Viewing the Geologic Timeline from the Perspective of Integrated Science
by Stephen R. Mattox and Lisa M. Richardson
Department of Geology
Grand Valley State University
Allendale, MI 49504
mattoxs@gvsu.edu
ABSTRACT
Construction of a geologic timeline is a common activity in K-8 classrooms and in the
training of preservice teachers. The procedure is well described in Teaching about
Evolution and the Nature of Science (National Academy Press, 1998). The activity is
commonly viewed through the prism of biology with fossil organism displayed across the
spectrum of geologic time. We have developed complimentary timelines that emphasize
the significant events of and interconnectedness between the atmosphere, solar system,
and geosphere. Some key conditions/events/processes we feature include: differentiation
of the Earth; formation of the Moon; changes in cratering rates; early, nitrogen-rich
atmosphere; volcanism on the Moon; oldest mineral, rock, and fossil; geologic evidence of
atmospheric composition; gradual increase but low abundance of oxygen; presence of
ozone and abundant oxygen as life emerges onto land; coalescence and dispersal of
Columbia, Rodinia, and Pangaea supercontinents and resultant effects on species
distribution; impacts; mass extinctions; Ice House and Hot House climates; and high
carbon dioxide levels. We will present results assessing if the activity encourages a more
holistic view of the Earth history
Classroom discussion guides the students to mark off a timeline on adding machine
tape at a scale of 1 meter equals one billion years (1 cm = 10 million years). We divide
the class into four groups that construct four timelines (combined below). Each group
receives and envelope with photos/text of events and their time of occurrence. Student
tape their timelines on the blackboard and then tape their photos/text at the appropriate
time. Events/text are color coded to facility recognition and discussions: exosphere,
geosphere, hydrosphere and atmosphere, and biosphere.
Grand Valley State University offers an undergraduate degree in Integrated Science to
prepare future K-8 teachers. The program requires 12 credits each in biological, physical
and Earth/space sciences. Although this framework is well suited to convey the basics of
each field, little time is available to highlight the connections between the exosphere,
geosphere, hydrosphere and atmosphere, and biosphere across geologic time.
Many states require teachers to explain how rocks and fossils are used to determine the
age and geologic history of the earth. One method of presenting this information is the
construction of a geologic timeline by the students. The procedure is well described in
Teaching about Evolution and the Nature of Science (National Academy Press, 1998).
Although the timeline commonly shows a biological perspective we believe students will
benefit from looking at other important events in the history of the Solar System and
placing events in relative order and in context to previous and subsequent changes.
To guide students towards a more holistic view we have constructed a new timeline
that presents major events in the exosphere, geosphere, hydrosphere, atmosphere, and
biosphere using geologic time as the canvas.
4.6 Ga
Problems
● Students enter the class with little prior knowledge; thus, many of
these observations come as revelations.
● There is a large amount of data in a short class period.
● Some events shown as pinpoints in time, not as spans.
● How to assess?
● What did we miss?
● Permission to use photos/diagrams.
RESULTS
Some key points to raise with students:
● early differentiation, oceans, atmosphere…life
● accumulation of oxygen in atmosphere
● biological changes following changes in
ocean/atmosphere controlled by geosphere/hydrosphere
● plate tectonics influences species distribution
● singular events (differentiation, bombardment) vs.
cycles (Ice House, super-continents…extinctions)
In the classroom, students constructed four timelines
and then compared events from four perspectives.
Oceans form
N2 -rich
●
●
atmosphere
differentiation
●
●
1st prokaryote cells
●
●
●
O2 still being
added to oceans
●
●
1st Ice House
Photosynthesis
adds O2 to
oceans
●
Stromatolites
thrive
Lunar volcanism
2.6 Ga
1.6 Ga
No free O2 in
atmosphere
Oldest mineral
3.6 Ga
Oldest fossils
Possible Solutions
● Fred Mackenzie’s Our Changing Planet An Introduction to Earth
System Science has an excellent chapter on “Evolution of Planet
Earth” that would make a useful reading assignment.
● Keep the timeline visible in the classroom and refer back to it
frequently.
● Train our peers in astronomy, meteorology, and biology to stress
connections and to take the long view.
Increments of 100 million years
Moon forms
Earth forms
Student Comments
● “I always felt there were connections between the different
spheres but never really thought about it much until now.”
● “There is a pattern of connectivity between all the areas of
science. One sphere couldn’t exist without the preceding events in
other spheres occurring.”
● “I’m surprised at how long it took for prokaryotic cells to evolve
into organisms; I always assumed prokaryotic cells didn’t come
into existence until much later in earth’s history. I also never
learned that there was more than one super continent, but am very
interested to learn more about the two that formed before Pangaea.”
● “There’s a lot of information introduced all at once, so you can
get a few very general ideas before you go into information
overload.”
● “Everything about the time scale is surprising to me. 4.6 Billion
years is an unimaginable amount of time and scientists’ figuring out
what was going on back then is amazing.”
● “I didn’t know that the earth was so old.”
METHOD
INTRODUCTION
Intense
bombardment
DISCUSSION
Banded-iron
deposited
All Fe in oceans
deposited, O2
released to
atmosphere
●
●
O2
Gradually increasing
●
●
layer forms
Columbia
supercontinent
●
●
Stromatolites
still thrive
1st eukaryote cells!
●
Ozone
Dry land is
●
O2 ~10%
lifeless
Rodina
supercontinent
Copernicus forms
Oldest
multicellular
fossils
●
Hard
shells
Fish
Land
plants
2nd Ice House
Current glacial
Mammals
Extinction
0.6 Ga
Extinction
3d Ice House
Tetrapods
●
●
Pangea
supercontinent
Dinosaurs
Humans