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T
he Earth solidified 4.6 billion years ago. Life has been evolving on Earth for more than 3.5 billion years.
These are time spans that are difficult to comprehend. Our limited experience with time involves years
grouped into decades and centuries – not millions or thousands of millions otherwise known as a billion years! To
understand geologic and biologic origins we can try to represent time concretely by converting time into a linear
dimension with a scale that is more manageable. Scaled time lines can be used to represent changes in a more
usable context. In this activity, you will construct a scale model of the major geologic and biologic events in
Earth’s history. You will do this to help yourself gain a sense of perspective with respect to the time it have take
for certain events to originate.
Procedures: Just like on tests, you need to READ the directions/questions carefully.
1. Review the data tables that accompany this activity. You will notice that the “Distance From Present (cm)”
columns are blank. You will be completing some math problems to fill these in PRIOR to creating the model.
2. Mathematical Parameters
a.) Your model will be 4.6m long. This distance equals 460cm.
b.) Your time line will cover 4,600 million years (4.6 billion years = 4,600,000,000 years)
c.) As a result, each cm of distance on your model will equal
years. Based on this scale, each
mm of distance will equal
years.
d.) To fill in the “distance from present” column, you must convert the data found in the “Millions of Years
Ago” column to a unit of distance. The formula for this conversion is as follows:
Value to be converted (in millions of years) x
1 cm
= Distance from Present (cm)
10 million years
e.) Example: the first conversion on the Geologic Time Scale requires you to convert 1.6 million years to
distance. Using the formula above the conversion would look like this:
1.6 millions of years x
1 cm
1.6
=
= 0.16 cm
10 million years
10
3. Working in groups of 4, get a 4.6m x 3in strip of paper.
4. Record your names, and your period on the inside, and outside of the strip. When you re-fold your model,
make sure that your name and period notation is visible.
5. Using colored pens/markers create a scaled model of the events since earth solidified 4.6 billion years ago.
Use the data found on the three data tables to properly label your time line model. You will include:
a. Geologic Time Scale
b. Major Geologic events
c. Biologic events
6. Divide you strip of paper down the middle for the entire 4.6 meters. Use the top area of your strip to record
the Geologic Time Scale – using the lower half of the strip for the Geologic and Biologic Events.
7. Additionally, you may personalize your group’s time line by adding pictures and color to your time model.
8. You will have approximately 50 minutes of class time to complete this project – so divide tasks among
yourselves in an efficient manner. Watch the clock, and keep on task. For example, you might want to work
together on the conversions for Table 1 so everyone understands. Then two people can start labeling the
model while two others complete the rest of the rest of the conversions.
9. You must finish timelines and questions today.
D ata Tables
Geologic Time Scale: Table 1
Era
Cenozoic
Period
Quaternary
Tertiary
Mesozoic
Cretaceous
Jurassic
Triassic
Beginning Time
Distance
(Millions of Years
from
ago)
Present (cm)
1.6
66.4
144
208
245
Permian
Carboniferous
Devonian
Silurian
Ordovician
Paleozoic
Cambrian
Pre Cambrian
286
360
408
438
505
570
4600
Major Geologic Events: Table 2
First Evidence of . . .
Land bridge between North and South America
Mississippi River
separation of Antarctica and Australia
collision of India with Asia and formation of the
Himalayan Mountains
formation of the present Rocky Mountains
breakup of Pangaea and formation of Atlantic
Ocean
formation of the supercontintinent Pangaea
extensive coal deposits
free oxygen nears present levels (1-20 percent)
an atmosphere and hydrosphere
the earth as a solid planet
Millions of Years Distance from
Ago
Present (cm)
5.7
35
50
55
70
165
225
350
600
3800
4600
Major Biological Events: Table 3
First Evidence of . . .
modern humans (Homo sapiens sapiens)
"Lucy" (Australopithecus afarensis)
members of the human family (hominids)
primates
flowers
birds
mammals
dinosaurs
reptiles
amphibians
land plants
vertebrates (jawless fishes)
animals with hard shells (marine invertebrates)
animals (soft-bodied marine invertebrates)
cells with a nucleus (eukaryotes)
life (bacteria)
2
Millions of Years Distance from
Ago
Present (cm)
0.04
3.2
4
65
140
150
225
235
300
360
430
520
590
680
1400
3500
Scaled Time Line
Geological Timeline Review Questions
1. Approximately what percentage of the Earth’s history has had life present?
2. For how many years were single-celled organisms the only kind of life on Earth?
3. If you consider the Earth’s entire known history, were dinosaurs a recent or ancient
group of animals on Earth?
4. Did mammals appear before, during, or after the dinosaurs? Which group has existed
the longest?
5. What may have led the mammals to spread and diversify beginning 65 million years
ago?
6. Did you have difficulty plotting any of the events on the list? If so, why?
3
Scaled Time Line