geologic time scale activity
introduction
understanding geologic time is critical to relating events in earth’s history to those of today. scientists use several forms of the geologic time scale to classify the age of objects and to become familiar with other events occurring simultaneously.
materials
if you would like to create your geologic time scale by hand, you will need the materials listed.
note: there are alternative procedures that do not require these materials.
● adding machine paper, or pieces of paper taped together to form a continuous line
● ruler or meter stick
● tape
● colored pencils, crayons, or markers
● digital camera, mobile device, or laptop camera to take a photograph of your time scale
procedures:
1. cut a piece of adding-machine tape approximately 4.6 meters long or attach pieces of paper in a continuous line using tape so it is approximately 4.6 meters long.
2. tape the ends of your paper onto your table so it is easier to measure and label.
3. label your paper “geologic time scale” at the top left.
4. at the top right of your paper, include the following scale:
1 meter
1 billion geologic years (1 bya)
1 centimeter
10 million geologic years (10 mya)
1 millimeter
1 million geologic years (1 mya)
5. starting from the left side of the paper, measure 5 centimeters to the right and draw a vertical line. label the line “today”.
6. plot each era, period, and important event on the paper using the scale provided and table 1 below.
7. when you have completed your geologic time scale model, take an image of it and place it into this document for your instructor to view.
procedures without materials:
there are many different types of models. a timeline is one way to represent the geologic time scale, but there are other ways as well. for example, an organization chart can show the progression of time to an approximate scale.
1. use the chart below to create your geologic time scale model. you may delete sections, add sections, and change the size of sections according to the approximate length of time you want to represent. a section of the geologic time scale is started below.
table 1
time
scale
major event
hadean eon
(precambrian time)
4.6 bya
4 m 60 cm
formation of earth and moon
archaean eon (precambrian time)
3.5 bya
3 m 50 cm
the first bacteria appear.
proterozoic eon (precambrian time)
2.4 bya
2 m 40 cm
rise in oxygen levels
550 mya
55 cm
the oldest marine worms and jellyfish appear.
phanerozoic eon- paleozoic era
440 mya
44 cm
the first fish and land plants appear.
395 mya
39.5 cm
the first amphibians appear.
380 mya
38 cm
the first insects appear.
phanerozoic eon- mesozoic era
240 mya
24 cm
the first dinosaurs appear.
220 mya
22 cm
the first mammals and birds appear.
65 mya
6.5 cm
dinosaur extinction
phanerozoic eon- cenozoic era
50 mya
5 cm
first horse
33 mya
3.3 cm
first apes
100,000 years
1 mm
the oldest humanlike ancestors appear.
the present
today
0 cm
reflection questions
1. how long (in centimeters and years) was the precambrian period compared to the rest of the scale?
2. how many years and “centimeters” of time separated the dinosaurs and humans on earth?
3. how many years and centimeters of time passed before life appeared on earth?
4. for how many years of geologic time have humans existed?
5. did dinosaurs exist at the same time as mammals? explain your answer using the geologic time scale.
6. what is the purpose of making a geologic time line? how do geologic timelines scientists?