Geology - Geologic Time Scale

 Geology - Geologic Time Scales

"Time is a dressmaker specializing in alterations."
            ~ Faith Baldwin

When examining the process of geology, an appreciation for the immense expanses of time involved is necessary. Non-geologists often have a hard time understanding that the processes on our planet Earth have been going on for over 4.5 billion years. Perhaps the reason time scales on the geologic level are difficult to comprehend is because we are accustomed to understanding and appreciating time scales on a human level, in which the lifespan is usually less than 100 years.

In addition, most of the processes of geology cannot be readily observed. Catastrophic events, such as an earthquake, a landslide or volcanic eruption, are highly visible and exciting, but most other processes require careful examination of our natural landscape.

Guiding Questions:
    1. Understand the time scales associated with geology by using the terms: Eon, Era, Period, Epochs, Stages (Ages), Ma and Mya.
    2. Explain why and how geologic time is divided.
    3. Understand the relationship of time between the formation of Earth and the advent of life.
    4. Determine the differences of relative and absolute dating methods and how they have contributed to modern day geologic theories.
The Division of Time

Please review the two graphical representations of geologic time. Pay attention to two aspects of each time geologic time scale: 1.) The names used and 2.) The divisions of each geologic time scale.

This graphical geologic time scale is from wikipedia.
The second graphical geologic time scale is from the International Commission on Stratigraphy (ICS) T
o learn more about the ICS click here

Let’s journey through the history of Earth by using the web-site created by the University of California Museum of Paleontology (UCMP).
    • Open the page
    • Read the article
    • Also please read the articles for Nicolaus Steno and William Smith
Ma and Mya -- What do they mean?

They both stand for the same thing; Millions of Years.

Naming Time

We will now continue on with the geologic time scales using the UCMP on-line exhibit to further explain how geologists named the respective Eons, Eras, Periods, Epochs and Ages.
  • Please use this LINK to return to the main page of the on-line exhibit “Tour of Geologic Time”
  • Use this LINK to view the next page which is called “Explore a specific period of time that interests you.”
    • First check out the LINK at the top of the page entitled “Navigating Our Geology Wing”. This will explain how the proceeding pages are designed and what all the features and buttons are for.
    • Work through the geologic time scale by starting at the bottom of the page and working towards the top or the ‘present’.
      • Read the information for each Period and Epoch represented on this page.
      • Note the time span for each Period and Epoch.
      • Pay particular attention to the “Event or Events” that characterize each Period and Epoch.

Thus far we have looked at the terms, how and why geologic time scales are designed. We will now use the USGS publication "Geologic Time" to discover the process and science behind relative and absolute dating techniques.
  • Please use this LINK for the USGS publication "Geologic Time". We are going to skim through this entire publication.
  • This is going to be the first place that there is a powerpoint attachment. It may take some time to upload these.

    • "Relative Dating" Power Point
    • "Radiometric Dating" Power Point

At This Point - Proceed to the next sub-topic: AP Notes Geologic Time