CHAPTER INVESTIGATION
Geologic Time
OVERVIEW AND PURPOSE Geologists use information
from rocks, fossils, and other natural evidence to piece together
the history of Earth. The geologic time scale organizes Earth’s
history into intervals of time called eons, eras, periods, and
epochs. In this investigation you will
• construct a model of the geologic time scale
• place fossil organisms and geologic events in the correct
sequence on the timeline
Procedure
Complete the geologic time scale conversion chart. Use the conversion 1 mm = 1 million years to change the number of years
for each eon, era, period, and epoch on the chart into metric
measurements (millimeters, centimeters, and meters).
MATERIALS
• geologic time scale
conversion chart
• adding-machine paper
5 meters long
• scissors
• colored markers, pens,
or pencils
• metric tape measure or
meter stick
• sticky notes
Lay the adding-machine paper out in
front of you. At the far right end of the
strip write “TODAY” lengthwise along
the edge.
Starting from the TODAY mark, measure
back 4.6 meters, or 4600 million years.
Label this point “AGE OF EARTH.” Cut off
excess paper.
step 4
Fold the paper in half lengthwise and then
fold it in half lengthwise again. Unfold the
paper. The creases should divide your
paper into four rows.
At the far left end of the strip, label
each of the four rows as shown.
Using the numbers from your chart, measure
step 5
each eon. Start each measurement from the
TODAY line and measure back in time. For example,
the Archean eon started 3800 million years ago, so measure
back 3.8 meters from today. Mark that distance and write
“ARCHEAN EON.” Do the same for the other eons.
step 6
ARCHEAN EON
3800 million years ago (3.8 meters)
AGE OF EARTH
310 Unit 2: The Changing Earth
TODAY