video of the Day: Geological Timescale (lecture) (8 minutes) and make point form notes in your digital video journal. Please make sure that you SHARE your document with Mr. Durk.

2. Read the following information below in Part 1: Background and Terminology. Follow all hyper-links (BLUE) to external websites for activities, demonstrations and videos (if applicable). Copy only KEY information (i.e. the highlighted terms) to your notebook (or in google docs). 

3. Complete Part 2: Understanding Geological Time Activities see below) and complete in class with the handouts provided to you by Mr. Durk.

DUE DATE:  Before Module #8 (Friday April 1st)

Part 1: Background and Terminology

Record Icon
Please remember to record all definitions and content in your virtual notebook. Definitions can be found by clicking on highlighted words.

The Scale of Geological Time

The earth’s origins date back to 4.6 billion years ago. For most of us, it is quite difficult to fathom such an enormous number. Even when studying ancient history, historians might study as far back as 5,000 years ago. In order to study Earth’s evolution, however, geologists have created the Geological Time Scale modeled on major geological and biological events dating back 4.6 billion years. Geologic time is divided into eons and eras, which are further categorized into eleven periods. Finally, the Quaternary and Tertiary periods within the latest Cenozoic Era have been dissected into seven epochs.

Record Icon

View the following links and note the major events for every era in your virtual notebook. Be sure to keep a copy of the above Geological Time Scale.

External Links

Refer to this link to view and download the Geological Time Scale.

External LinksLink to Web Geological Time Machine.
External Links

Link to Earth’s Timeline.

  1. Spheres of the Earth:

Everything in Earth's system can be placed into one of four major spheres: the lithosphere (land), hydrosphere (water), biosphere (living things), and atmosphere (air). Although these spheres can be studied independently, they are all part of the same interconnected system. Therefore, changes in any sphere ultimately affect the other spheres as well. The current "balance" among these complex interactions makes it possible for life to flourish on Earth.

Questions IconCheck Your Understanding

  1. The Ice sheets are retreating from Europe and North America and all of recorded human history occurs during the:

    a) Cenozoic-tertiary- Pliocene epoch.
    b) Cenozoic-Quaternary- Holocene epoch.
    c) Cenozoic-Quaternary- Pleistocene epoch.
    d) Mesozoic era.

    Answer Button Answer


  2. Between 5 and 1.6 million years ago, the climate became cooler and drier; mammals were the dominant life form and a rapid evolution of primates occurred during the: 
    a) Cenozoic-tertiary- Pliocene epoch.
    b) Cenozoic-Quaternary- Holocene epoch.
    c) Cenozoic-Quaternary- Pleistocene epoch.
    d) Paleozoic era.

    Answer Button Answer


  3. The sudden mass extinction of dinosaurs and the killing of 70% of all living things occurred during the:
    a) Mesozoic-Triassic period. 
    b) Mesozoic-Jurassic period.
    c) Mesozoic-Cretaceous period.
    d) Paleozoic era. 

    Answer Button Answer


  4. Is the following statement true or false? The Mesozoic era is divided into three epochs, Triassic, Jurassic, and Cretaceous. 

    Answer Button Answer


  5. Coal begins to form and the first true reptiles appear during the: 
    a) Paleozoic Cambrian period. 
    b) Paleozoic Silurian period. 
    c) Paleozoic Carboniferous period. 
    d) Paleozoic Permian period. 

    Answer Button Answer


  6. Vertebrates are found in the ocean and primitive life on land during the: 
    a) Paleozoic Cambrian period.
    b) Paleozoic Ordovician period.
    c) Paleozoic Devonian period.
    d) Paleozoic Permian period.

    Answer Button Answer


  7. How many eras are there in an eon?

    Answer Button Answer


  8. Is the following statement true or false? The Hadean Eon has no geological record.

    Answer Button Answer


  9. Single celled organisms appear. The continents, oceans, and atmosphere are forming during the:
    a) Precambrian, Hadean eon. 
    b) Precambrian, Archean eon. 
    c) Precambrian, Proterozoic eon. 
    d) Phanerozoic eon.

    Answer Button Answer


  10. Geologists have discovered evidence of two mass extinctions. The first was during the _______________ and the second was during the _______________.

    Answer Button Answer

external linkResources

  1. Geologic Time Scale
  2. Web Geological Time Machine, University of California Museum of Paleontology
  3. Earth’s timeline, MSNBC

Relative and Absolute Time

The Geological Time Scale is the product of years of research by many scientific minds. It is based on both relative and absolute time.

Relative time is a time period in relation to another time period or event, e.g., you took your shower before you got dressed. Relative time is founded on three major principles:

  1. Superposition: As geologists began studying the layers of rock, they deduced that the layers are arranged in a time sequence, with the oldest on the bottom and the youngest on the top, unless later processes disturb this arrangement.
  2. Uniformitarianism: In order to determine Earth’s past, geologists acknowledged that the same processes that shape the earth occurred in the past as they do now, and that the same laws of physics apply in all parts of the knowable universe.
  3. Fossil correlation: Also referred to as biostratigraphy, this is the science of dating rocks by using the fossils contained within them. Usually the aim is correlation, that is, demonstrating that a particular layer in one geological section represents the same period of time as another layer at some other section.

Absolute time is a precise time when an event occurs. For example, you took your shower at 7:30 a.m. for five minutes and got dressed at 7:40 a.m. The addition of absolute time to the Geological Time Scale was only made possible after the advent of radiometric dating during the first half of the 20th century allowed for more precise dating of rocks.

Radiometric dating : With the discovery of radioactivity in 1896, geologists were able to date rocks precisely using radiometric dating. This technique is used to date rocks based on a knowledge of the decay rates of naturally-occurring isotopes and their current abundances.

Supplementary Reading

To further your knowledge on radiometric dating, click here: Fundamentals of radiometric dating.

Enrichment Icon

Complete the following research on four principal contributors to the Geological Time Scale: Geological Time Scale Contributors.

Part 2: Understanding Geological Time Activities

Drop BoxComplete the following activity and submit the 2nd part to Mr. Durk either in person, or scan and email him a copy of the assignment. 

1. Pick one geological time period or epoch (i.e. Jurassic) from any of the geological time periods. List and describe three major biological events and three major geological events that occurred during that time period. Provide an explanation and synopsis of one of these events. Be sure to provide a list of websites / sources that you used.

2. Complete the Online Activity - Geologic Time

2. Complete the Assignment: Understanding Geologic Time using a Football Field (submit to Mr. Durk - hard copy).


  1. Comprehending Geologic Time Scale

Unless otherwise indicated, all images in this Activity are from the public domain or are © or Microsoft clipart and are used with permission.
This is a disclaimer. External Resources will open in a new window. Not responsible for external content.