Lesson Plan

Geology, Relatives, and Time

volcanic tuff, family tree, clock

NPS photo

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Grade Level:
Fifth Grade-Twelfth Grade
Earth Science, Geology
30 minutes
Group Size:
Up to 36
National/State Standards:
National Science Education Standards: Content Standard D
State Standards:
Idaho 8-9.ES.4.1.2
Utah 8.IS.III.3a
Wyoming 5-8.ES&PS.9
geologic time, geology, genealogy, family tree


Using a simple three or four generation family tree, students construct a relatives time tree that mimics the major divisions of the geologic time scale, Precambrian, Paleozoic, Mesozoic, and Cenozoic.


Students will:
Use science process and thinking skills
Demonstrate understanding of science concepts and principles.
Communicate effectively using scientific language and reasoning




In any science, a common lexicon is essential for ease of communication among peers. Geology is no exception; but being an historical as well as a descriptive science, it is important to have a universal understanding of time. The geologic time scale provides geologists the world over with a shared time reference. You might say that the geologic time scale is to geoscientists what the periodic table of elements is to chemists.

The geologic time scale is divided into eons, eras, periods, epochs and ages with eons being the longest time divisions and ages the shortest. Many of the period names have historical precedents dating back to the 18th and 19th centuries when outcrops of rock across Europe were being systematically mapped using the rules of relative timekeeping (original horizontality, original continuity, superposition, cross-cutting relationships and faunal succession). In accordance with these rules, the geologic time scale is arranged so the oldest time divisions are at the bottom and the youngest are at the top. It was not until the twentieth century that absolute ages could be assigned to the geologic time scale using radiometric dating techniques. Even now these absolute dates occasionally undergo minor revision.

By contrast a family tree can be divided into generations with the grandparents representing the roots; parents, aunts and uncles the trunk; siblings and cousins the branches; and sons, daughters, nieces and nephews the leaves. Events like births and marriages can be used to further sub-divide the generations much as periods are a subdivision of eras. And just as radiometric dating techniques provide absolute ages for the geologic time scale, birth certificates and marriage licenses document our family trees.


For this lesson you will need a simple three or four generation family tree prepared by each student and a geologic time scale. The following examples are needed for instructional procedures (steps 1-5).

Simpson (Dad) Family Tree (step 1)
Simpson (Mom) Family Tree (step 1)
GeologicTime Scale (step 2)
Simpson (Dad) Family Time Tree (step 4)
Simpson (Mom) Family Time Tree (step 4)
My Relatives Time Scale (step 4)
Geologic Time Scale 2008 (step 5)
My Relatives Time Scale (number 4 of assessment)




1. Geologists refer to the history of past events and life preserved in the rocks of Earth as the geologic record. Write a short family history, a family record, detailing the most significant events in the lives of your immediate relatives.

2. Take a closer look at your family time tree and the geologic time scale. Notice how a generation of your family time tree equates to an era, one of the longest divisions of geologic time, but that the geologic time scale also contains several smaller subdivisions of time called periods, epochs and ages. These individual time intervals often mark significant events in Earth history such as the appearance or disappearance of a biological organism (preserved as fossils) in the geologic record. Review what you have written about in your family record. How would you subdivide the generations (eras) of your family time scale into smaller time increments like the periods on the geologic time scale?

3. Prepare a My Relatives Time Scale of your extended family (grandparents, parents, brothers, sisters, nieces and nephews). Remember that the oldest event should be recorded at the bottom followed by progressively younger events. Remember relative time units often mark the first appearance of a biologic organism. This would be similar to what event in your life?

4. Take another look at the geologic time scale. Notice that an absolute (numerical) age has been assigned to the beginning of each eon, era, period, epoch and age. These have been determined by a variety of methods, the most common of which is the radiometric dating of igneous rocks. Think of radiometric dating methods as providing a birth certificate for the rock, much like the one issued to your parents when you were born. Geologic ages are recorded in years before present, so that the Precambrian began 4,567 million years ago. Assign an age to the beginning of each era and period of your family time scale. See My Relatives Time Scale for an example.


geologic time, Precambrian, Paleozoic, Mesozoic, Cenozoic, generation

Last updated: February 24, 2015